# Cavitation issues



## warno (Jan 11, 2018)

When my boiler reaches anything over 195°F my circ begins to cavitate really bad. I don't believe it's pulling air down into the supply because the port is 8-9" below the surface of the water. I've been told it's called "net pressure suction head", is that what I'm experiencing?  What is the best way to alleviate the problem? 

Here's a picture of my supply port locations. I'm only using the one to the left of the flue exit.  It's a 1" port. 







And here is where my circ is located. Never mind the mess this was during the summer when I was changing things. 








Any help would be great thank you.


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## hondaracer2oo4 (Jan 11, 2018)

Unfortunately I think you fix is swapping the supply and return and pull the supply off the bottom. Your pump is cavitating I believe because as you reduce the inlet pressure on the intake side of the pump your actually reduce the boiling point of water. So I think being so close to 195  you are causing the water to flash steam as it enters the eye of the impeller and thus cavitate.


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## maple1 (Jan 11, 2018)

I was going to say try to mount the circ lower - but with 195 supply, a couple of feet likely might not make a difference.

Maybe you could T in that bottom left port too, and pull from both left ports? I was also going to suggest a mixing valve at the T, so it wouldn't pull too much cold in - but that might present enough head to also add some cavitating effect. So maybe T that port in but leave the ability to partly throttle it with a ball valve?


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## Golovkin (Jan 11, 2018)

I would mount the pump lower and T the other port into the inlet using a larger inlet size. I'm not well educated on this so, don't take my word on it. I just read somewhere when setting up my garn that I should mount the pump as low as possible and have my supply line larger than my return to reduce cavatation at high temps. - don't take my word for it, but its something for you to look into.


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## warno (Jan 11, 2018)

Would making the supply port significantly bigger help any? Being it's on a homemade unit there's no warrantee to void if I change things up. If i run a 1.25" supply line or 1.5" line then bush it down to 1.25" just before the circ inlet. And also put the circ as low as possible?


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## 3fordasho (Jan 11, 2018)

Ran across this in the Garn system design manual, may be useful.


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## Fred61 (Jan 11, 2018)

I Know next to nothing about this so I have no suggestions. The guys in the know that have posted here have had several good suggestions but none have suggested pumping toward > the boiler. Can that not be done?


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## warno (Jan 11, 2018)

Fred61 said:


> I Know next to nothing about this so I have no suggestions. The guys in the know that have posted here have had several good suggestions but none have suggested pumping toward > the boiler. Can that not be done?



You mean move the pump to the return side? If so, it absolutely can be done I just thought the "pumping away" method was the preferred method.


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## Fred61 (Jan 11, 2018)

warno said:


> You mean move the pump to the return side? If so, it absolutely can be done I just thought the "pumping away" method was the preferred method



That's what I meant. Seems like several years back. To me that's more than 55 years back all the systems pumped toward the boiler. That's when circs were more susceptible to damage from heat so they were put on the cooler return side. Hopefully someone with more knowledge about this will chime in.


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## hondaracer2oo4 (Jan 11, 2018)

Fred, on a closed pressurizzed system that works fine because water is just being spun in a loop and the pump can’t cavitate from lack of water on the suction side because the pump can only push out what it can pull in. On an open system if you had a 5 inch line on the discharge side and a 1 inch on the supply side you would cavitate all day long because you would never be able to supply the pump with enough water compared to the head pressure presented to it on the discharge side. 

Yes warno if you can increase the size of the supply port to the pump you should be able to stop the cavitation. Bottom line is the vacuum bearing created on the supply side of the pump because of restricted flow is lowering the boiling point of water to at or below 195 causing the water to flash steam as soon as it enters the vacuum st the eye of the impeller.


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## warno (Jan 11, 2018)

hondaracer2oo4 said:


> Yes warno if you can increase the size of the supply port to the pump you should be able to stop the cavitation. Bottom line is the vacuum bearing created on the supply side of the pump because of restricted flow is lowering the boiling point of water to at or below 195 causing the water to flash steam as soon as it enters the vacuum st the eye of the impeller.




How big of supply port would you suggest? I really want to get this figured out because next year I'm planing on pushing 200 degrees in the boiler to help charge my storage. So if i can avoid this caviation problem that'd be great.


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## hondaracer2oo4 (Jan 11, 2018)

What size is the supply pipe off the boiler currently? I think I would go with 1 1/2. I would honestly try pulling off the bottom first and see if you solve the issue. I would just use 1 inch truck heater hose to temporally hook it up and see if the cavitation goes away. This would be cheap and easy.


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## warno (Jan 11, 2018)

hondaracer2oo4 said:


> What size is the supply pipe off the boiler currently? I think I would go with 1 1/2. I would honestly try pulling off the bottom first and see if you solve the issue. I would just use 1 inch truck heater hose to temporally hook it up and see if the cavitation goes away. This would be cheap and easy.



The ports are currently 1". 

In order to hook into the bottom port I'll have to break everything down. And if I'm going that far then I'm god with just putting on a bigger port. Unless you think there's a chance it would fix the issue.

If you think going 1.5" supply line will do it then I'm good with that. Pipe and fittings are cheap to me, to the tune of scrap costs. And the TIG welder in the garage is happy to glue it all together.


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## heaterman (Jan 11, 2018)

I take it your boiler is not a sealed type you can maintain any pressure in?
If so, you're going to find 180-185* is the maximum temperature you can run without destroying pumps.
Also keep in mind that the higher the "head" is in the piping the more NPSH you need to maintain on the inlet of the circ.
Larger diameter tube on the discharge side is the only thing that will accomplish that all other factors being equal.

Think of head this way...  1' of head is developed by a column of water obviously 1' above the point of measurement.  In your case, the suction inlet of the pump.
Until you reach the point where the piping on the suction side cannot flow enough to satisfy the pump, inlet pipe size is immaterial. 
Whether you use 1" pipe or 4" pipe on the inlet side, a vertical foot of height above the pump still equals only 1' of head pressure.


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## warno (Jan 12, 2018)

heaterman said:


> I take it your boiler is not a sealed type you can maintain any pressure in?
> If so, you're going to find 180-185* is the maximum temperature you can run without destroying pumps.
> Also keep in mind that the higher the "head" is in the piping the more NPSH you need to maintain on the inlet of the circ.
> Larger diameter tube on the discharge side is the only thing that will accomplish that all other factors being equal.
> ...




It is an open system boiler.

So you're saying that even with a bigger supply line to the suction side of the circ I'll probably still have this issue? I'm running alittle under 20ft of head for this pump on my boiler. Do you think there's any way to over come this issue at all?

Edit: I guess you did say a larger pipe on the discharge would help.


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## jwise87 (Jan 12, 2018)

On my last homemade system I pulled off the bottom on a open system with 3/4 ports and didn't have cavitation issues even when my water would occasionally get above 200*, so I would put it at the bottom and see if that helps. If I recall correctly you run a rather small water jacket, so if your pump is running all the time your temp differences should be negligible from top to bottom, as long as you have good circulation in the jacket.


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## tom in maine (Jan 12, 2018)

The usual way on a closed system, to prevent this, would be to increase the pressure at the pump. This suppresses the cavitation bubbles from forming in the impeller, where localized boiling is occuring.
In an unpressurized system, only the standing head does this. You might try installing an open (small opening) pipe and/or reservoir higher than the high point on the system. This would still keep your system open and relatively safe (if that is what you were going for) but increase the pressure at the pump.

BTW, nice welding!


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## maple1 (Jan 12, 2018)

Where and what is the vent to atmosphere on your boiler? Can you extend that up? Pipe in an open higher up 'expansion' tank? Wouldn't have to be all that big.


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## Hydronics (Jan 12, 2018)

I'm assuming this is an outdoor unit with a long loop between buildings, correct? Bear in mind that the major pumping loss is the friction loss in the underground piping which looks to be only 1". The suction side losses cause the NPSH issue. Upsizing a few feet at the boiler alone will do little to improve NPSH.
If I understand your setup, I'd say you have the following options to reduce cavitation:

increase underground pex size to boiler to reduce friction losses
pressurize the loop (would require a HX if you can't pressurize the boiler)
decrease temperature (opposite of your intent to max storage)
decrease flow (smaller circulator)
a combination of all 4 above
Sorry to be the bearer of bad news...

Are you destroying impellers? If not excessive, it may last a long time this way.


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## warno (Jan 12, 2018)

maple1 said:


> Where and what is the vent to atmosphere on your boiler? Can you extend that up? Pipe in an open higher up 'expansion' tank? Wouldn't have to be all that big.



In this picture you can see the square box sitting on top of my water jacket. I call this "the bubble".






And inside that opening is a stand pipe that runs down and out the bottom.  that pipe is my vent line. 






I built it this way so the water could expand up into the bubble and if needed overflow out the stand pipe. Also this helps with evaporating loses. As far as making it higher, I could maybe go a few more inches before it gets too close to the cover. 



Hydronics said:


> I'm assuming this is an outdoor unit with a long loop between buildings, correct? Bear in mind that the major pumping loss is the friction loss in the underground piping which looks to be only 1". The suction side losses cause the NPSH issue. Upsizing a few feet at the boiler alone will do little to improve NPSH.
> If I understand your setup, I'd say you have the following options to reduce cavitation:
> 
> increase underground pex size to boiler to reduce friction losses
> ...



My boiler has 22 feet of thermopex under ground before entering my garage. Then it goes through a plate HX and back. With fittings and valves inbetween. 

This pump has been running for 2 seasons in it's current setup. It doesn't always get to the point of cavitation but if I over load the boiler then it does. It's not very often i do that but i know these pumps hate air in them so I'm trying to fix the problem now. 



Also I want to thank everyone for trying to help me out.


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## hondaracer2oo4 (Jan 12, 2018)

So I  confused by some of the previous comments. Can you guys explain why reducing the head presented to the pump on discharge side would cause the pump to not cavitate? Reducing the head on the pump would cause it to
Be able to move more water which would further starve the pump on the intake side for water which would increase the vacuum and drop the boiling point even lower. The pump has atmospheric pressure 14 psi pushing the water into the inlet.


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## tom in maine (Jan 12, 2018)

A vacuum forms at the impeller when the pump is operating. As the pressure drops below atmospheric, the boiling point drops. 
Higher pressure suppresses this.


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## hondaracer2oo4 (Jan 12, 2018)

Tom, yes I agree, that's what I posted above. But it was stated that increasing the pipe size on the discharge side of the pump would fix this but I don't follow how that would increase the pressure on the intake side of the pump. If the pump has less head loss on the discharge side then it is going to decrease the pressure even further on the intake side. Increasing the intake side of the pump size will allow more water to flow to the intake side of the pump under atmospheric pressure.


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## maple1 (Jan 12, 2018)

hondaracer2oo4 said:


> Tom, yes I agree, that's what I posted above. But it was stated that increasing the pipe size on the discharge side of the pump would fix this but I don't follow how that would increase the pressure on the intake side of the pump. If the pump has less head loss on the discharge side then it is going to decrease the pressure even further on the intake side. Increasing the intake side of the pump size will allow more water to flow to the intake side of the pump under atmospheric pressure.



I can't really explain why I am picturing this - but what I am picturing is me putting my hand over the outlet of Warnos circ, and that resulting in a swarm of bubbles appearing around his impeller.


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## maple1 (Jan 12, 2018)

warno said:


> In this picture you can see the square box sitting on top of my water jacket. I call this "the bubble".
> 
> View attachment 220482
> 
> ...



How hard or impractical would it be for you to make that box cover water tight, and plug that pipe. Then/and put an outlet on the cover going up (or on another convenient boiler tapping, if you have one - one of your unused ones on the back might work), connected to a small open tank up as high as you can practically get it. Thereby raising your water height & circ inlet pressure? It would increase about 0.4psi for every foot your water height goes up.


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## jwise87 (Jan 12, 2018)

The way I understand it is that there is already the maximum amount of water that can get to the impeller at 1 bar pressure right now, so increasing the intake side pipeing size won't help. Following that line woundn't throttleing the output side of the pump help? It would at least move the cavitation to the other side of the throttleing valve.


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## Marshy (Jan 12, 2018)

What is NPSH?

The margin of pressure over vapor pressure, at the pump suction nozzle, is Net Positive Suction Head (NPSH). NPSH is the difference between suction pressure (stagnation) and vapor pressure.

https://www.pumpsandsystems.com/topics/understanding-npsh-npsh-definitions

You need to understand that in order for the water to remain liquid and not turn to vapor, you need to remain above the required NPSH for the pump. The pump manufacture specifies the NPSHR (R=REQUIRED) and draws it on the pump curve. You can reduce the NPSHR by throttling the pump back on its curve (add restriction on the discharge) or by increasing the pressure at the inlet (ie pressurize the boiler waterjacket or lower the pump in relation to the waterjacket) or lower the temperature of the fluid.  Increasing the size of the supply piping will not be sufficient to eliminate the cavitation.


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## tom in maine (Jan 12, 2018)

Pipe diameter might have an impact on pressure around the pump. I do not know for sure.
I do know that if you can install what amounts to a small expansion tank that is still open to the atmosphere over the pump, the system is going to operate at a higher pressure, even though it is open, and the
pump impeller will cavitate less.
For safety sake, there would be no shutoffs between the boiler and that opening on the tank. The opening can be small.
And I would still have a pressure relief valve on the boiler shell.


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## Marshy (Jan 12, 2018)

So basically you have available NPSH which is determined strictly by the pressure of the boiler water jacket in pressurized systems plus the elevation difference between the pump and boiler, or by just the height difference between the pump and the top of the water level in the boilers jacket for unpressurized minus thread loss from the piping. The the length, size, roughness of and number of elbows in the pipe causes a reduction in the available npsh. What your left with is the systems total available NPSH. Increasing the size will increase the available NPSH but the difference in head loss is very minor between say 1-1/4" and 1-1/2" pipe. It may be enough to keep it from cavitating but not likely enough if he wants to incresasue the water temp up to 190 or even 200.


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## warno (Jan 12, 2018)

There is no room in the boiler shed to go upwards any higher. The bubble is basically rubbing the roof of the shed already. And there is no way to pressurize the boiler. Even with a safety pop off valve, there is far too much flat surface on my boiler too hold any pressure what so ever. 

 so it sounds like the only option left for me to try is pull supply from the bottom port of the boiler and run return back in the top. With this circ I'm running I think I'll still get good boiler mixing so that shouldn't be a problem. Where my lower port is located from the bottom I should have roughly 100 gallons of water above it. Would that be enough to help my issue? I know this was mentioned earlier in this thread. I wasn't ruling it out, just wanted to see if other options were available.


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## TCaldwell (Jan 12, 2018)

Are the supply and return lines where they go to your garage lower than your boiler elevation, if so could you move the circ to that location?


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## warno (Jan 12, 2018)

The boiler lines only flow to the plate HX. The HX is about half way up the boiler height, I'm guessing. I do have room in the garage for the supply circ, if that would work.


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## tom in maine (Jan 12, 2018)

The pressure created by a reservoir positioned above the rest of the heating system can be located remotely from the boiler. It just has to be higher than the rest of the system. The pressure developed by the water column is not really affected by the tubing diameter, I believe.


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## Marshy (Jan 12, 2018)

warno said:


> There is no room in the boiler shed to go upwards any higher. The bubble is basically rubbing the roof of the shed already. And there is no way to pressurize the boiler. Even with a safety pop off valve, there is far too much flat surface on my boiler too hold any pressure what so ever.
> 
> so it sounds like the only option left for me to try is pull supply from the bottom port of the boiler and run return back in the top. With this circ I'm running I think I'll still get good boiler mixing so that shouldn't be a problem. Where my lower port is located from the bottom I should have roughly 100 gallons of water above it. Would that be enough to help my issue? I know this was mentioned earlier in this thread. I wasn't ruling it out, just wanted to see if other options were available.


How many inches of water are above the port that the pump suction is hooked to? 

You could mount the pump horizontally down near the floor. That will provide a very small increase in available NPSH.  

 You could also convert to 1-1/4" or 1-1/2" pipe too the suction of the pump in an effort to reduce head loss to the pump suction.  Use large radius elbows out of the boiler and to the pump every where possible.  

If you have a 3 speed pump toy could try a slower speed.  

You could throttle the discharge flow some to get the pump run ball on its curve.  

Simply drawing from the bottom of your tank might not be helpful if the temp at the bottom of the boiler isn't much cooler than where your currently dreading from but it might be your best bet.  Temperature is your enemy in this situation.


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## Marshy (Jan 12, 2018)

TCaldwell said:


> Are the supply and return lines where they go to your garage lower than your boiler elevation, if so could you move the circ to that location?


This. You need to lower the pump and reduce the temp of the inlet. Enough of either one or a mix of both will solve the issue.


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## warno (Jan 12, 2018)

tom in maine said:


> The pressure created by a reservoir positioned above the rest of the heating system can be located remotely from the boiler. It just has to be higher than the rest of the system. The pressure developed by the water column is not really affected by the tubing diameter, I believe.



In a vented system it can't be above the vent line though, correct? Gravity would simply level it out, would it not?


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## maple1 (Jan 12, 2018)

warno said:


> The boiler lines only flow to the plate HX. The HX is about half way up the boiler height, I'm guessing. I do have room in the garage for the supply circ, if that would work.



You could T in a high open expansion tank in your boiler loop, if that goes to your garage. Not sure where your hx is.


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## maple1 (Jan 12, 2018)

warno said:


> In a vented system it can't be above the vent line though, correct? Gravity would simply level it out, would it not?



Yes true. Which means you'd need to seal up the boiler.


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## OT_Ducati (Jan 12, 2018)

What if you place the circulator next to the floor changing the orientation 90*?
Looks like you might gain some head and only ad a couple fittings. ?


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## Marshy (Jan 12, 2018)

Guys, the only way to prevent cavitation is to lower the temp of the water or increase the pressure of the water at the inlet of the pump.

The latter can be achieved by lowering the pump relative to the boiler or raising the boiler relative to the pump.

The things like increasing the inlet piping size, use of long radius elbows, adding some restriction at the oulet and running the pump are going to make very little difference because the pipe from the boiler to the pump are so short. Adding restriction at the outlet and running the pump slower will have the most effect.

Recommending changes to the piping between the boiler and pump like adding some sort of tank is pointless and will not work.


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## warno (Jan 12, 2018)

Marshy said:


> How many inches of water are above the port that the pump suction is hooked to?
> 
> You could mount the pump horizontally down near the floor. That will provide a very small increase in available NPSH.
> 
> ...




Theres about 8-9" of water above the supply port.  

I'm running a bell and gossett NRF-36 on the boiler. I was hoping to run it on speed 3 next year to help push btus through my plate HX. Also why I don't want to throttle the discharge much. Although that does work because the first time I heard the cavitation happening I throttled the discharge and it quit. 

The temperature problem sucks because I was hoping to run higher temps next year.


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## Marshy (Jan 12, 2018)

You would get the best bang for your buck of you mmmkoved the pump to just after the heat exchanger. The reduced temp would be a huge benefit. The down side is you would have to modify your system if you don't want constant flow through your htx.


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## maple1 (Jan 12, 2018)

Marshy said:


> Guys, the only way to prevent cavitation is to lower the temp of the water or increase the pressure of the water at the inlet of the pump.
> 
> The latter can be achieved by lowering the pump relative to the boiler or raising the boiler relative to the pump.
> 
> ...



But- adding a tank, higher up, would effectively be the same as raising the boiler. Wouldn't it? In order to add that tank you would have to seal the boiler up so water couldn't come out the top, though.


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## Marshy (Jan 12, 2018)

maple1 said:


> But- adding a tank, higher up, would effectively be the same as raising the boiler. Wouldn't it? In order to add that tank you would have to seal the boiler up so water couldn't come out the top, though.


Technicality yes,  as long as the boiler becomes sealed and you make the new high point open to atmosphere.  Unfortunately he had no overhead room. Its more practical to plumb the pump after the htx.


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## jwise87 (Jan 12, 2018)

If the only reason you need to run the high temps is to charge your storage, and you already have a second port your not using, you could buy a small cheap pump (Taco 007) that won't flow enough to cavitate and use it move water into the storage tank. I know that wouldn't be ideal and might require some creative plumbing, but it might be another option.


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## brenndatomu (Jan 12, 2018)

warno said:


> Theres about 8-9" of water above the supply port


That's precious little head pressure on the suction port. As stated previously, the water pressure will be .485 PSI per foot of water column above the suction port...doesn't matter if its a gallon, or 100 gallons, its all about the height above the pump.
Larger port and/or line would help some, lowering the pump would help, slowing it down would help, lowering the water temp would help.
Lowering the pump would probably help the most out of the choices here that you are likely going to be willing to actually try.
One thing you could do is to throttle a valve on the discharge side of the pump a bit...if it doesn't take much throttling to stop the cavitation, then it won't take much of a change to fix the issue permanently...until you raise the system temp anyways...you may be dealing with it again then...


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## warno (Jan 12, 2018)

I just went out to lite a fire and I grabbed some pictures of my current plumbing.

The boiler is located just outside my garage there's 22 feet of 1" thermopex in the ground. My Supply port is a 1" port and is 8" from the water level surface. The boiler is an open system. And I do batch burns to heat storage. The only time the boiler circ is running is during a firing cycle.

I'm getting conflicting ideas of things that will or won't work. If moving the circ down the the ground with a 1.5" suction side will get it done then I'm good with that. The only thing I can't change at this time is my underground lines. For 2 reasons, cost and a massive PITA to dig up and replace with bigger lines.

Here's a picture of the boiler side of things.












And here's inside the garage in the "plumbing closet". You can see the thermopex lines flow into the diverter valve then you the HX. The diverter valve flows to either the HX or the heat dump zone.


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## TCaldwell (Jan 13, 2018)

The Garn is the same idea just bigger in all respects, ports too however the manual states the circ needs to be as low as possible for the npsh factor. A little simplistic analogy but the same idea


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## Marshy (Jan 13, 2018)

warno said:


> I just went out to lite a fire and I grabbed some pictures of my current plumbing.
> 
> The boiler is located just outside my garage there's 22 feet of 1" thermopex in the ground. My Supply port is a 1" port and is 8" from the water level surface. The boiler is an open system. And I do batch burns to heat storage. The only time the boiler circ is running is during a firing cycle.
> 
> I'm getting conflicting ideas of things that will or won't work. If moving the circ down the the ground with a 1.5" suction side will get it done then I'm good with that. The only thing I can't change at this time is my underground lines. For 2 reasons, cost and a massive PITA to dig up and replace with bigger lines.


The reason it seems like you are getting conflicting ideas is because no one is 100% certain what will resolve it. 

If it was my system I would start with relocating the pump as low as I physically could. Reorient it so that it's horizontal and near the floor in the boiler cabinet. At the same time I would change the inlet piping to 1-1/4", including the flanged isolation valve at the inlet. Not much you can do for the welded outlet through the boiler jacket.


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## TCaldwell (Jan 13, 2018)

I agree with above but possibly not all that con flicking if rising a water column above the boiler ( not feasible) is really the same as lowering the circ.


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## warno (Jan 13, 2018)

Marshy said:


> The reason it seems like you are getting conflicting ideas is because no one is 100% certain what will resolve it.
> 
> If it was my system I would start with relocating the pump as low as I physically could. Reorient it so that it's horizontal and near the floor in the boiler cabinet. At the same time I would change the inlet piping to 1-1/4", including the flanged isolation valve at the inlet. Not much you can do for the welded outlet through the boiler jacket.



Ok I'll give that a shot. I'll drop the circ too the floor and increase the piping. I'll simply cut out the existing 1" port and weld in a new 1.5". Then I'll neck it down to 1.25" just before the circ inlet. I'll get a new isolation valve as well. I found this one on supply house.


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## brenndatomu (Jan 13, 2018)

Lowering the pump by itself will make no difference...the suction line must be moved to the bottom port to raise the head pressure on the pump.
Think about it like this, fill a 5 gallon bucket with water, drill a hole 1/2" from the top, weak stream right? Then drill a hole at the bottom...strong stream. A big difference in flow with only a ~15" difference in height...about a 0.544 PSI increase.
So moving the suction line to the lower port (even if its only a couple feet) can make a big difference.

(BTW, I said .485 PSI per foot water column height earlier...I meant .435 PSI per ft...oops )


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## hondaracer2oo4 (Jan 13, 2018)

Where is the thermal well for the aquastat mounted? Have you tried take a temp measurement of the top of the tank vs the bottom? With a 1 inch line you are probably pushibg 10 gpm in the stove. If the probe is mounted lower than the currently supply port you could have 200 * water r higher entering the pump putting you even closer to cavitation with very little drop in Npsh.


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## warno (Jan 13, 2018)

brenndatomu said:


> Lowering the pump by itself will make no difference...the suction line must be moved to the bottom port to raise the head pressure on the pump.
> Think about it like this, fill a 5 gallon bucket with water, drill a hole 1/2" from the top, weak stream right? Then drill a hole at the bottom...strong stream. A big difference in flow with only a ~15" difference in height...about a 0.544 PSI increase.
> So moving the suction line to the lower port (even if its only a couple feet) can make a big difference.
> 
> (BTW, I said .485 PSI per foot water column height earlier...I meant .435 PSI per ft...oops )



Would the lower port need to be bigger than 1"? Because right now it's also a 1" line. 



hondaracer2oo4 said:


> Where is the thermal well for the aquastat mounted? Have you tried take a temp measurement of the top of the tank vs the bottom? With a 1 inch line you are probably pushibg 10 gpm in the stove. If the probe is mounted lower than the currently supply port you could have 200 * water r higher entering the pump putting you even closer to cavitation with very little drop in Npsh.



The aquastat well is about 1" above the supply port.


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## brenndatomu (Jan 13, 2018)

warno said:


> Would the lower port need to be bigger than 1"? Because right now it's also a 1" line.


Larger certainly wouldn't hurt...but simply moving the line to the existing bottom port will be an improvement...will it be enough? Dunno...but I would think it would be pretty easy to try...with a helping hand I think you could do it without losing much water at all.


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## maple1 (Jan 13, 2018)

brenndatomu said:


> Lowering the pump by itself will make no difference...the suction line must be moved to the bottom port to raise the head pressure on the pump.
> Think about it like this, fill a 5 gallon bucket with water, drill a hole 1/2" from the top, weak stream right? Then drill a hole at the bottom...strong stream. A big difference in flow with only a ~15" difference in height...about a 0.544 PSI increase.
> So moving the suction line to the lower port (even if its only a couple feet) can make a big difference.
> 
> (BTW, I said .485 PSI per foot water column height earlier...I meant .435 PSI per ft...oops )



I'm not so sure about that. The overall thing that matters, is the height difference, between the circ inlet, and the top of the system water in the boiler. If you leave the pump where it is but tap in lower on the boiler, that won't change that height difference. It won't raise the head pressure.

It would likely lower the inlet temperature, which would improve cavitation issues - but that is a separate & different factor.

Your bucket analogy would apply, if the circ was up at the top hole. But it's not - it is connected to the top hole, by a pipe. That pipe height also adds head pressure.


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## Marshy (Jan 13, 2018)

TCaldwell said:


> I agree with above but possibly not all that con flicking if rising a water column above the boiler ( not feasible) is really the same as lowering the circ.



In order for that to work he would need to seal the vent from the boiler jacket, construct the pipe such that it comes out of the boiler jacket and raises as high as physically limited, then have a small tank (2.5 gal might be plenty) that is open to the atmosphere for venting, then pipe down to the suction of the pump. 




brenndatomu said:


> Lowering the pump by itself will make no difference...the suction line must be moved to the bottom port to raise the head pressure on the pump.
> Think about it like this, fill a 5 gallon bucket with water, drill a hole 1/2" from the top, weak stream right? Then drill a hole at the bottom...strong stream. A big difference in flow with only a ~15" difference in height...about a 0.544 PSI increase.
> So moving the suction line to the lower port (even if its only a couple feet) can make a big difference.
> 
> (BTW, I said .485 PSI per foot water column height earlier...I meant .435 PSI per ft...oops )



Your analog regarding the bucket is totally incorrect sir. So is your assumption that NPSH will increase if you relocate the suction port lower and leave the pump where it is. 

*Only way to increase NPSH is to increase the distance from the pump to the water level that is exposed to atmosphere.* Simply changing the suction port without lowering the pump does nothing to the NPSH. I know this because I have studied fluid mechanics.


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## brenndatomu (Jan 13, 2018)

maple1 said:


> I'm not so sure about that. The overall thing that matters, is the height difference, between the circ inlet, and the top of the system water in the boiler. If you leave the pump where it is but tap in lower on the boiler, that won't change that height difference. It won't raise the head pressure.
> 
> It would likely lower the inlet temperature, which would improve cavitation issues - but that is a separate & different factor.
> 
> Your bucket analogy would apply, if the circ was up at the top hole. But it's not - it is connected to the top hole, by a pipe. That pipe height also adds head pressure.


OK, easy to test this...stick a hose in the hole long enough to reach the ground...compare the top hole vs the bottom with the same length hose, both discharging at ground level...I think you'll find the lower hole flows much stronger (at least for a while )


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## Marshy (Jan 13, 2018)

maple1 said:


> ...
> ...
> Your bucket analogy would apply, if the circ was up at the top hole. But it's not - it is connected to the top hole, by a pipe. That pipe height also adds head pressure.


Yes, correct. It's the total height from the pump to the water line exposed to atmosphere. Thst is why you would have make the boiler "solid" ie pipe tight and raise the point where the system is exposed to atmosphere.


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## Marshy (Jan 13, 2018)

brenndatomu said:


> OK, easy to test this...stick a hose in the hole long enough to reach the ground...compare the top hole vs the bottom with the same length hose, both discharging at ground level...I think you'll find the lower hole flows much stronger (at least for a while )


All do respect, your analogy is poor and not applicable to this. I can cite references from my text books if you would like a course in NPSH. It will take me an hour to type out a correct analogy to explain it. The OP would probably dislike the derail to his thread. Plain and simple, the available NPSH is the height difference between pump and water level exposed to atmosphere. *Doesn't matter to the pump NPSH if the water jacket port is 8" or 20" below water level if the height between the pump and water surface exposed to atmosphere remains unchanged. *


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## warno (Jan 13, 2018)

terrible drawing I know but what about this. I change my upper suction port to 1.5" and run it to the floor and then somewhere in that line above the circ tie in my lower 1" port. I'll put a valve on the lower port to throttle the suction of that port. Then tie it all into my circ suction side. 

Red - new plumbing
Blue - ball and isolation valves
Yellow - circ


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## Marshy (Jan 13, 2018)

warno said:


> terrible drawing I know but what about this. I change my upper suction port to 1.5" and run it to the floor and then somewhere in that line above the circ tie in my lower 1" port. I'll put a valve on the lower port to throttle the suction of that port. Then tie it all into my circ suction side.
> 
> Red - new plumbing
> Blue - ball and isolation valves
> ...


Teeing into the 1.5" will do no good. And improvements will come from the increase in the suction pipe size and moving the pump lower. You might get some mixing of cooler water from the lower port though, it's uncertain how thst will really help you if you are trying to supply a higher temp to your htx. It might be counter productive to the temp being sent. Could try it. Worse case is you spend money on the fitting and end up leaving the 1" lower port closed.

Btw, if you are going to 1.5" to the pump,  get a 1.5" flanged valve to the pump,  don't step back to 1.25".


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## brenndatomu (Jan 13, 2018)

Marshy said:


> I can cite references from my text books if you would like a course in NPSH


No need...I'm not here to stir anything up...and I've read the same text books as you...work on pumps for a living...not an engineer, but have corrected more than a few engineering mistakes...gonna watch this one play out from the stands...


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## maple1 (Jan 13, 2018)

The T'ing in the lower port will help cavitation, but only in that it would allow you to pull in cooler water. Which would be counter to your real goal, which is to get hotter water to storage.

I think most of us are on the same page in all this stuff, just have different ways of saying things.


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## warno (Jan 13, 2018)

Marshy said:


> Teeing into the 1.5" will do no good. And improvements will come from the increase in the suction pipe size and moving the pump lower. You might get some mixing of cooler water from the lower port though, it's uncertain how thst will really help you if you are trying to supply a higher temp to your htx. It might be counter productive to the temp being sent. Could try it. Worse case is you spend money on the fitting and end up leaving the 1" lower port closed.
> 
> Btw, if you are going to 1.5" to the pump,  get a 1.5" flanged valve to the pump,  don't step back to 1.25".



Ok I was thinking about the idea of the lower port adding to the pressure form the higher water level on the lowered pump location.  basically the valve would be cracked open. But if it's not with it then i won't add it. 

I couldn't find a 1.5" flanged ioslation valve. I'll check again.


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## warno (Jan 13, 2018)

I guess when you search for one you can find it. 

Like this here


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## maple1 (Jan 13, 2018)

Ok throwing something sideways in. After looking at your hx area pic. Have you tried the dump circuit? I'm just wondering how good it would flow or not, because it looks like it goes up a lot higher than the boiler water level. Making for a good place for air to wander to and lock up. Maybe?


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## warno (Jan 13, 2018)

maple1 said:


> Ok throwing something sideways in. After looking at your hx area pic. Have you tried the dump circuit? I'm just wondering how good it would flow or not, because it looks like it goes up a lot higher than the boiler water level. Making for a good place for air to wander to and lock up. Maybe?



The dump zone does work and there's an auto air vent on the water/air HX up there. But that's irrelevant because I'm changing my dump zone. I'm  moving it down to right next to the plumbing in the cabinet.


Here's the dump coil


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## Fred61 (Jan 13, 2018)

What's the diameter of the pipe that drains the "bubble"?

Sent from my SM-G900R4 using Tapatalk


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## maple1 (Jan 13, 2018)

Ok - sideways, and not relevant, will forget that. Just something that came to mind when I saw the pic.

But hearing that you are going to be replumbing that area some, and stepping back a bit - how ugly a job would it be to move your HX, and put the boiler circ in there with it? Like, move the HX down, to close to the level of where the undergound comes in. And put the circ on the return side of the HX? Per Marshys earlier suggestion? At first, after seeing that pic, I was going to just suggest moving the circ there, to right before where the return lines goes underground. Vertically. That being the lowest point between the HX and where it goes back underground. But it might not be easy to mount it right there. So if you also move the HX down to that level, you might create a piece of solid horizontal piping you could mount the circ into more easily. And you would get everything below your boiler water level. Said without knowing exactly the height difference between your HX & boiler water level. But I think getting the circ where the water is coolest (after the HX) will do the most for the cavitation issues in your situation of wanting the most heat to storage you can get & not having much leeway in increasing your circ inlet pressure.

Not sure I said all that the right way, but hopefully with everything everybody is throwing at you, you can find a tidbit or two to help.


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## Marshy (Jan 13, 2018)

maple1 said:


> Ok - sideways, and not relevant, will forget that. Just something that came to mind when I saw the pic.
> 
> But hearing that you are going to be replumbing that area some, and stepping back a bit - how ugly a job would it be to move your HX, and put the boiler circ in there with it? Like, move the HX down, to close to the level of where the undergound comes in. And put the circ on the return side of the HX? Per Marshys earlier suggestion? At first, after seeing that pic, I was going to just suggest moving the circ there, to right before where the return lines goes underground. Vertically. That being the lowest point between the HX and where it goes back underground. But it might not be easy to mount it right there. So if you also move the HX down to that level, you might create a piece of solid horizontal piping you could mount the circ into more easily. And you would get everything below your boiler water level. Said without knowing exactly the height difference between your HX & boiler water level. But I think getting the circ where the water is coolest (after the HX) will do the most for the cavitation issues in your situation of wanting the most heat to storage you can get & not having much leeway in increasing your circ inlet pressure.
> 
> Not sure I said all that the right way, but hopefully with everything everybody is throwing at you, you can find a tidbit or two to help.


My hesitation for that suggestion is you end up with 20' of pipe in the suction side that is 1" and the restriction of the htx.

@warno, what's the elevation difference between the lowest point you can mount the pump in the boiler cabinet vs the lowest point you can mount it in the house plumbing room?

 If it was moved to the plumbing closet in the house it might make the most sense to put the pump on the floor where the pex comes up through the floor. Again, you still have the restriction of 20' of 1" pex which may or may not be beneficial depending on the elevation difference. 

It may work it might not, might be worse idk. I'd start with the easiest thing and try moving it lower in the boiler cabinet first so he doesn't have to rerun the electrical.


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## maple1 (Jan 13, 2018)

Just also kind of realized there is also a catch-22 in the talk of raising the height of the boiler water, and expansion tank adding. That would also likely raise the height of your hottest boiler water, further away from your circ inlet. May be good for cavitation but not the end goal of hottest to storage. Depending on mixing factors within the boiler.


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## warno (Jan 13, 2018)

My boiler shed and the garage floor are basically on the same level. So I  think with what has been discussed here it wouldn't matter a whole lot if I put the circ at floor level in the boiler shed or in the garage with the other plumbing. Since it would be basically the same distance from top of the water level. 

I think the easiest thing I could do is replumb the suction side with bigger piping and move the circ to the floor level in a horizontal position.


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## Marshy (Jan 13, 2018)

warno said:


> My boiler shed and the garage floor are basically on the same level. So I  think with what has been discussed here it wouldn't matter a whole lot if I put the circ at floor level in the boiler shed or in the garage with the other plumbing. Since it would be basically the same distance from top of the water level.
> 
> I think the easiest thing I could do is replumb the suction side with bigger piping and move the circ to the floor level in a horizontal position.


Yes. 
I'll double check my text on pump speed vs NPSH. From memory, lower speed should lower NPSH and mitigate cavitation. If you don't need as much flow a smaller pump or 3 speed pump would help you. I'll double check though and confirm.


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## warno (Jan 13, 2018)

Watching a fire burn right now. 

Reading right on the pipe going into the pump is 199°F. With the pump on speed 2, I get cavitation. With the pump on speed 1, there's nothing. 

I'm reading a 25° delta T at my plate HX on the boiler side. 

The pump is a bell and gossett NRF-36. 

Should I still go through with the replumbing in the boiler shed or just run on speed 1?


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## Marshy (Jan 13, 2018)

warno said:


> Watching a fire burn right now.
> 
> Reading right on the pipe going into the pump is 199°F. With the pump on speed 2, I get cavitation. With the pump on speed 1, there's nothing.
> 
> ...


I thought you said it was a single speed. My bad, I'd recommend running it on low and not messing with the plumbing at all. Any reason you would need the higher flow?

Let me see if I understand this. You have a 25F delta from boiler outlet (199F) compared to the cold side outlet of the htx? Or was thst measured at the return pex in the boiler cabinet? 

What's the temp drop from boiler outlet to htx inlet (ie loss between boiler to htx)? 
What's the temp drop from the cold side of the htx to the return in the boiler cabinet? 

Pick your poison I guess, running on low speed or on medium and throttle the discharge slightly if you need a little more flow. Even throttled on medium it's probably more flow than slow speed unthrottled.


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## maple1 (Jan 13, 2018)

I am thinking the only down falls to running the boiler circ slower would be increased boiler idling, or not getting enough btus to the house to keep up with demand.


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## warno (Jan 13, 2018)

Marshy said:


> I thought you said it was a single speed. My bad, I'd recommend running it on low and not messing with the plumbing at all. Any reason you would need the higher flow?
> 
> Let me see if I understand this. You have a 25F delta from boiler outlet (199F) compared to the cold side outlet of the htx? Or was thst measured at the return pex in the boiler cabinet?
> 
> ...



Yeah the bell and gossett NRF-36 is a 3 speed pump. 

From boiler outlet to HX inlet there is less than 1° loss. So at 199° boiler the HX is getting ~199°. The 25° delta was on the HX only. So the inlet of the HX was 199 and outlet was 174. Then boiler return is just a few degrees less then that. 

It took alot of throttling of the discharge valve to get the cavitation to stop. But switching to lower speed it was instant. The reasoning i want to run a higher speed is for more flow through the HX.



maple1 said:


> I am thinking the only down falls to running the boiler circ slower would be increased boiler idling, or not getting enough btus to the house to keep up with demand.



My boiler only flows to the plate HX in the garage which charges storage. It doesn't go to the house. All heat loads are pulled from storage. So the only load I need to worry about with the boiler is storage charging.


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## Marshy (Jan 13, 2018)

warno said:


> Yeah the bell and gossett NRF-36 is a 3 speed pump.
> 
> From boiler outlet to HX inlet there is less than 1° loss. So at 199° boiler the HX is getting ~199°. The 25° delta was on the HX only. So the inlet of the HX was 199 and outlet was 174. Then boiler return is just a few degrees less then that.
> 
> ...


Got ya. What about the other side of the htx, what is the temp delta? 

You can still try previously discussed in an effort to get it to run on medium speed. Hope it works out for you. Keep us up to date.


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## warno (Jan 13, 2018)

Marshy said:


> Got ya. What about the other side of the htx, what is the temp delta?
> 
> You can still try previously discussed in an effort to get it to run on medium speed. Hope it works out for you. Keep us up to date.



The storage picks up about 20 degrees to the boiler loss of 25. 

I'll go for broke and increase supply piping size and lower boiler pump to the floor like discussed above. It'll have to wait a few months because I'll have to drain the boiler water down below that level to get the welding done.


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## maple1 (Jan 14, 2018)

I think then that with a 20dT to storage, and not hearing of any boiler idling increasing, you should be good to go running on the slower speed. Also sounds like your boiler dT is a bit more than 20 - actually closer to 30. I'm not sure you could improve things very much in all that, really. I think I would be happy to leave things just as they are.


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## Marshy (Jan 14, 2018)

If he's looking to increase the delta T on the storage side he could slow that pump down and it should pick up more heat I believe. 

@warno, what are the actual temps on the storage side of the htx in and out?


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## warno (Jan 14, 2018)

Here's is a boiler log a did the other day. You can see the delta T temps for both sides of the HX.


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## warno (Jan 14, 2018)

Well @maple1 Is correct. I tried a burn tonight with the boiler pump on speed 1 and it is idling way more then it ever has. The delta T looks good at the HX but the BTUs are not getting out of the boiler fast enough. The difference between the delta T on speed 1 vs 2 is only a few degrees so if I can remain burning and not idling then I need to run at least speed 2. 

So with that knowledge, I'm back to relocating my pump to the floor and plumbing in larger supply to it.


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## Marshy (Jan 14, 2018)

@warno, what is the htx rating?


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## maple1 (Jan 14, 2018)

warno said:


> Well @maple1 Is correct. I tried a burn tonight with the boiler pump on speed 1 and it is idling way more then it ever has. The delta T looks good at the HX but the BTUs are not getting out of the boiler fast enough. The difference between the delta T on speed 1 vs 2 is only a few degrees so if I can remain burning and not idling then I need to run at least speed 2.
> 
> So with that knowledge, I'm back to relocating my pump to the floor and plumbing in larger supply to it.



I wish I wasn't. If that helps any.


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## warno (Jan 14, 2018)

Marshy said:


> @warno, what is the htx rating?



This is my HX



maple1 said:


> I wish I wasn't. If that helps any.



It's ok. I'm good with changing things up. Like i said the plumbing pieces aren't much money for me and the welding and fitting is my pass time anyway.


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## maple1 (Jan 14, 2018)

That's not a very big hx. Marshy might be on to something.


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## warno (Jan 14, 2018)

maple1 said:


> That's not a very big hx. Marshy might be on to something.



I'm thinking I'm going to buy a 30 plate.


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## maple1 (Jan 14, 2018)

I would likely go even bigger.


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## warno (Jan 14, 2018)

maple1 said:


> I would likely go even bigger.



I'm running at about 20ft of head at about 10 gpm with the current setup on the boiler side. My boiler can more then keep up with the delta T at this rate. And if I can get it to burn better with next years modifications it should keep up even better yet. How big of a HX would you recommend? Keep in mind i have 22 ft of underground piping to the HX that is only 1" pex.


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## Marshy (Jan 15, 2018)

I'm not versed is sizing htx's for boiler systems but I believe the temp deltas you have shown us is indicating the htx is way too small. A 20-25 delta T is about half of what you should be reasonably shooting for. Maybe another member can help with that aspect. I saw some good comments from @Karl_northwind in another thread.


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## maple1 (Jan 15, 2018)

I'm also a bit over my head if I try to size your HX. I have one, same size as yours actually, doing just my DHW. But I just used seat of the pants to pick it, based simply on what I read others posting about on here. It works great for me, but I only use it for my DHW. Which is maybe 1/30 of my heating load. I can't remember what I see for dTs, but I have very slow flows going through it.

I don't think I would go less than a 40. Then from memory budget might kick in, I think they can get kind of expensive. But bigger would be better - the bigger it is, the more ability to get the heat from your boiler to your storage. 

Now, to throw a couple more curve balls at you, I had a couple more thoughts come to me as I was trying to drag my butt out of bed a while ago.

How is your return temp protection mixing valve doing? Have you been watching the temps of return water entering the boiler? If it is letting more bypass flow through than it needs to, or still letting some in when it shouldn't be - that would also likely contribute to some increased idling.

And I notice in your chart that you kept both circs on the same speed. Have you tried boiler circ on speed 1 & storage circ on speed 2? If you already mentioned that, I either missed it or forgot.

Would really like to see more from others on the HX sizing aspect.


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## hondaracer2oo4 (Jan 15, 2018)

http://flatplateselect.com/site/pub/login.aspx?ReturnUrl=/site/default.aspx

You will need to create a account but it is free. Allows you to input different flows and deltas and see what you get.


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## Marshy (Jan 15, 2018)

@maple1 is right. I would absolutely run the storage side pump on speed 2 and run the boiler side on 1 for the time being. That might help you maximize the heat transfer.

Thanks for the link @hondaracer2oo4, I'm playing with it now.


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## Karl_northwind (Jan 15, 2018)

If you are using the flatplate select software, know that all 5x12x30 plate HX's (for example) are not created equal.  make sure you compare the actual square footage of the HX with whatever you are using if you don't use the AIC flatplate HX.  If I remember correctly I have a 30 plate 5x12 from one premium manufacturer that has 13 square feet of transfer area, and another cheapo chinese that has 8 square feet. YMMV


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## hondaracer2oo4 (Jan 15, 2018)

What size is your flat plate? Is it a 20? If so that’s tiny. Use the calculator I posted to play around but there is no draw back to oversizing your plates other then cost and you can get some cheap plates. I have a 50 plate which is feeding my primary loop on my hydro air system. No problems with the plate after 3 years. I would run a 70-100 plate hx if I was heating a water store. You can Always throttle your owb pump or tank pump to dial in th delta thst you aim for.


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## Bob Rohr (Jan 15, 2018)

Any way to put some coils inside the boiler, and internal HX that could be pressurized would solve all the issues.

Keep in mind at high operating temperatures you may cavitate in the piping above the water level in the boiler.  Cavitation is not limited to the volute of a pump.  Anything or place where you drop below atmospheric pressure, especial;lc at high operating pressures can cause cavitation.  You can hear cavitation in a garden hose when you kink it off!  Any restriction in the piping that causes that pressure reduction can set up cavitation.

Is that fan coil above the water level?  Here is the match and explanation for cavitation in open systems.


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## Marshy (Jan 15, 2018)

Karl_northwind said:


> If you are using the flatplate select software, know that all 5x12x30 plate HX's (for example) are not created equal.  make sure you compare the actual square footage of the HX with whatever you are using if you don't use the AIC flatplate HX.  If I remember correctly I have a 30 plate 5x12 from one premium manufacturer that has 13 square feet of transfer area, and another cheapo chinese that has 8 square feet. YMMV


The e bay ad he provides doesn't disclose any useful information to be able to determine it's performance. It only says it's a 20 plate htx with plate dimensions of 20"x4.24".

If I used the software correctly, a more appropriate size htx would be a 30 plate 10"x20" htx.

I assumed boiler supply temp to htx 185F, and outlet from htx 140F at 10gpm. On the storage side of htx, inlet 135F and outlet of 170F.

That being said, I'm making more than a few assumptions. First I'm assuming a larger delta T than he listed in his excel sheet 185-140 on the boiler side, and 135-170 on the storage side. I'm also assuming a flow rate of 10gpm from the boiler pump because the pumps maximum flow on speed 1 is ~26gpm unrestricted.

This probably doesn't add a whole lot of value other than big picture concept that I believe @warno needs a larger htx.









Here is the htx he has.


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## Bob Rohr (Jan 15, 2018)

Water inside the evac tube solar collectors boils at around 100- 110 due to the vacuum in the tube.

o


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## warno (Jan 15, 2018)

Ok this thread was added to alot since last i checked I'll try to get everything answered. 

@maple1 my protection is doing it's job well anything over 145° the bypass side is completely shut. The bypass tube goes "cold" while burning. And i have tried many different circ speed combos. It seemed the same speed on each yielded best results. Currently I've switched boiler back to speed 2 and storage is on speed 3. 

@hondaracer2oo4 I have set up an account on flat plate.  That's where i sized my current HX. but not having a good idea of my flows and boiler output i was guessing, at best, at many of the numbers. The HX i settled on is the exact one from that eBay ad. It's a 20 plate at those deminions. 

@Bob Rohr There's not really a good way to put coils in my boiler. Given the internal construction and internal flue HX there's a bunch of things in the way and doesn't leave alot of easy working room in there. 

@Marshy my biggest concern with a much larger HX is 1) cost and 2) if boiler return temps drop below 145 then the mixing valve will be bypassing pretty often. Which i know is it's job, but if i can send 150° water back to the boiler I'd be alot happier.


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## Marshy (Jan 15, 2018)

warno said:


> Ok this thread was added to alot since last i checked I'll try to get everything answered.
> 
> @maple1 my protection is doing it's job well anything over 145° the bypass side is completely shut. The bypass tube goes "cold" while burning. And i have tried many different circ speed combos. It seemed the same speed on each yielded best results. Currently I've switched boiler back to speed 2 and storage is on speed 3.
> 
> ...


You could buy another htx and plumb it in series instead of buying a larger one to replace it with.

I'd suggest you do this in phases. Get the inlet piping converted to 1.5" and see if you can run the pump on speed 2 without cavitating. If you think you need more heat get a second htx and plumb it in series. Let the diverter valve do it's job. To my understanding that valve is not open/shut it throttles.  In the end, BTU's are going into the storage regardless if the water temp coming back.  Feel free to correct me if that is bad thinking.


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## warno (Jan 15, 2018)

@Marshy the thermomix valve does throttle the bypass flow, yes. But it makes some pretty bad sounds when it's at that butter zone of open vs shut on the bypass side. Thats why I just assume it keep the bypass side shut.


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## maple1 (Jan 15, 2018)

Marshy said:


> You could buy another htx and plumb it in series instead of buying a larger one to replace it with.
> 
> I'd suggest you do this in phases. Get the inlet piping converted to 1.5" and see if you can run the pump on speed 2 without cavitating. If you think you need more heat get a second htx and plumb it in series. Let the diverter valve do it's job. To my understanding that valve is not open/shut it throttles.  In the end, BTU's are going into the storage regardless if the water temp coming back.  Feel free to correct me if that is bad thinking.



That sounds sound.

I started out with a sidearm on my DHW. When I realized it wasn't getting the job done I was looking for, I added the FP in series. I also swapped my storage side 3 speed 15-58 for an Alpha, and added a B&G variable speed Ecocric on the DHW side, so I have pretty well complete variable control over flows on each side.

Warno may want to adjust the phases based on his priorities & preferences - if it is quite quick & easy for him to add a FP (vs. doing a long shut down & reman on his boiler outlet), that might be first. Or if he can or can't wait until the heating season is over.


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## warno (Jan 15, 2018)

maple1 said:


> That sounds sound.
> 
> I started out with a sidearm on my DHW. When I realized it wasn't getting the job done I was looking for, I added the FP in series. I also swapped my storage side 3 speed 15-58 for an Alpha, and added a B&G variable speed Ecocric on the DHW side, so I have pretty well complete variable control over flows on each side.
> 
> Warno may want to adjust the phases based on his priorities & preferences - if it is quite quick & easy for him to add a FP (vs. doing a long shut down & reman on his boiler outlet), that might be first. Or if he can or can't wait until the heating season is over.



I can wait until this season is done. That's my plan anyway.

Can a flatplate HX be ran in series with another FPHX, Like marshy said?  I've never seen it done but if i can get a 30 plate and run it with my 20 I'll do that.


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## Marshy (Jan 15, 2018)

warno said:


> I can wait until this season is done. That's my plan anyway.
> 
> Can a flatplate HX be ran in series with another FPHX, Like marshy said?  I've never seen it done but if i can get a 30 plate and run it with my 20 I'll do that.


I know your looking for someone else's concurrence but I'll just add that the only potential down side is removing too much heat from your boiler side. Maybe you can play with pump speeds to add another level of control or pipe in a small bypass on the boiler side of one of the htx's..?

You will need to plumb both sides of the htx's in series obviously.


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## warno (Jan 15, 2018)

I'm not saying your wrong @Marshy, I'm sure it's been done. I've just never seen it. And I'm defiantly not ruling it out. It would just take some fancy plumbing working to achieve.


Here's a 50 plate for just under $200. Is this more what we're talking about to get by with one HX?


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## Bob Rohr (Jan 15, 2018)

hondaracer2oo4 said:


> What size is your flat plate? Is it a 20? If so that’s tiny. Use the calculator I posted to play around but there is no draw back to oversizing your plates other then cost and you can get some cheap plates. I have a 50 plate which is feeding my primary loop on my hydro air system. No problems with the plate after 3 years. I would run a 70-100 plate hx if I was heating a water store. You can Always throttle your owb pump or tank pump to dial in th delta thst you aim for.



You will start losing some efficiency if you oversize a plate HX by too much.  What happens is the channel velocity drops, you lose turbulent conditions and heat exchange diminishes.  I suppose that is why they make so many sizes and have the software to select very close to what you need.

The one question still not answered is what BTU output is the boiler capable of.  If you want it to run to it's best potential, the pumps, pipes, HX, etc needs to be sized to the load it needs to move.  Wood boilers tend to be most efficient running full out, in gasification mode.  Or completely shut off 

With homemade stuff there is usually a trial and error period to dial it in.


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## warno (Jan 15, 2018)

@Bob Rohr I can't tell you exactly ther output of my boiler. Best I can do is post my burn log I did a few weeks back. I can't see investing in a btu meter to only use it once or twice. 








I do batch burns in my boiler and I'm getting some secondary flame but it's not as much as I'd like. Next year I'm going to change a bunch of things and aim for getting sustained secondary.


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## Bob Rohr (Jan 15, 2018)

Like Karl mentioned, look at the sq ft of the HX not just the plates.  That 50 plate looks like .417X 50= 20 sq ft surface.

The 10X20- 30 plate shown in an earlier post is 36 sq ft.  Plus it has 1-1/2 connections and very low pressure drop even at 220,000 BTU/hr.

With the 10X20-30 and the low pressure drop, maybe go with a flat curve circ to help lessen or eliminate cavitation.  Those high head, NRF- 36 high rpm circs are very prone to cavitation, and your high operating temperatures increase that potential.

If the circuit is just the boiler and HX you want a high flow, low head circulator.  This Taco graph shows the differences between low and high head, the 0010 for example moves about the same gpm as a 0013, but much less head.

Taco used to build a cicc specifically for OWF, even showed the NPSH.  It was an open frame motor so the issues of gunning up a wet rotor style circ were eliminated.


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## warno (Jan 16, 2018)

So I was playing around with the numbers on the flatplate website. I came up with a HX that I think I find on eBay for around $200. I don't have alot of money to drop on a big name brand or custom HX. That's why I'm trying to find one I can pick up on eBay. But anyway here's one I found.








It's showing 30° delta Ts on both sides @ 10gpm. I'm guessing that that 30°delta isn't always the case of the water temps get lower. Is this correct thinking? If so what can I expect to see if I'm running 170 boiler water into the HX?


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## maple1 (Jan 16, 2018)

I got my B&G FP thru my local supplier for no more than I was seeing them online for.

Not sure on your local supplier situation. Mine had to order it.

Then again getting stuff online here is usually not an advantage by the time you pay for shipping & usually a currency exchange & customs etc...


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## warno (Jan 16, 2018)

maple1 said:


> I got my B&G FP thru my local supplier for no more than I was seeing them online for.
> 
> Not sure on your local supplier situation. Mine had to order it.
> 
> Then again getting stuff online here is usually not an advantage by the time you pay for shipping & usually a currency exchange & customs etc...



It's not too bad getting stuff online in the states. 

Here's the one I'm looking at.


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## Bob Rohr (Jan 16, 2018)

Better.  With the inputs you used that HX will transfer 145,991 BTU/hr.  I suspect your boiler is capable of more than that, so you may need to watch how you fire it or you may still see some cycling, short run times or excessive idling.

Also you input 10 gpm on the boiler side I'd guess the circ pump, NRF 36, you are currently using is pumping more than twice that flow rate?  If so the delta will decrease.  Try putting 20 gpm in the A side calculation to see what happens.

If you want to pump 10- 15 gpm, which matches the HX output simulation,  consider a Taco 007, a flat curve low head circulator.  That would probably eliminate cavitation concerns compared to the high head NRF.

I wonder that bargain priced HX are built equal to quality name products.  The weight, square footage, grade of SS, plate thickness and assembly methods are probably the big difference.  Usually if it is an import knock-off they have cheapened it somehow.


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## Marshy (Jan 16, 2018)

Bob Rohr said:


> Better.  With the inputs you used that HX will transfer 145,991 BTU/hr.  I suspect your boiler is capable of more than that, so you may need to watch how you fire it or you may still see some cycling, short run times or excessive idling.
> 
> Also you input 10 gpm on the boiler side I'd guess the circ pump, NRF 36, you are currently using is pumping more than twice that flow rate?  If so the delta will decrease.  Try putting 20 gpm in the A side calculation to see what happens.
> 
> ...


Here's the curve for his pump. 




You make good points.


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## warno (Jan 16, 2018)

@Bob Rohr i was just going to post what marshy did. 

My current boiler side system is about 20ft of head. So if I'm reading that curve rightn it should be close to 10gpm. 

And I'm sure you are right about the off brand HX efficiency. Maybe I'll step it up to a 50 plate from eBay and if need be throttle the gpm at the boiler.


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## Marshy (Jan 16, 2018)

warno said:


> @Bob Rohr i was just going to post what marshy did.
> 
> My current boiler side system is about 20ft of head. So if I'm reading that curve rightn it should be close to 10gpm.
> 
> And I'm sure you are right about the off brand HX efficiency. Maybe I'll step it up to a 50 plate from eBay and if need be throttle the gpm at the boiler.


Sorry,  I was going to correct you earlier when you started you thought you had 20' of head.  Correct me if I'm wrong but, I believe you came up with that value because that's the distance between pump and htx right?

If so, that is not the correct. The best way to determine the pumps discharge head is to measure the discharge pressure before it returns into the boiler. Convert that pressure to ft of water column and find where that pressure intersects the operating curve on the graph.  That will tell you how much flow its pumping.

The analytical method of figuring that out is more complicated.  For every linear for of 1" pex you will have "x" feet of head loss (pressure loss expressed in units of feet of water column). You would total all the head losses in the system and subtract them from the pumps maximum discharge head and find thast point on the curve to determine flow.


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## warno (Jan 16, 2018)

@Marshy I figured just under 20 ft of head for that pump with the help of another member here. We went through each fitting and gave it a length of pipe, in feet, based on online calculators for such information. So that 20 feet includes every fitting and pipe length from the boiler supply to return. We added alittle extra for any forgotten factor.


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## TCaldwell (Jan 16, 2018)

I think it was jebatty?


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## warno (Jan 16, 2018)

Yep that was who it was.


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## Bob Rohr (Jan 16, 2018)

Basically adding all the feet of pipe and fittings gives you an equivalent length number.  A few other steps are needed.  

If the boiler loop side is just the wide open boiler and HX you mentioned above 10 gpm? I don't see more that a few, maybe 5' of heat?  The HX spec shows the pressure drop at the flows you entered 1.1'?  

Is the boiler piping undersized?  1" would be fine. 1-1/4 better if you try and move more than 12 gpm or so.

Maybe Jim was calculating the underground loop, Hx and B side?


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## Bob Rohr (Jan 16, 2018)

This issue will take you through the steps to determine the pressure drop of the various circuits.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf


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## warno (Jan 16, 2018)

Bob Rohr said:


> Basically adding all the feet of pipe and fittings gives you an equivalent length number.  A few other steps are needed.
> 
> If the boiler loop side is just the wide open boiler and HX you mentioned above 10 gpm? I don't see more that a few, maybe 5' of heat?  The HX spec shows the pressure drop at the flows you entered 1.1'?
> 
> ...




The boiler loop runs underground into my garage. Here's pictures of everything. The boiler runs underground 22 feet of 1" thermopex  into the garage then into a diverter valve - HX - and return. Everything is 1" plumbing. I know everything is messy. It's been a season of trails and errors.


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## Bob Rohr (Jan 17, 2018)

Sorry, I thought the HX was at the boiler location.  With this pic I can see the 20' head being realistic.

Another thought, I have seen some boilers with tube heat exchangers welded to the outside.  Many of the old wood stoves had coil kits that could attach externally.

Some or the Euro boilers have a external HX like that connected to city water as the over-heat protection.  If the boiler gets too hot water flows and dumps through that welded on HX.


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## warno (Jan 17, 2018)

Bob Rohr said:


> Sorry, I thought the HX was at the boiler location.  With this pic I can see the 20' head being realistic.
> 
> Another thought, I have seen some boilers with tube heat exchangers welded to the outside.  Many of the old wood stoves had coil kits that could attach externally.
> 
> Some or the Euro boilers have a external HX like that connected to city water as the over-heat protection.  If the boiler gets too hot water flows and dumps through that welded on HX.




Any excess heat from my boiler will be dumped in the garage via dump zone water/air HX. My main concern is getting my storage up closer to 190 because my heat emitters are water to air HX built in to my duct work. And although I'm only heating the garage at the moment I've learned that anything much under 140 it takes a long time to satisfy the thermostat.


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## Bob Rohr (Jan 17, 2018)

Those last 10- 20 degrees over 170 are the toughest to get exchanged, as you are learning   This is true with closed loop also.  As the delta T shrinks the exchange slows.
It is doable, but with the deck stacked against you like that it will be harder to accomplish. The conditions you are working with, high head circulator, open system, large pressure drop circuit are adding up, working against you.

Temperature and pressure, those are the two factors involved in the cavitation issues I suspect you are experienced.  Change one or both and you chances for success go up.

With an open system the PONPC, point of no pressure change is at the actual water level, so pumping into the boiler is not a viable solution, pumping away adds the circulator ∆P to the circuit, which you dearly need.


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## maple1 (Jan 17, 2018)

This has been a very interesting thread - Catch-22's all over the place.


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## Marshy (Jan 17, 2018)

The 20' of head loss you came up with seems high to me.

1" pex has a pressure loss of 11.4 psi per 100 ft, or 1.14 psi per 10 ft at 15 gpm. If you convert that to feet of head, 1.14 x 2.3 = 2.622 ft of head loss for 10' of pex. So you have about 10.5' of head loss in 40' of pex if you pumping 15 gpm, and less loss as flow goes down.

Actually, 0.55 psi head loss at 10 gpm. 0.55 x 2.3 = 1.265' per 10', or  5.06' for 40' of pex.

What head loss are you assuming for the htx?

 I see four 45 elbows on the copper side and a zone valve. I also see a strainer at the pump discharge and a 90 elbow.  Then returning into to the boiler you have a 45, the diverter valve and a 90 into the boiler jacket. Maybe 20' is reasonable?

One thing you absolutely cannot have is a pump with a discharge head less than the system resistance (head loss). You won't move any water.


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## warno (Jan 17, 2018)

@Marshy here's a list of every fitting in my boiler loop.  

BV = full port ball valve. 
Everything is 1" unless otherwise noted
The diverter has a CV of 7.5
The themomix has a CV of 10
A similar FPHX on the site has a pressure drop off 2.7PSI on boiler side.


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## warno (Jan 17, 2018)

I'm looking for a new FPHX and I'm wondering if there is a noticeable difference between 1" port and 1.25" ports? If I go with 1" MPT ports I can reuse my exsisting parts.


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## Bob Rohr (Jan 18, 2018)

If the boiler connections are 1" and piping are 1" that will be one of the limits on how many BTUs you will get out of the beast.

What about combining the boiler connections with reverse return, upsize to 1-1/4"  and feed directly to the HX in the boiler room.  That gives you the best chance of getting full output, at least to the HX,  and could probably run with a smaller, flat curve circulator.  So the cavitation issue goes away.

Yes you may still need the large pump to overcome the small tube and pressure drop into the building, if in fact you want 12- 15 gpm.

I'd abandon the 190° target SWT at the heat emitters.  180 should be plenty for any hydronic AH, fin tube, etc. even 160.  That would also eliminate trying to drive the boiler so high and always be at that fine line of boiling over.  Probably get away from any dump zone if you don't drive it so hot.

Really the only reason to run that 190 would be to store in a buffer and pull off it down to say 100 for radiant or low temperature emitters, then you have a huge 90∆ to work with.

The trend in the industry is to design hydronic systems to cover the load on design days with no more than 120F!  That is a commonly used design temperature  in Europe with radiant floors, ceiling and walls or generously sized panel rads.  With a properly sized coil an AH could run down around 140 SWT.

Piping losses of course go down with lower operating temperatures also, and wood consumption.

Lets say your wood to water efficiency is 70%.  The higher the operating temperature the greater all the losses and efficiency hits, all along the line.

Heat loss and heat transfer is all about ∆T.  The greater the delta, the higher the heat exchange, including loss from the boiler jacket, piping, HX, underground, etc.


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## warno (Jan 18, 2018)

@Bob Rohr The one and only problem with putting the HX in the boiler shed is excess heat dump. With running the boiler lines into the garage first then I can dump any over heat situation into a building that I actually want heated. I know the dump zone won't run all the time or with every burn, but if I do get into a over fire situation I'd rather use that heat to my advantage. I had actually thought about that during this discussion in this thread. 


I just a had thought and I want to ask a question before presenting my thought. 

My cavitation issue on my boiler pump is because I have a high head loss number on the discharge side vs a low pressure number on the suction side, is this correct?


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## Marshy (Jan 18, 2018)

warno said:


> ...
> My cavitation issue on my boiler pump is because I have a high head loss number on the discharge side vs a low pressure number on the suction side, is this correct?


No, your cavitation issue is strictly related to the pressure and temperature of the fluid entering the pump. It has little to do with the head loss on the discharge side of the pump. You either need lower temp water entering the pump or higher pressure. Only way to increase pressure is to lower the pump in relation to the water level in the boiler jacket. You can also reduce the head loss in the suction piping but you have so little to begin with its unlikely to make a difference. You also have so little extra room to lower the pump it may not cure it either. That is why lowering the water temp may be the ultimate cure. That or try a low head circ pump because it does not need as high a pressure at the inlet of the pump (required NPSH) which means you can run a hotter water temp. Clear as mud? 

Just for clarity, the system restrictions on the discharge (head losses) do affect where the pump operates on its performance curve. Depending on the pumps characteristics the required NPSH curve could be fairly flat, however the NPSH required usually increases as the discharge flow from the pump goes up. Therefore, adding restriction to the pump discharge lowers the potential for cavitation, albeit minor. 

This picture is an example of the pumps operating curve and NPSH required. It also shows the system resistance curve. If you add more resistance the pump puts out less flow and more pressure, you move back (left) on the operating curve. The NPSH required for that operating point can be determined by drawing a straight line down to the NPSH curve. If the curve is flat adding restriction does very little good.


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## warno (Jan 18, 2018)

Well my thought was plumbing in this configuration. The first circ coming off the boiler would be as low to the ground as possible and all suction side piping would be 1.5".  







But now that you say the head loss isn't that important I don't think this would matter. My thought was the first circ would add pressure to the circ pumping into the garage. But with what you just said it makes me think the first circ, in this configuration,  would cavitate just the same.


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## Bob Rohr (Jan 18, 2018)

Here are some formulas to show how and when cavitation is possible.  I think you have 1" piping so that factor in the example is correct, not sure about you exact flow rate, assume one and try a few others.

It sounds like you have already seen or heard cavitation when you change pump speeds so you need to make some changes.

Several options have been presented, if you run the math it will predict which will or won't work.

I hate to see you change piping and locations if they will not solve your issues.

I'd be glad to send you a Quicksetter so you can observe some actual flow rates if that helps.  Just know a 1" Quicksetter only goes to 10 gpm.  Installing an 1-1/4 on 1" piping doesn't make a lot of sense as your piping is undersized for  the higher flow rates, that is why I suggested combining the two 1" boiler connections so you have the ability to handle the flow rates I think you are trying to target.


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## jwise87 (Jan 18, 2018)

Bob Rohr said:


> Here are some formulas to show how and when cavitation is possible.  I think you have 1" piping so that factor in the example is correct, not sure about you exact flow rate, assume one and try a few others.
> 
> It sounds like you have already seen or heard cavitation when you change pump speeds so you need to make some changes.
> 
> ...




A down and dirty way he could check flow would be to pull the return off at the boiler and dump into a bucket. Obviously not at operating temps. That would give an idea of the flow to punch into the formulas.


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## warno (Jan 18, 2018)

@Bob Rohr I'm a little confused by when you say adding 1 1/4 to 1" piping?  And by pulling from both 1" connections do you mean pull from both my supply ports and return into both my return ports?


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## Marshy (Jan 18, 2018)

warno said:


> @Bob Rohr I'm a little confused by when you say adding 1 1/4 to 1" piping?  And by pulling from both 1" connections do you mean pull from both my supply ports and return into both my return ports?


I think he was saying to connect the lower boiler port to the suction of the pump (combine the upper and lower) in an effort to reduce head loss on that side of the pump. That's how I understood it.

While it would reduce some head loss, my only hesitation about that is if you still have 1" pipe from where the two tee together up to the suction of the pump you haven't taken full advantage of eliminating the restriction. Converging flow in a tee is fairly restrictive and if you are still using 1" after that tee I don't think its worth the effort. That is why I suggest just going with 1.5" pipe on the whole suction side. On second though, you could connect both ports together as suggested but use 1.5" pipe. I would add full port ball valves to each port and run it just drawing from the upper port. If its cavitating open the lower port and see if it goes away. Also try just the lower port as the colder temp would also be beneficial. Use a long sweep elbow where ever you can on the suction side.  (I feel like that was a small tangent, sorry.)

Will either option solve the problem? I don't know without making some calculations (and assumptions since we don't know the flow rate). Good advice was given about how to determine the flow. If you get the chance try to use the 5 gal bucket method and estimate flow. 

I could attempt to run some numbers for you but I would need some dimensions from you. From the floor of the boiler cabinet what is the distance to the water level in the boiler jacket? Can you total up the straight copper tubing leading up to the HTX and also back to pex return?


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## Bob Rohr (Jan 18, 2018)

yes increase to 1-1/4" when you combine upper and lowers.  Think of it as building a manifold where a bunch of small ports enter into the larger trunk piping.  This allows you to flow more through the boiler and HX.  Install the HX in the building with the boiler.  With a properly sized HX you should be abl;e to get most all the energy out of the boiler and into the box (HX).


With a non gasification boiler I/ you might be tempted to remove the return mixing valve.  Rarely do OWF designs worry about return temperature, especially at elevated temperatures that you want to run.  Only on cold start up would you have some condensation.

Or put the return temperature protection on the B side.  We are trying to simplify the A side piping and pressure drop as much as possible.

Our goal is to get as much heat out of the boiler, reduce cavitation, and be able to still run high temperatures.  At least I think that is the goal? 

Pump performance could be measured by measuring pressure on inlet and outlet, refer to the pump curve.  pretty easy to get a few 1/4 gauge ports into the piping.  I've seen guys use the cheap saddle valves to get into a pipe for pressure readings if you want quick and simple.


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## Bob Rohr (Jan 18, 2018)

P/T ports aka pressure temperature.  These small fittings are often included throughout a piping system.  Officially they are named after the inventor Peterson.  They allow you to "needle in" a gauge to read pressure or temperature.  Mechanical engineers use them often on systems to check performance and trouble shoot.

Think of a basket ball inflation connection, that is how PT ports work.  Spit on the needle and slide it in.  Available all the way down to 1/8 connection side, easily tapped into piping after the fact.  Larger pumps often have threaded openings to add PT ports.


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## warno (Jan 18, 2018)

@Bob Rohr or @Marshy I'm trying to do that math what would I enter for my psi entering the circ since its an open system? Wouldn't that be the weight of the water pushing down? If so, isn't that the .435 psi/ft we all talked about earlier?


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## warno (Jan 18, 2018)

based on 10 gpm and 190° water are these my numbers?


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## Marshy (Jan 18, 2018)

warno said:


> @Bob Rohr or @Marshy I'm trying to do that math what would I enter for my psi entering the circ since its an open system? Wouldn't that be the weight of the water pushing down? If so, isn't that the .435 psi/ft we all talked about earlier?


The short answer is yes, the long answer is no.

Long answer: No, the NPSH available is the pressure of the water column minus the head loss from the pipe and any fittings.

Check this NPSH calculator out.

Adjust values to accommodate you actual setup. I guessed the flow rate (10 gpm). All other parameters should not be a guess. The piping material is cast iron unlined.

http://inventory.powerzone.com/resources/npsh-calculator/:al=600:alu=Feet Above Sea Level:fs=1:sp=48:spu=Inches:fr=10:fru=GPM:vc=Water:ft=194 Deg~p F (90C):v=0~p000315555:vu=KGM-1S-1 / NSM-2:sg=0~p965:vp=10~p17:vpu=PSIl=2lu=Feetid=1idu=Inches:hzc=Cast-Iron - new unlined:hzfc=130:rh=0~p011811023622047244:rhu=Inches:rfvu=FT/Sec:rnu=PSI:fits=Elbow, 90° SR|1!Valve, Ball, Full Port|1!


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## Marshy (Jan 18, 2018)

Here is another good reference for manual calculations.
https://www.engineeringtoolbox.com/npsh-net-positive-suction-head-d_634.html


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## warno (Jan 18, 2018)

Here's what i came up with for cast iron 1" @ 10gpm. Is this right?  Good or bad?


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## Marshy (Jan 18, 2018)

warno said:


> View attachment 221037
> 
> 
> Here's what i came up with for cast iron 1" @ 10gpm. Is this right?  Good or bad?


A negative NPSHA would mean its cavitating before it makes it to the pump lol. You must of mess something up. If you could post pics of the rest of the inputs I will help you.

Piping system section is for the section leading up to the pump only.


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## warno (Jan 18, 2018)

Marshy said:


> Piping system section is for the section leading up to the pump only.



Well this might help a bunch. Lol let me run it again.


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## warno (Jan 18, 2018)

here it is again @Marshy


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## Marshy (Jan 18, 2018)

warno said:


> here it is again @Marshy
> 
> View attachment 221041
> 
> ...


You still have one possible mistake that I can see. If you measured from the centerline of your pump to the top of the water level in the boiler jacket, is it only 9 inches in distance?


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## Marshy (Jan 18, 2018)

@warno, to also have four 45 elbows, not two. Don't forget about the two you used to make the turn out of the boiler jacket.


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## warno (Jan 18, 2018)

Marshy said:


> @warno, to also have four 45 elbows, not two. Don't forget about the two you used to make the turn out of the boiler jacket.



Oh yeah. Changed it here.


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## Marshy (Jan 18, 2018)

Now, check how much the NPSH increases if you moved the pump to the floor. Go back and add the distance to "Tank fluid level above or below centerline of pump". You will have to add additional length of pipe as well, possibly an elbow? You could take the opportunity to increase the pipe size as well.


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## warno (Jan 18, 2018)

@Marshy and here is with length added and pipe size increase. I thought it was posted in this thread but i can't find it, does anyone know the NPSH for the NRF-36 I'm running. I checked the manuals that supplyhouse.com offers but couldn't find it. Unless i over looked it.


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## Marshy (Jan 18, 2018)

warno said:


> @Marshy and here is with length added and pipe size increase. I thought it was posted in this thread but i can't find it, does anyone know the NPSH for the NRF-36 I'm running. I checked the manuals that supplyhouse.com offers but couldn't find it. Unless i over looked it.
> 
> View attachment 221044
> 
> ...


I have looked through B&G tech manuals for this pump but no NPSH data was available. I would give their tech line a call and ask if they can provide it.


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## Bob Rohr (Jan 18, 2018)

Marshy, explain to me how 48" of water column give you those pressures?  I come up with 1.7 psi with  the pump 48" below the water level?


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## Bob Rohr (Jan 18, 2018)

On smaller circulators generally they provide a chart like this.  So at 190F you need 2.2 psi on this Grundfos.   I've see 4 psi on other brands and models at 190F, depends on the type of pump to some degree.

 I'm of the opinion a 4' volume of water above the circ is around 1.7 psi.  Hence the cavitation potential in your case.


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## warno (Jan 18, 2018)

@Marshy I  called a B&G rep and they told me the NPSH is so small they don't publish it anywhere. He did say that dropping the pump lower would help. I asked if the larger piping would help, he said it may or may not. And i asked if going horizontal with the pump to get about another foot of pipe before it, he suggested staying vertical for fear that elbow right before the pump might cause issues. 

As far as the NPSH is there any other manufacturers that publish that number? Maybe we could crodd reference with a similar pump. 

Also he said my impeller might be hurt from thus going on and to check and replace if it's bad. Because a bad impeller would defiantly help cavitation.


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## Marshy (Jan 18, 2018)

Bob Rohr said:


> On smaller circulators generally they provide a chart like this.  So at 190F you need 2.2 psi on this Grundfos.   I've see 4 psi on other brands and models at 190F, depends on the type of pump to some degree.
> 
> I'm of the opinion a 4' volume of water above the circ is around 1.7 psi.  Hence the cavitation potential in your case.


I guess I left my brain at home when I was look at the numbers. I have to agree with you. We are probably using the calculator wrong. I'll play with it or have to break down and do it manually (been a little while, would be good practice).

I put in 1' for the water level to CL of pump, 0.1" of pipe, and no fittings, 1" pipe with 0.1" length and 0.1 gpm and it still says NPSH is 4.96 psig lol


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## Marshy (Jan 18, 2018)

I'll have to revisit this later and do it on paper.


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## Bob Rohr (Jan 18, 2018)

Here is the explanation for static pressure calculation.

As we all suspect Warno is on that fine edge with his static and cavitation, he has about 1.7 psi, the pump would like 2.  Since he cannot change the pressure change the temperature is his only viable variable.


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## warno (Jan 18, 2018)

If I take a pressure reading on the suction side of the pump it would be vaccuum reading right? Or no? 

I have a port on my suction side i can put a gauge on if this information would help us figure this out. And there's another port i can take a reading at the return just before going into the boiler.


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## maple1 (Jan 18, 2018)

Bob Rohr said:


> Here is the explanation for static pressure calculation.
> 
> As we all suspect Warno is on that fine edge with his static and cavitation, he has about 1.7 psi, the pump would like 2.  Since he cannot change the pressure change the temperature is his only viable variable.



But then he is getting less heat to his storage. His biggest Catch-22.


----------



## Marshy (Jan 18, 2018)

warno said:


> If I take a pressure reading on the suction side of the pump it would be vaccuum reading right? Or no?
> 
> I have a port on my suction side i can put a gauge on if this information would help us figure this out. And there's another port i can take a reading at the return just before going into the boiler.
> 
> View attachment 221052


No, very unlikely. If it was then the pump wouldn't actually pump anything it would become air bound. As the fluid enters the eye of the pump the pump is creating a low pressure from the suction of the impeller.  That low pressure is localized right in front of the impellar close to the moving vanes. Its just enough for some of the fluid to flash to vapor. It then recombines to liquid when it reaches a higher pressure, usually in the volute of the impeller. The collapse of the vapor bubble gives the noise you hear and can damage the surface of the impeller.


----------



## maple1 (Jan 18, 2018)

_If I take a pressure reading on the suction side of the pump it would be vaccuum reading right? Or no? _

Now we're getting into Point of No Pressure Change things. This thread keeps getting better. 

I had a hard time getting my head around that one. But theoretically, I THINK, if the top of the water in your boiler is the PONPC, and your circ was at that same spot, all the pressure diff generated by your circ, would go to the outlet side of the circ. So if it is very close to it, which yours is, then practically speaking, you should see all the pressure difference, at the outlet. I can picture it better with a closed system, and expansion tank connection - so this is a bit different from that.


----------



## warno (Jan 18, 2018)

@Marshy so there is a positive pressure reading at the suction side of the pump. I understand with the pump not running you would see the pressure from the water weight but if the pump is drawing water down the pipe is it still reading positive pressure? Would a pressure reading at the suction side of the pump tell us anything we need to know? 

Keep tuned in @maple1 we're going to get this. Lol


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## Bob Rohr (Jan 18, 2018)

warno said:


> @Marshy so there is a positive pressure reading at the suction side of the pump. I understand with the pump not running you would see the pressure from the water weight but if the pump is drawing water down the pipe is it still reading positive pressure? Would a pressure reading at the suction side of the pump tell us anything we need to know?
> 
> 
> Keep tuned in @maple1 we're going to get this. Lol



If you pull a sub atmospheric condition, water boils  at lower temperatures.  Once you boil or create vapor hand that induces cavitation..  The vapor pressure is what determines that point, again pressure and temperature relationship.  Water will boil at 100° if you pull enough vacuum


----------



## warno (Jan 18, 2018)

So I would like to switch gears. I'm understanding my pump is going to be flirting with caviation basically no matter what I do besides running lower temperatures. I'll go ahead with the lowered pump location like talked about before and I'll plumb in the larger piping for good measure. 

But what I just realized, took me 2 years, is my FPHX is killing the heat transfer no matter what I do. It's only a 20 plate that measures 4 1/4" x 12" x 2". 

So my question is is it possible to hit a target of mid 180s with a HX that measures 5" x 12"? What plate count would that take? I haven't seen a 5 x 12 option on flatplateselect.com. I'd really like to stick with getting one from eBay and those are the dimensions that are in my price range for a new HX.


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## Bob Rohr (Jan 18, 2018)

warno said:


> So I would like to switch gears. I'm understanding my pump is going to be flirting with caviation basically no matter what I do besides running lower temperatures. I'll go ahead with the lowered pump location like talked about before and I'll plumb in the larger piping for good measure.
> 
> But what I just realized, took me 2 years, is my FPHX is killing the heat transfer no matter what I do. It's only a 20 plate that measures 4 1/4" x 12" x 2".
> 
> So my question is is it possible to hit a target of mid 180s with a HX that measures 5" x 12"? What plate count would that take? I haven't seen a 5 x 12 option on flatplateselect.com. I'd really like to stick with getting one from eBay and those are the dimensions that are in my price range for a new HX.




Yes you can size a HX to do that with close approach sizing.  Generally you would be running the A side 10- 20° hotter then what you want from B side.  But we have been down that road, running 190 just isn't very doable with an open system.

And one key number is still missing, the BTU output of the boiler?  So pick a reasonable number, my suggestion would be somewhere in the 120- 140 K actual output.  If you can get your hands on a combustion analyzer it would get you a good idea of the burn efficiency, I'd guess 70% when it is in it's sweet spot, with quality, dry wood?   So my guesstimate on actual output is based on the physical size of your unit and estimated efficiency.  it looks similar to a Royall wood boiler I opened once, and it ran in the 60% range

Most HX programs let you select close approach design, maybe try 185 input on the A side, 140K input, 12 gpm.  Enter that into your HX simulation and see where it takes you.

Obviously to get the two temperatures close to one another it takes more surface area.

As someone mentioned earlier the inexpensive brands, even though it looks like then plate count is high, it the surface are (square footage) that you want.

So if you use the simulator you have, note the Sq Ft on the one it selects for you, then be sure the E-bay version has the same area.

The sim you posted on Tuesday was on then right track, dial down the 199/ 190° numbers to 185/ 180 perhaps.  The gpm and BTU looked reasonable 10 gpm, 145K 

We did a long hand example of HX sizing in Idronics 6  once you see the math involved you learn to appreciate the SIM programs.


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## warno (Jan 19, 2018)

@Bob Rohr I designed my boiler based around a portage and main unit. My boiler is almost identical in dimensions and gallons as the "BL 34-44" on their website.

Here's their site

I can't tell you if my output matches that but the design is basically the same. They have a brochure you can click and look at a PDF to see the different units.

And you're right, that math does make me appreciate the online calculators. Looking at it makes my brain hurt. 

If I put in some numbers on flat plate and get this HX 






Basically i just take the cubic feet of those dimensions and search eBay for one similar. Is that right? 

So in this case i need to search for a .494 cubic feet HX?


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## jwise87 (Jan 19, 2018)

I have been slogging my way through the 45 page pdf someone posted earlier in this thread from idronics. If I read it right you can easily find the head pressure of an existing system by checking pressure both sides of the pump, which you guys were just talking about, but since this is an open system you should be able to come close by either using a reading of slightly above 0 or slightly above14.7 for the input side and just taking one pressure reading as close to the output of the pump as possible.

Talking about reading pressure at the input side, even if you insert a gauge and it shows 0 the absolute pressure there is still slightly above an atmosphere, unless your gauge shows a vacuum.

Last I don't think you can use the port at your return because it is after all the "loads" and will probably read some where near your resting pressure in the tank.


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## Bob Rohr (Jan 19, 2018)

36.8 square feet of heat exchange surface is what you need for those conditions.  I can't say for certain all brands are manufactured to the same quality or performance. 

 Ideally you would look for this same data from a HX manufacturer you are considering, to assure they had actually tested and confirmed the performance.  That is why just a BTU rating on a HX is a bit misleading.  As you know a lot of import knock off stuff is a value engineered product, I use the term engineered with tongue in cheek in this case. 

I've cut open quality HX and cheapos and there is a difference in the technology inside.

I would not worry so much about pressure at the circ, it would take an accurate and expensive gauge to read those low pressures accurately.  You really can't change that condition very much.  We paid $1300 for an accurate certified delta P gauge used for balancing.


----------



## warno (Jan 19, 2018)

Bob Rohr said:


> 36.8 square feet of heat exchange surface is what you need for those conditions.  I can't say for certain all brands are manufactured to the same quality or performance.



Ok here's a 90 plate on eBay for $310 shipped

If my math is right it's got 37.53 sq/ft of area.


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## Bob Rohr (Jan 19, 2018)

that should do the trick.


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## warno (Jan 19, 2018)

Bob Rohr said:


> that should do the trick.



Now my question is what can expect for pressure drop through that thing? Will my current pump be able to feed this HX?

These are the numbers posted on the eBay listing, but it's saying 26.66 gpm at a drop of .3 psi for a delta of 20 degrees. There's no way I could ever stuff 26 gpm through there.


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## maple1 (Jan 19, 2018)

Your dT would come down to what's happening on the other side of the HX. That's kind of a confusing chart, that doesn't help a whole lot to the big picture. But I guess it does provide a pressure drop at a certain GPM. Which one should be able to extrapolate from?


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## warno (Jan 19, 2018)

that chart is more confusing the more i look at it. It has many different models on there with there own flow rates but it doesn't show the 90 plate at a lower flow.


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## Bob Rohr (Jan 19, 2018)

Another suggestion to increase flow would be to remove the strainer basket from this Y strainer.  Even brand new, with a clean screen they have a few ft of pressure drop.  With any crud in there it adds more pressure drop.  Leave that basket in it for a day or two after any piping work to catch debris, then remove the strainer.

Always good to have isolation valves around components that will need service.  One valve at each boiler connection and on the other side of the last component.


----------



## warno (Jan 19, 2018)

Bob Rohr said:


> Another suggestion to increase flow would be to remove the strainer basket from this Y strainer.  Even brand new, with a clean screen they have a few ft of pressure drop.  With any crud in there it adds more pressure drop.  Leave that basket in it for a day or two after any piping work to catch debris, then remove the strainer.
> 
> Always good to have isolation valves around components that will need service.  One valve at each boiler connection and on the other side of the last component.



When I change the piping around I plan to add in a couple valves in some areas i didn't think about. The strainer is one of those areas.


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## heaterman (Jan 19, 2018)

Reading through this thread and thinking back over all the times I have seen this topic and others related to it discussed without end just makes my head hurt.
I should write a book or something to spare people the pain of doing things 5 times and still not understanding why it does not and will never work...

Here's a few bullet point comments regarding open systems, pumps and pipe size.

Fact 1
Open systems such as commonly found in factory built and home made wood burners present some issues that must be understood BEFORE attempting to pipe a system up.
Fact 2
These issues are related to simple laws of physics and if you try to cheat or circumvent them you will most definitely lose. EVERY TIME.
Fact 3
Many of these issues stem from undersized pipe/tube and oversizing pumps to try and compensate for the same. 
Fact 4
There is never time or money to do it right the first time. There will ALWAYS be money and time to do it over.
Fact 5
Open systems have issues not present in a pressurized (real boiler) system which will cause you to learn more than you ever thought existed about piping and pumping

There are 2 basic solutions.
*Seal the system and pressurize it...which opens another can of worms... but hey, your pumps wouldn't cavitate. 
*At a very elementary level... Double the size of tube you think you need and cut the size of the pump in half.
You'll spend more on tube, less on replacement pumps and your system will work.


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## warno (Jan 19, 2018)

@heaterman oh trust me I've learned a huge amount of information I never thought existed. Anyone that talks about building their own boiler I cannot stress enough to them they need to do the research. I unfortunately did not when I started building mine. Which is why I'm here proving your fact 4 correct.


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## jwise87 (Jan 20, 2018)

warno said:


> @heaterman oh trust me I've learned a huge amount of information I never thought existed. Anyone that talks about building their own boiler I cannot stress enough to them they need to do the research. I unfortunately did not when I started building mine. Which is why I'm here proving your fact 4 correct.



Reading this thread makes me realize I must have gotten lucky building my first owb, it ate pumps, but other than that it worked good. It had 3/4" piping and an 0013 Taco, proving one of @heaterman 's other points.


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## Marshy (Jan 20, 2018)

heaterman said:


> Reading through this thread and thinking back over all the times I have seen this topic and others related to it discussed without end just makes my head hurt.
> I should write a book or something to spare people the pain of doing things 5 times and still not understanding why it does not and will never work...
> 
> Here's a few bullet point comments regarding open systems, pumps and pipe size.
> ...


Very enlightening and comical, thanks for the laugh. 

Warno, I didn't bail on you. I m in the works of installing my own boiler and the whole family decided to get sick yesterday.  I will be back.


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## warno (Jan 20, 2018)

Marshy said:


> Very enlightening and comical, thanks for the laugh.
> 
> Warno, I didn't bail on you. I m in the works of installing my own boiler and the whole family decided to get sick yesterday.  I will be back.




That's fine I've got little ones that tend to catch the bugs going around. I understand, family first! 

My one question I'm hoping to get answered now is what kind of pressure drop at 10gpm I'll see if I go with that 90 plate HX I posted earlier. Also if the delta T will be excessively low. I mean the surface area is close to the one selection from flat plate, but a small dimensional HX i would think would have a higher pressure drop. I'm probably wrong but want to make sure. 

What is the formula to figure pressure drop in a HX? I do appologize if it's been posted, we've discussed alot in this thread.


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## Marshy (Jan 20, 2018)

No easy way to calculate the pressure drop from the htx. It usually comes from the manufacture. It seems common for the eBay htx's to be missing that sort of data. The rest of your system is fairly low head loss so I wouldn't worry too much about it but, depending on what low head pump you choose it could be a concern. Double edge sword.


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## maple1 (Jan 20, 2018)

Isn't there a way to extrapolate the drop in the table to a different flow?


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## warno (Jan 20, 2018)

Ok so another development here, just for fun I took a temp reading from the bottom plate of my water jacket. The bottom is hotter then the top.

Here's the back of the boiler just under my lower port.






And heres the front of the boiler right next to the fire box.






So with that in mind I don't think pulling from the lower ports would be a good idea for the cavitation fix. Lol

I'm thinking the only option is keep pulling from the top and then dropping the pump lower to the floor. What do you guys think?


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## Marshy (Jan 20, 2018)

maple1 said:


> Isn't there a way to extrapolate the drop in the table to a different flow?


There is only one data point, Im just not certain head loss is proportional to flow. It may be, I'd have to research a little. Even if not it's probably close enough for what we are dealing with. 

The chart says 0.3 psi head loss at 26.6 gpm. That's like 8.3" of water column. Lower flow would result in less head loss. Thsts minor incimparison to the head loss in the rest of the system. I really want to do some calcs when I get time.


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## jwise87 (Jan 20, 2018)

warno said:


> Ok so another development here, just for fun I took a temp reading from the bottom plate of my water jacket. The bottom is hotter then the top.
> 
> Here's the back of the boiler just under my lower port.
> 
> ...




According to this illustration from the document someone posted earlier that will do the same thing as pulling from the bottom. Heck, you could put the circulator in a hole if you wanted even more pressure.


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## warno (Jan 21, 2018)

I understand the concept in that drawing. Basically you draw up like a siphon then it goes down to the pump and you gain that much more column of water. But how well does it work I wonder? If it works great I'd be willing to try it beings how I'm going to be replumbing the suction anyway. I'd like to hear what others think on that illustration.


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## Marshy (Jan 22, 2018)

warno said:


> I understand the concept in that drawing. Basically you draw up like a siphon then it goes down to the pump and you gain that much more column of water. But how well does it work I wonder? If it works great I'd be willing to try it beings how I'm going to be replumbing the suction anyway. I'd like to hear what others think on that illustration.


No, it doesn't work the way you wrote it. Any of the piping above the atmospheric water level in the boiler does not add head to the pump, only friction loss from the lengrh of pipe. The head is negated by itself. The reason is you are lifting (rather, sucking) the water up on the one side and then adding it on the down side. Net change in ststic head is zero, only more fruction loss from extra pipe. That is why the reference is from centerline of the pump to the water level exposed to atmosphere. Only way to circumvent this is raising the water line exposed to atmosphere.


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## warno (Jan 22, 2018)

Marshy said:


> No, it doesn't work the way you wrote it. Any of the piping above the atmospheric water level in the boiler does not add head to the pump, only friction loss from the lengrh of pipe. The head is negated by itself. The reason is you are lifting (rather, sucking) the water up on the one side and then adding it on the down side. Net change in ststic head is zero, only more fruction loss from extra pipe. That is why the reference is from centerline of the pump to the water level exposed to atmosphere. Only way to circumvent this is raising the water line exposed to atmosphere.




That makes sense. back to the original plan of just dropping the pump. 

Did you happen to come across anyway to tell if the pressure drop through that 90 plate HX would kill me at 10 gpm feeding it?


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## Marshy (Jan 22, 2018)

If it's proportional to flow then you can expect 0.1 psi drop at 10 gpm.


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## maple1 (Jan 22, 2018)

warno said:


> That makes sense. back to the original plan of just dropping the pump.
> 
> Did you happen to come across anyway to tell if the pressure drop through that 90 plate HX would kill me at 10 gpm feeding it?



I poked around here:

https://www.brazetek.com/products/d...changers/90-plate-brazed-heat-exchanger-1-1/4

This is still pretty darned fuzzy. My head started to spin looking at all the combos in the selecting guide. Pressure drop isn't linear with flows, and it also depends on dT thru the plate, and temps. But the bottom line is that if the plate gives 0.3psi head loss at 26gpm, it will be less loss at lower gpm. In some of those chart values, doing a simple linear calc is close, but others are a bit off. I would guess that a guess of 0.1psi at 10gpm would be ballpark. Or 2-3" of head. Which isn't very much.


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## warno (Jan 22, 2018)

So the added head loss from that HX wouldn't be a huge deal then if that is correct. Because in my calculations of my ~20ft of head we rounded up to get there.


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## leon (Jan 22, 2018)

Your boiler is going to steam, not good!! 
If you lower the high limit to 160 and the low limit to 140 being summer operating temps 
your going to have many fewer problems.

If you do that you can leave your circulator and its suction on the bottom using a much 
larger circulator at a lower pressures and temperature.

When your circulator suction is not flooded you are inviting quick circulator failure.

You need at least one set of isolation valves with gauge ports. 
This is to to keep track of outlet pressures P.S.I.G. on your circulator and you need to 
have an isolation valve with a port for a vacuum gauge to be sure you are not cavitating 
which will destroy the circulator. 

You have to remember that if your circulator inlet is that high in the water column it will love to suck in 
air bubbles that have not dissolved as air is lazy and will go everywhere.


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## warno (Jan 22, 2018)

leon said:


> Your boiler is going to steam, not good!!
> If you lower the high limit to 160 and the low limit to 140 being summer operating temps
> your going to have many fewer problems.
> 
> ...



Not sure where you read my boiler is streaming unless you are implying about my temp readings of over boiling point. and those readings were taken right next to the firebox, hottest spots, in the water jacket. But I can assure you I'm not losing any water due to stream. And what summer temps are you talking about? My boiler is shut down during the summer. And it's been 40s here lately, hardly summer.

If I drop my high limit to 160 then charging my 750 gallon storage tank is basically pointless. I can hit 160 in my storage on about 3-4 splits and a pile of kindling in the boiler.

The circ suction is always flooded. There is 8-9" of water above the suction port at all times.

My caviation is not from sucking air in it's from flashing to steam at the impeller inlet. We've already established this.

I'm not sure you've read through this whole thread.


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## leon (Jan 22, 2018)

I use Summer operating temperatures in my coal stoker all winter and they are set 
at 140 low 160 high with a fifteen degree differential. 

If your flashing to steam at the impeller that always indicates cavitation problems due to 
lower inlet pressures(vacuum) you need to move  the circulator to the bottom to have 
better flooded suction without having it go to steam at the impeller inlet and lower your 
operating temperatures.

With storage you already have thermal mass and it takes less energy to heat the 
water up to temperature and using summer temperature settings allow the system to 
respond faster too as the high limit is lower.     

You could use 160 low and 180 as the high limit with no issues.


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## warno (Jan 22, 2018)

leon said:


> I use Summer operating temperatures in my coal stoker all winter and they are set
> at 140 low 160 high with a fifteen degree differential.
> 
> If your flashing to steam at the impeller that always indicates cavitation problems due to
> ...




Once again I'm not sure you've read this thread. I understand the low inlet pressure and high temperatures is my problem. I cannot move my pump to pull from a lower port in my boiler because the bottom water is hotter then the top. Due to the design of my boiler.  If you scroll up in this page of the thread you'd see that. That's why I'm going to move the circ to the floor of the boiler shed and keep pulling from the top port but with bigger piping to the suction of the circ. By doing this I will gain a taller column of water above the circ inlet. 

I'm using a plate heat exchanger to charge storage because storage is pressurized and boiler is not. So I need hotter boiler water then 180 to get storage water close to 180.


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## maple1 (Jan 22, 2018)

leon said:


> I use Summer operating temperatures in my coal stoker all winter and they are set
> at 140 low 160 high with a fifteen degree differential.
> 
> If your flashing to steam at the impeller that always indicates cavitation problems due to
> ...



This has all been hashed over already in this thread. It's all here for your reading pleasure - all 8 pages (so far) of it.

[Is there a forum record for that kind of thing?  ]


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## Marshy (Jan 22, 2018)

Maybe they thought we were sharing chocolate chip cookie recipes for the last 7 pages?


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## warno (Jan 22, 2018)

So back on track here with the caviation issue.

I ,badly,  drew up some piping plans. which would be best or if someone has something better let me know. All of them put the pump on the floor of the boiler shed. And all supply piping will be 1.5" pipe and all fittings will be butt weld fittings. All return piping is 1" unless you guys think i should step that up too. Either way all fittings are butt weld fittings.

#1 basically just keep the same supply and return ports just bigger piping







#2 use both supply and return ports. Return feeding into the current return port mainly.






#3 use both supply and return. Return feeds into a tee to help split the return between ports.







And if you guys want to draw your own piping if you think a different way is better here's the shot I used.


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## warno (Jan 23, 2018)

@Marshy @Bob Rohr @maple1 You guy's still around? 

Anyone have a chance to look at the piping options i drew up? Anyone have a better way to plumb it?


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## Marshy (Jan 23, 2018)

warno said:


> @Marshy @Bob Rohr @maple1 You guy's still around?
> 
> Anyone have a chance to look at the piping options i drew up? Anyone have a better way to plumb it?


I'm in favor of #1 but slightly modified.  Keep the pump vertical and move the 90 degree elbow to transition to horizontal on the discharge of the pump.   The extra few inches difference will likely not be worth the added restriction of the elbow right in front of the inlet.  It will also add turbulence right before the pump and could exacerbate the cavitation.  Not for nothing but, if that don't fix it your looking at having to reduce the pump inlet temp.


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## warno (Jan 23, 2018)

@Marshy like this?


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## maple1 (Jan 23, 2018)

Maybe. You might do some numbers, on equivalent feet of pipe to an elbow. And also work in what height difference you would gain by going horizontal. Also the more straight pipe you can get behind the circ, if the circ is horizontal, the less chance for that turbulence effect. Kind of hair splitting stuff on a fuzzy 'maybe' situation.

As far as your piping choices - since you won't gain any more height no matter what you do there, it might not make any difference cavitation-wise, on its own. I would likely decide, based on where your coldest & hottest spots are. Pull from hottest, return to coldest. Since your main goal is to sent hottest water to storage. Which might also help internal boiler flows. If, say, the top RH outlet has water just as hot as top LH, or hotter, I might T them together. But if top RH is cooler, I likely wouldn't. Yes it would reduce cavitation potential, but just by decreasing circ inlet temp. Which would in turn send cooler water to the HX. The old Catch-22. Similarly, if the bottom LH inlet location is as cool as the bottom RH, I might T those together. But likely wouldn't if bottom RH is consistently the cooler.


----------



## warno (Jan 23, 2018)

We have a pipe bender at work that can put a long sweep 90 in the 1.5" if that would make the turbulence factor less. What's the rule of thumb on minimum length of pipe after a elbow to a circ?


----------



## Marshy (Jan 23, 2018)

warno said:


> We have a pipe bender at work that can put a long sweep 90 in the 1.5" if that would make the turbulence factor less. What's the rule of thumb on minimum length of pipe after a elbow to a circ?


The general rule of thumb is there should be a straight section 5-10 times the pipe diameter between pump inlet and any obstruction (valves, tee's, elbows etc.).

Another general rule of thumb is the piping diameter should be equal or one size larger than the pump inlet in an effort to limit suction piping velocities to 7 to 8 ft per second or less.

20 gpm through a 1" pipe is 8.17 ft/sec.
15 gpm through a 1" pipe is 6.13 ft/sec

20 gpm through a 1.5" pipe is 3.63 ft/sec.


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## warno (Jan 23, 2018)

I measured the boiler tonight. From the top of the water jacket to the floor of the shed is 60". So at best I'm getting a useable 58" of water column. 

If I plumb like this would it gain me anything at all? It's similar to the earlier posted illustration but doesn't go above the water line.


----------



## maple1 (Jan 23, 2018)

What aspect of that are you wondering about?


----------



## warno (Jan 23, 2018)

maple1 said:


> What aspect of that are you wondering about?



If it would gain me any extra water column to add those few precious psi at the pump inlet I'm chasing.


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## maple1 (Jan 23, 2018)

Still not sure what you mean by 'like this'. If you mean the short section that goes down into the water that won't do anything. If the pic shows greater vertical separation between circ and water level then probably?


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## warno (Jan 23, 2018)

maple1 said:


> Still not sure what you mean by 'like this'. If you mean the short section that goes down into the water that won't do anything. If the pic shows greater vertical separation between circ and water level then probably?



 If I just pull straight off the water surface it will draw air into the pump. The little drop down piece is a dip tube to insure the pump doesn't suck air in. 

Will the added height of the pipe headed to the pump benefit any from doing this? I mean As far as the water column pressure goes.


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## maple1 (Jan 23, 2018)

Still not completely grasping. Are you talking about raising your boiler outlet up higher - to the water height? Your outlet isn't up to water level now, is it? If not and you aren't increasing vertical separation I don't think you'd gain. But I still might be misunderstanding.


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## warno (Jan 23, 2018)

maple1 said:


> Still not completely grasping. Are you talking about raising your boiler outlet up higher - to the water height? Your outlet isn't up to water level now, is it? If not and you aren't increasing vertical separation I don't think you'd gain. But I still might be misunderstanding.




I just realized my drawing makes literally no difference other then more parts. The water level above the port is pushing down on the pump regardless where the port is in the water jacket. 

Disregard my above 3 posts.


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## maple1 (Jan 23, 2018)

We're in too deep to start disregarding, lol...


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## warno (Jan 23, 2018)

maple1 said:


> We're in too deep to start disregarding, lol...



Lol. very true.


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## warno (Jan 24, 2018)

I drew up a piping plan for this project, let me know if you guys think I should change anything. 

I went with the circ horizontal to gain about 6" more height to the center line. The 48" length of pipe coming out of the supply is using my current port location.  With that there will be a total of 56" of water above the pump center line.


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## BoiledOver (Jan 24, 2018)

Did you consider placing the new heat exchanger in the boiler room? That would make for a very short boiler loop (lower head) and using a lower head circulator. The Grundfos 15-58 here pushes 2 gpm on low, 7 gpm on medium, and 13 gpm on high. It sees no more than a difference of 9-1/2 feet of head as per the pressure gauged bypass loop. It is 15 feet each way of 1 inch copper with 20 fittings, a strainer, air eliminator and Danfoss valve. I did not include the various isolation valves as they are all full port. It would mean adding another circulator, the 15-58 is $82 US or four for $315. The boiler loop circ after the plate exchanger for it to see cooler temps.


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## warno (Jan 24, 2018)

BoiledOver said:


> Did you consider placing the new heat exchanger in the boiler room? That would make for a very short boiler loop (lower head) and using a lower head circulator. The Grundfos 15-58 here pushes 2 gpm on low, 7 gpm on medium, and 13 gpm on high. It sees no more than a difference of 9-1/2 feet of head as per the pressure gauged bypass loop. It is 15 feet each way of 1 inch copper with 20 fittings, a strainer, air eliminator and Danfoss valve. I did not include the various isolation valves as they are all full port. It would mean adding another circulator, the 15-58 is $82 US or four for $315. The boiler loop circ after the plate exchanger for it to see cooler temps.




The only problem with putting the FPHX in the boiler shed is heat dump reasons. If I have the HX out there I can't use heat dump to heat my garage. Essentially any dumped heat is wasted in the boiler shed which doesn't need anymore heat in it. Ambient air in the shed is right around 130° while burning. I really like the idea of the heat dump being in the garage where i could use heat. Even though i know the dump zone won't run all the time.


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## maple1 (Jan 24, 2018)

I was also wondering about the heat dump. How much does it actually get used? Theoretically a dump zone should only come into play in an overheat situation. So for max overheat protection, it should likely go up high right above the boiler (if possible). Maybe drawing from the other top boiler tapping. With a NO zone valve in between & separate aquastat & controller to control it. Have you ever had a power outage issue when burning? That might be the most common cause of an overheat - and I don't think your setup would offer any protection in that situation. That would also do away with the diverting valve  & possible head loss from that. Then if you wanted to heat the garage, just pull from storage for that. Then again - I don't think I have seen many OWBs with any kind of heat dump circuit. They just kind of seem to bubble for a bit. So maybe it's not needed at all if you have a decent depth of water above the firebox?


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## BoiledOver (Jan 24, 2018)

Just some thoughts from an alternate perspective.

Yeah, I see how the added heat in the boiler shed is a concern. I do not have experience with a FPHX but would think they can be insulated. Rigid polyiso can be cut to size, has good r-values, and is heat rated for use around hydronics. Easily assembled and dis-assembled.

The dump zone theory wouldn't change since it is over at the garage and could remain. If the dump zone is drawing heat away from the FPHX, it truly does not matter the location of the FPHX, does it? The piping is the pathway and will still exist.


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## warno (Jan 24, 2018)

maple1 said:


> I was also wondering about the heat dump. How much does it actually get used? Theoretically a dump zone should only come into play in an overheat situation. So for max overheat protection, it should likely go up high right above the boiler (if possible). Maybe drawing from the other top boiler tapping. With a NO zone valve in between & separate aquastat & controller to control it. Have you ever had a power outage issue when burning? That might be the most common cause of an overheat - and I don't think your setup would offer any protection in that situation. That would also do away with the diverting valve  & possible head loss from that. Then if you wanted to heat the garage, just pull from storage for that. Then again - I don't think I have seen many OWBs with any kind of heat dump circuit. They just kind of seem to bubble for a bit. So maybe it's not needed at all if you have a decent depth of water above the firebox?



My heat dump is for an over fire situation. The way it works is,  there's a temp sensor strapped onto the boiler supply side of the FPHX. When it is reading 195 the diverter valve opens to dump zone air/water heat exchanger where that fan also kicks on. When boiler cools down enough the diverter closes the dump port and switches back to the FPHX side for storage charging. Its a NO valve to the FPHX, NC to the dump zone. 

Take this for what's it's worth, I'm doing my damndest to not be the "typical" OWB owner. I'm doing batch burns to heat storage. I hate to see my boiler go into idle mode. If it's not burning full out it's not what i want. So if I overload the box for the amount of heat into storage then I want my boiler to just lose heat to my garage instead of idling. 

We very very rarely have power loss in my area. If, big if,  power goes out a damper kills the fire via idling.


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## maple1 (Jan 24, 2018)

Do you get over 195 very often though? With other changes being made - that might tend to happen even less, if those changes get more heat moving into your storage. It likely won't hurt anything to just leave it in place as-is. Aside I guess from moving it lower for reasons already mentioned somewhere else in the last 9 pages. But if for some reason you end up looking for a place where you could get just a little more pressure drop out of the circuit, that would be one place to look.


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## BoiledOver (Jan 24, 2018)

warno said:


> My heat dump is for an over fire situation. The way it works is, there's a temp sensor strapped onto the boiler supply side of the FPHX. When it is reading 195 the diverter valve opens to dump zone air/water heat exchanger where that fan also kicks on. When boiler cools down enough the diverter closes the dump port and switches back to the FPHX side for storage charging. Its a NO valve to the FPHX, NC to the dump zone.


Yes, this can still happen with the FPHX in the boiler shed. The storage loop is cooling the boiler loop. Your existing diverter valve for the dump will do the same with the storage loop as it has with the now long boiler loop. Making a much shorter boiler loop should result in less pressure and lowering the boiler circ should cause reduced pressure. Combined even better. Your storage will become additional dump zone.


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## warno (Jan 24, 2018)

maple1 said:


> Do you get over 195 very often though? With other changes being made - that might tend to happen even less, if those changes get more heat moving into your storage. It likely won't hurt anything to just leave it in place as-is. Aside I guess from moving it lower for reasons already mentioned somewhere else in the last 9 pages. But if for some reason you end up looking for a place where you could get just a little more pressure drop out of the circuit, that would be one place to look.



I'm hoping that with the new addition of the bigger HX it won't reach those temps. But if it does I'm wanting to use the heat appropriately. I think boiled over is on to something. 



BoiledOver said:


> Yes, this can still happen with the FPHX in the boiler shed. The storage loop is cooling the boiler loop. Your existing diverter valve for the dump will do the same with the storage loop as it has with the now long boiler loop. Making a much shorter boiler loop should result in less pressure and lowering the boiler circ should cause reduced pressure. Combined even better. Your storage will become additional dump zone.



I'll draw up another plumbing plan and post it in a little while. I think you are right. If the dump is cooling the HX it is in fact cooling the boiler.


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## BoiledOver (Jan 24, 2018)

After thinking through my post, I realize I stated lowering the circ would decrease pressure. Quite the opposite. You are looking to increase outlet pressure to cure your cavitation. But, a reduced boiler loop, larger FPHX, and different circulator may address the cavitation issue anyway.


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## Marshy (Jan 24, 2018)

warno said:


> If I just pull straight off the water surface it will draw air into the pump. The little drop down piece is a dip tube to insure the pump doesn't suck air in.
> 
> Will the added height of the pipe headed to the pump benefit any from doing this? I mean As far as the water column pressure goes.


No.
The pumps I drew all have one thing in common, the same amount of static head (ignoring pipe friction loss). That's because the pump centerline to the water level is the same.


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## warno (Jan 24, 2018)

The circulators I'm running right now are a B&G NRF-36 and a Grundfos 15-58. With this new drawing should I run the 15-58 at the boiler side and the NRF-36 at the storage side? 

here's my new drawing I just scribbled up.


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## warno (Jan 24, 2018)

@Marshy Thank you for the drawing. That makes sense. I did finally realize that my thought on ther idea was irrelevant because the water level is the same pushing down regardless where my port is in the water jacket. 

We've began kicking around piping ideas now. I think we are getting somewhere.


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## BoiledOver (Jan 24, 2018)

warno said:


> @Marshy Thank you for the drawing. That makes sense. I did finally realize that my thought on ther idea was irrelevant because the water level is the same pushing down regardless where my port is in the water jacket.
> 
> We've began kicking around piping ideas now. I think we are getting somewhere.


Pertaining to the garage side: The B&G might be just right on the storage loop. However your location doesn't seem to sit right, shouldn't it be pulling from the diverting valve with the diverting valve plumbed on the cold side? Just a tee on the hot side.

Pertaining to the boiler room: Should the circ be pulling from cold side of the FPHX? 4 Isolation valves at the FPHX for maintenance? Or do they have a feature built in?

Maybe 2 15-58's would do the trick.


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## maple1 (Jan 24, 2018)

After looking at your last sketch I am thinking more that your dumping circuit could be redundant.

In an overheat situation - the diverter would direct flow around the dump zone HX, rather than through storage. But, unless storage is getting close to charged, storage usually would be able to send colder water back to the boiler, than the dump HX would with its dT, therefore have more potential to cool the hot boiler better. My storage stays quite cold on the bottom, until first lap of charging is done. Then it finishes up rather quick with second lap. But, then again, maybe it is better if it did happen when storage is getting topped - or if you have a lot of mixing when charging storage.

That might be more rambling to be spit aside with other stuff that has since been spit aside....

I will second BoiledOvers comment about the storage circ being not quite in the right place - it should be downstream from the T on that return line. The boiler circ comment - hmm, back to cooler inlet temps vs. increased inlet pressure drop.


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## warno (Jan 24, 2018)

maple1 said:


> After looking at your last sketch I am thinking more that your dumping circuit could be redundant.
> 
> In an overheat situation - the diverter would direct flow around the dump zone HX, rather than through storage. But, unless storage is getting close to charged, storage usually would be able to send colder water back to the boiler, than the dump HX would with its dT, therefore have more potential to cool the hot boiler better. My storage stays quite cold on the bottom, until first lap of charging is done. Then it finishes up rather quick with second lap. But, then again, maybe it is better if it did happen when storage is getting topped - or if you have a lot of mixing when charging storage.
> 
> ...



The heat dump is defiantly for when storage is charged and still have a fire burning. 

I agree with the storage circ being wrong. I redrew that part. 

I was wondering about the adding inlet drop if the boiler circ was on the return side. I think it might be alittle to much. 







@BoiledOver with strainers on both sides of the FPHX there shouldn't be much gunk in there. If it does plug up I have webstone propal valves at the ends of each line. I would just blow the lines out and remove the HX via unions.


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## BoiledOver (Jan 24, 2018)

warno said:


> @BoiledOver with strainers on both sides of the FPHX there shouldn't be much gunk in there. If it does plug up I have webstone propal valves at the ends of each line. I would just blow the lines out and remove the HX via unions.


Gotcha, you already had your plan for that.

Maybe @Bob Rohr or @Marshy will review the direction you are currently considering. Attached is a thought on how I would approach the design at the boiler. Enlarged discharge and circ down low, the return temp should rarely exceed 170F.

I have a hangup about keeping equipment (circs) cooler rather than warmer, in most cases, hence on the return. Just for a hoot, consider swapping the circs to see what happens before making any mods. Ya might get some feedback from the results.


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## warno (Jan 24, 2018)

I guess if I did put the circ on the return side of the HX I could pull from the bottom of the water jacket since that is where the hottest water is.

I could over size the piping going to the HX and up to the pump. The pump itself would still be below the water level by about 48" in that location and the only major head loss would be the HX and the themomix valve.

What does everyone else think about that idea? Too  much head loss for the suction side?


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## maple1 (Jan 24, 2018)

With that big hx you were looking at last I don't think that would be an issue. Looked like hardly any pressure drop I think?


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## BoiledOver (Jan 25, 2018)

heaterman said:


> I take it your boiler is not a sealed type you can maintain any pressure in?
> If so, you're going to find 180-185* is the maximum temperature you can run without destroying pumps.
> Also keep in mind that the higher the "head" is in the piping the more NPSH you need to maintain on the inlet of the circ.
> Larger diameter tube on the discharge side is the only thing that will accomplish that all other factors being equal.


#01-From @heaterman Is this correct?



Marshy said:


> This. You need to lower the pump and reduce the temp of the inlet. Enough of either one or a mix of both will solve the issue.


#02-From @Marshy  Is this correct?



warno said:


> I think the easiest thing I could do is replumb the suction side with bigger piping and move the circ to the floor level in a horizontal position.


#03-From you. This is contrary to #01. Whichever is correct can be implemented.

A bit of a sidebar, the noise you are hearing and calling cavitation could alternatively be the noise of radial thrust. Still an issue but seems to be a different symptom of the same contributing factors. A very basic article of radial thrust linked here.

If #01 and #02 are correct, you can leave the FPHX in place but change your plumbing as the image shows. You showed a similar piping scheme in your post #61 on page three although it was pulling from the boiler (hot) rather than pulling from the FPHX (cooler).


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## warno (Jan 25, 2018)

@BoiledOver the only thing wrong with leaving the FPHX in the garage and pulling from the return side was the tremendous head loss to the suction side of the pump. I don't remember what post it was but we've discussed it here somewhere. Lol 

I'm almost 100% certain the noise from the pump is caviation. It sounds like pebbles are running through the impeller. From what I've read that is the sound of the air bubbles bursting.


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## warno (Jan 25, 2018)

I drew up some scenarios of piping just the boiler side with the circ pulling from the return side of the HX. 

The hottest area of the boiler is the lower left corner and the coolest is the upper right corner. 

The larger looking pipes will be 1.25" and the smaller will be 1". 

Which do you guys think will work best.


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## maple1 (Jan 25, 2018)

I would do 1. But reasoning is sort of convoluted.

I would expect the hotter spot to be at one of the top ports. And cooler to be one of the bottom. And both top to be hotter than both bottom. But it doesn't seem to be that way - which might be a sign that when you are burning & circulating water thru the boiler, the flows through it aren't even and there are places inside that the water could be moving faster through. Or others where it is stalling. So if you go 1, that will make the biggest pipe at the places of biggest expected flow (hot top left & cool bottom right - where you are piped in now), but with ball valves at all outlets still let you bring flow to/from the other two ports to help you balance the flow through the boiler. I would likely have said connect the two top ports to supply, and two bottom ports to the return (call that 4?) - but what you said about the top right port is coolest has me a bit boggled there. Internal flow must be channeling up the right side, then over to the left along the top? But I would still expect to see bottom right (where you are returning to now) the coolest. Are those relative temps measured at the ports? Or are there front temps thrown in there too? I could see how bottom left might be hottest if not much water moving inside at that spot but can't see how top right could be coolest if return is coming in bottom right.

Depending how hard it is for you to do, I might do it all in 1-1/4" also. Then balance with ball valves.


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## warno (Jan 25, 2018)

@maple1 the temps I measured the hottest were on the water jacket bottom plate. The bottom plate just under the lower left port was reading right around 200° when the upper port itself, same side, was reading closer to 190°. The lower left side of the bottom plate was just a few degrees less then the right. But the upper left port, very little to no flow there,  was reading 170°. Right now the lowest flow points are the upper left and lower right. I'm looking to alleviate that by trying to get a cross flow affect. Because my firebox is only submerged by water on it's upper half it kind of makes sense the lower water jacket would be hottest. I also get a hot spot right at the front plate, by the wood loading door, of the water jacket because little flow gets up there. 

Here's a pic you can see my water jacket bottom plate compaired to the firebox body. The pipe sticking in there is my current return port.


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## BoiledOver (Jan 25, 2018)

warno said:


> @maple1 the temps I measured the hottest were on the water jacket bottom plate. The bottom plate just under the lower left port was reading right around 200° when the upper port itself, same side, was reading closer to 190°. The lower left side of the bottom plate was just a few degrees less then the right. But the upper left port, very little to no flow there,  was reading 170°. Right now the lowest flow points are the upper left and lower right. I'm looking to alleviate that by trying to get a cross flow affect. Because my firebox is only submerged by water on it's upper half it kind of makes sense the lower water jacket would be hottest. I also get a hot spot right at the front plate, by the wood loading door, of the water jacket because little flow gets up there.
> 
> Here's a pic you can see my water jacket bottom plate compaired to the firebox body. The pipe sticking in there is my current return port.
> 
> View attachment 221597


Just so ya know, take my advice with salt. I am just a fella who likes the DYI approach too. I had a pretty big (not dangerous) fail prior to getting an Eko boiler. Failed the research and engineering part.

That is a rather unique design you have built from. Is it all yours? Now I see why you have the oddball temps at the ports. You sure do have the welding skills, kudos to ya.

To me, supply from the top and return below is logical. So, I would do #3 but reversed. Combining both lower ports and both upper ports should help in keeping the top hotter than the bottom, instead of a criss-cross or side-to-side fashion.

If your plan includes a larger FPHX that has less head loss and you move it to the boiler shed, you should see big gains in the boiler loop efficiency. The results may put a damper on the new storage loop. If your storage loop is pressurized, no problem. If on the other hand it is unpressurized will you be able to get the flows needed to take all of what the PFHX is providing at 200F? Without the cavitation issue moving to that side? Maybe your original HX will keep up if you throttle back on the boiler output. I know you stated you wanted the big numbers in storage.

190-200F water temps in the boiler at regular operation, holy cripes. Is that how the owb fellas go? Those temps in storage will be sure to keep your garage warm, lol. The higher the storage temps means higher standby losses. During the coldest spells, I will run storage temps up to 190-192F. Generally 180-183F is the target.

After researching, I see where the larger pipe diameter is suggested on the inlet side to help in reducing cavitation issues. Anyway, it looks like you are on the right track with your plan. Circ low and away from the HX with larger piping.


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## warno (Jan 25, 2018)

BoiledOver said:


> Just so ya know, take my advice with salt. I am just a fella who likes the DYI approach too. I had a pretty big (not dangerous) fail prior to getting an Eko boiler. Failed the research and engineering part.
> 
> That is a rather unique design you have built from. Is it all yours? Now I see why you have the oddball temps at the ports. You sure do have the welding skills, kudos to ya.
> 
> ...




My design came from a manufactured boiler that is on the market. I changed some things to better match the parts I had to use. Thanks for the compliment. 

The storage is pressurized so the storage pump will like that.  If I throttle the heat transfer any lower with my current HX my boiler goes into idle mode. 

I'm not meaning to run 190° water all the time but once my storage hits 170° the heat transfer slows to a crawl and the boiler tends to get really hot really fast. With forced combustion I'm kind of stuck with the firing rate my fan drives air into the box. I am also getting secondary fire now  so that means more heat. I'm planning on switching to induced draft and being able to slow my firing rate substantially. If I can hit 180s in my storage with ease I'd be happy. After reading the temps everyone else uses that should be good.


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## Bob Rohr (Jan 26, 2018)

I'd agree, combine the boiler connections with reverse return piping, increase to 1-1/4 at the second connection.

The pump as low as possible.

The HX at the boiler.

Eliminate as many "devices as possible in the boiler piping.  I'd use a dirt separator not a Y strainer.  A brand new Y strainer has a few feet pressure drop, much worse as they plug up.  Near zero pressure drop in a separator.

Any time the boiler pump is off the boiler will stratify, basic thermodynamics, I'd use the top ports as supply connections.

Put the dump device, if you really need it, on the B side, that anti condensation valve, better in the pressurized side of the HX as the valve also has some pressure drop.

Long sweep turns are much better, less pressure drop.

I suspect with these changes you could use a low head, flat curve circ and help lessen cavitation potential.  Something like a Taco 0010 might get that 12- 14 gpm you are after.

You will still need a high head circulator on the B side to move 10GPM or more.  You can put pumps in series instead of paying the high $$ for high head circulators.


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## warno (Jan 26, 2018)

Bob Rohr said:


> I'd agree, combine the boiler connections with reverse return piping, increase to 1-1/4 at the second connection.
> 
> The pump as low as possible.
> 
> ...




I'll look into the dirt separator again. It was a matter of cost last time is why I went strainer. Might still be an issue. Not sure yet.

@Bob Rohr we've been talking about running the circ on the return side after the HX to help eliminate the cavitation issue. Would you agree with this or no? It looks like your drawing has the circ on the supply side.

Another question being the boiler protection valve I believe has to go on the boiler, open, side of the HX because the boiler water has to directly affect the thermostat inside the valve. Is this correct thinking? I'm just not sure how it would work on the other side without the heated water to open it.

As far as pumps go, I'm hoping to use my current 15-58 and NRF-36 I have now. At least to see if they can do the job before I buy another pump/s.


For separators how is this one?


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## warno (Jan 26, 2018)

I did find a hiccup with the return protection valve. It's a Caleffi Themomix valve with 1" MPT ports. The bigger option for the 1.25" valve is another $200 i would have to spend. So I think I'm going to run my 1" valve for now and if I see issues with it cutting flow to much I'll address it with a larger option. I'll have all the plumbing be 1.25" everywhere else but the valve. I do know this will be the bottle neck, but the 1.25" themomix valve has the same CV of 10 as my 1" valve. so other then the restriction in the ports themselves it would be about the same loss. 

heres the most recent drawing I drew up. It has the reverse return supply and return like Bob Rohr suggested but I drew the circ on the return side to take advantage of cooler temps for the circ. It does show strainers as well but I think I'll just pull the screens after alittle run time. 

Here's the boiler side






And the storage side


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## maple1 (Jan 26, 2018)

Maybe it's been mentioned already in this thread, but I wonder how much your thermomix is actually doing or needed? It's not like you will have cold storage bottom or radiant floor water wanting to get directly into your boiler. I guess the dT that you will be seeing across your new much bigger HX with this new setup has yet to be seen (unless someone can take a half-educated stab at trying to figure that out). Does your boiler spend much time now sending say <170° water to the HX? How do you control pump launch and what is that set at?


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## warno (Jan 26, 2018)

@maple1

 Right now the thermomix does absolutely nothing during normal operation. But if during warmer days when i don't fire everyday the boiler can dip into the 140s-130s and the themomix does it's thing at that point. The pump runs as long as the flue temp doesn't drop below 200° and it's started when I push the "go" button to start the firing cycle. The "go" button turns on the boiler pump, storage pump, and combustion fan. It's all held in the "on" position via a contactor controlled by the flue temp.

And like you said the delta T of the new HX is yet to be seen so it sort of has me worried. On the possibly the delta T isn't crazy low I could just take out the Themomix valve and put in some tees with a manual bypass for season start up process. I'm just worried the deltaT will be lower then I'd like to see so I'd like to keep the throttling affect of the themomix valve.


EDIT:

I Did just look at the price of the danfoss protection valve. It's cheaper and has a CV of 16.2 for the 1.25" valve


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## BoiledOver (Jan 26, 2018)

Since your boiler loop goes through the HX only, your boiler return will be decided by the deltaT. Say the HX delta averages about 20F, you can control the boiler return by controlling your boiler and storage circs with one aquastat set at 165F ON and 160F OFF. This will result in boiler return staying above 140F. The Johnson 419 is affordable and works nicely however you choose to set them up, break on rise or fall, cool or heat. They provide adjustable hysteresis and such.

Notice the link is not to a 419, it has been discontinued and the 421 is the replacement.


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## Bob Rohr (Jan 26, 2018)

warno said:


> I did find a hiccup with the return protection valve. It's a Caleffi Themomix valve with 1" MPT ports. The bigger option for the 1.25" valve is another $200 i would have to spend. So I think I'm going to run my 1" valve for now and if I see issues with it cutting flow to much I'll address it with a larger option. I'll have all the plumbing be 1.25" everywhere else but the valve. I do know this will be the bottle neck, but the 1.25" themomix valve has the same CV of 10 as my 1" valve. so other then the restriction in the ports themselves it would be about the same loss.
> 
> heres the most recent drawing I drew up. It has the reverse return supply and return like Bob Rohr suggested but I drew the circ on the return side to take advantage of cooler temps for the circ. It does show strainers as well but I think I'll just pull the screens after alittle run time.
> 
> ...




It is alway wise to avoid any flow restricting devices on the suction side of a circulator.  In your case especially, since you are on a fine line of cavitation with pressure/ temperature.  Circs are built to handle 225°.

Plenty of other ways to prevent return condensation on the secondary side, as others have suggested.  Viessmann and others use a simple 140° control on the return or boiler itself to turn the circ off, a primitive/ bang-bang approach but it doesn't cost you any piping penalty.

In your case I feel you have plenty of HP and return temp protection should not be a big concern.  You have bigger fish to fry.  It seems you are converting more energy that you can dissipate.  

Only on cold start up would you have some condensing.  All boilers start cold at some point, the key is to minimize that cold run time.  The rule of thumb is to have return temperature above dew point within 10 minutes or so of start up.


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## warno (Jan 26, 2018)

BoiledOver said:


> Since your boiler loop goes through the HX only, your boiler return will be decided by the deltaT. Say the HX delta averages about 20F, you can control the boiler return by controlling your boiler and storage circs with one aquastat set at 165F ON and 160F OFF. This will result in boiler return staying above 140F. The Johnson 419 is affordable and works nicely however you choose to set them up, break on rise or fall, cool or heat. They provide adjustable hysteresis and such.
> 
> Notice the link is not to a 419, it has been discontinued and the 421 is the replacement.




With that idea would I tie the sensor to the return pipe or water jacket? I'm not sure if turning the pump on and off with the return drop is what I would want or I'm not thinking about it right. 

I'm thinking with the sensor tied to the return pipe of the pump shuts off at say 150 there would be no hot water flow to turn it back on. Maybe I'm thinking about it wrong.

My concern with return temps is with my current baby 20 plate HX and low storage temps I'm easily seeing 30° delta T. If I'm going with that 90 plate and bigger dimensions then I would be seeing alot higher delta Ts. I mean with little to no head on the boiler loop i know i will be running alot more gpm which helps delta but the protection valve just seems smart.


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## Bob Rohr (Jan 26, 2018)

For return protection the goal is to stop or divert flow when the boiler is running to cool (cold 

In your unique case we are trying to come up with the least problematic method.  Put the sensor wherever it gets a sample of the boiler conditions.  In your boiler the design may be fine with cool return if it blends quickly with all the volume inside and prevents condensing conditions. 

 It will be obvious quickly in wood fired appliances as you will see condensation in the flue, and creosote forming quickly.  Monitoring flue temperature is also and indicator, although it looks like you don't have low temperature issues there?

In some cases manufacturers build sloppy, inefficient HX on purpose.  A typical gas fired WH has a fairly inefficient HX design so it can handle low incoming water temperatures on a continuous basis, hence the high flue gas temperatures and  low efficiency numbers.


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## warno (Jan 26, 2018)

@Bob Rohr I only get creosote if my boiler goes into idle mode. Other than that it's  just soot and fly ash. 

I just threw this idea together. What about a simple manual bypass I could throttle and possibly find a happy medium for return temps throughout the burn.

I know you said the idea is to not have any devices on the suction side but I think we are all in some agreement that 90 plate doesn't have alot of loss. Here's to drawings one with the circ on return one with the circ on supply. Both with the manual bypass idea. All large looking piping would be 1.25" and all smaller would be 1".

Option #1







Option #2


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## BoiledOver (Jan 26, 2018)

warno said:


> With that idea would I tie the sensor to the return pipe or water jacket? I'm not sure if turning the pump on and off with the return drop is what I would want or I'm not thinking about it right.


Mounted to the top of the boiler would be my choice. Definitely not on the return.



warno said:


> I'm thinking with the sensor tied to the return pipe of the pump shuts off at say 150 there would be no hot water flow to turn it back on. Maybe I'm thinking about it wrong.


You have a good sense of reasoning. Definitely not on the return.



warno said:


> My concern with return temps is with my current baby 20 plate HX and low storage temps I'm easily seeing 30° delta T. If I'm going with that 90 plate and bigger dimensions then I would be seeing alot higher delta Ts. I mean with little to no head on the boiler loop i know i will be running alot more gpm which helps delta but the protection valve just seems smart.


Wish I knew more about heat exchangers but hadn't had the need to know. As I stated in another post, maybe your current FPHX is up to your task, I do not know. You have already crunched the numbers concerning an appropriate size.


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## Bob Rohr (Jan 26, 2018)

The top of the boiler will or should be the hottest point, it may not respond accurately to cool return.  
The valve you have now watches and responds to return temperature to assure you stay above the condensation setpoint, probably has a 140F sensor in it.    You would need circulation of course for a return sensor to be accurate.

All the tekmar controls show return protection sensor on return piping.  As do boiler installation manuals, Taco ∆T circulators, etc.


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## warno (Jan 26, 2018)

Bob Rohr said:


> The top of the boiler will or should be the hottest point, it may not respond accurately to cool return.
> The valve you have now watches and responds to return temperature to assure you stay above the condensation setpoint, probably has a 140F sensor in it.    You would need circulation of course for a return sensor to be accurate.
> 
> All the tekmar controls show return protection sensor on return piping.  As do boiler installation manuals, Taco ∆T circulators, etc.




Yes it is the 140° sensor in my protection valve. In a drawing you posted earlier it didn't show the protection valve at all.  Do you think i really need it? 

Ever year at the start of the season I get condensation in my boiler with the first fire of the season. And ever year the condensation stops when the water jacket gets to 110-115°. Am I to believe that as long as my water jacket doesn't dip below 120 that it should be a non issue?


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## Bob Rohr (Jan 26, 2018)

Skip the return protection valve.  IF you had a high tech gasification style it would be a must have. 

 I think your design is closer to an OWF and I've never seen the need to protect them.  That combined with the operating method you describes make it sound like it will never have a chance to cool down.

I'd run the boiler pump any time you are firing.  If needed, just drop off the secondary side circulator, to allow the boiler to catch up.

A simple aquastat, setpoint control or snap disc stat could be added to pulse that B side circ without getting in to the piping again.

Keep the goal in mind, remember we are trying to simplify and address the two basic problems you are having.


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## warno (Jan 27, 2018)

Bob Rohr said:


> Skip the return protection valve.  IF you had a high tech gasification style it would be a must have.
> 
> I think your design is closer to an OWF and I've never seen the need to protect them.  That combined with the operating method you describes make it sound like it will never have a chance to cool down.
> 
> ...



Ok I will leave out the protection valve. Worst case is I do see the need for it and can put it in later. At season start up I'll just shut off the storage pump until the boiler is hot, which is how I've been doing it since adding storage. 

I agree with the thought of the boiler pump running at all times during a burn cycle. I will add an aquastat to cut the storage side pump if the boiler water jacket gets to low.


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## warno (Jan 30, 2018)

So I've done another drawing I'd like some feed back on. After measuring my plumbing closet in the garage my only option to get the circ where I want it before hitting the pex to go out to the boiler is I have to go up with the piping first then go into the circ. The storage side is pressurized so if I'm understanding correctly it shouldn't matter on this side. It is about a 24" rise then horizontal then into the pex underground. There will be at least  10" of 1"  straight pipe before the pump suction port. Will this work? 






On a side note, I did draw in a strainer simply because I already have one and like Bob Rohr said I could just pull the screen after a few weeks of running.


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## maple1 (Jan 30, 2018)

Yes should be OK if pressurized. I would plumb in a vent on that high spot, or some kind of bleeder valve - it would likely make for a place for air to get hung up in. Same for all high spots, actually.


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## warno (Jan 30, 2018)

maple1 said:


> Yes should be OK if pressurized. I would plumb in a vent on that high spot, or some kind of bleeder valve - it would likely make for a place for air to get hung up in. Same for all high spots, actually.



Ok Thanks. 

All valves in that drawing will be webstone pro pals and I'll be using the garden hose for purging so it should clear out pretty easy. 

I've been meaning to ask this for awhile now but what pressure does everyone run their systems at? I've seen mine up to 10 psi at 170° but I'm wondering if I should bump it up alittle more.


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## maple1 (Jan 30, 2018)

10 should be OK. It comes down to where exactly that is measured at, and how high the system goes above that point. Static 10 at the circ should be good for 15' or so above that of system height. But I would assess that, at cold system temp - i.e., if that 10 drops to say 5 when cold, that would only be good for maybe 8' of system height. (roughly roundly talking).

BTW, is that expansion tank a bladder?(I feel like that has been talked about before). It should likely be T'd in, on the suction side of the circ - by rights and popular hydronic heating thinking. Although practically speaking, with adequate system pressure, may not be an issue.


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## warno (Jan 30, 2018)

maple1 said:


> 10 should be OK. It comes down to where exactly that is measured at, and how high the system goes above that point. Static 10 at the circ should be good for 15' or so above that of system height. But I would assess that, at cold system temp - i.e., if that 10 drops to say 5 when cold, that would only be good for maybe 8' of system height. (roughly roundly talking).
> 
> BTW, is that expansion tank a bladder?(I feel like that has been talked about before). It should likely be T'd in, on the suction side of the circ - by rights and popular hydronic heating thinking. Although practically speaking, with adequate system pressure, may not be an issue.



That 10 psi was measured on my upper temp/pressure gauge that's in my supply header for my tanks. That's why I was wondering about it. I'll watch it to see how far it drops at a cooler temperature.

My expansion tank is a non bladder that sits up in the rafters of my garage. The top storage tank in the stack has a fitting on its top that goes up to the expansion tanks.  It seems to work pretty well so far.


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## maple1 (Jan 30, 2018)

warno said:


> That 10 psi was measured on my upper temp/pressure gauge that's in my supply header for my tanks. That's why I was wondering about it. I'll watch it to see how far it drops at a cooler temperature.
> 
> My expansion tank is a non bladder that sits up in the rafters of my garage. The top storage tank in the stack has a fitting on its top that goes up to the expansion tanks.  It seems to work pretty well so far.



I'd just go with it then.

The basic principle is, that if you tie it in at the circ inlet, then all the pressure diff that the circ makes, will show up at the outlet. I.e., if your circ can generate 5 psi of dP, the inlet pressure will stay the same and the outlet will rise that 5 psi. So good for cavitation prevention since inlet pressure won't drop. By contrast, if it was tied in at the outlet, all the dP would show at the inlet - the outlet pressure would stay the same and inlet would drop the 5 psi. Which could be bad for cavitation. Yours might give an in-between result, each side moving a couple pounds in opposite directions - likely no concern with adequate system pressure. I don't know if bladder vs. non-bladder plays any kind of part in all that, but thinking not.

Carry on.


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## warno (Feb 4, 2018)

maple1 said:


> 10 should be OK. It comes down to where exactly that is measured at, and how high the system goes above that point. Static 10 at the circ should be good for 15' or so above that of system height. But I would assess that, at cold system temp - i.e., if that 10 drops to say 5 when cold, that would only be good for maybe 8' of system height. (roughly roundly talking).



I just realized that my 10 psi reading was on my bottom pressure gauge of my tank. So that was basically the weight of the water. My top gauge was only reading a few pounds at 150 degrees today. Top gauge has about 12" of water above it. Should I add some pressure to my storage tanks?


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## maple1 (Feb 4, 2018)

Should be ok if there's only a foot of water above it. But is there any part of the system that goes higher than that? Dump circuit?


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## warno (Feb 4, 2018)

Nothing gets above that pressure as far as I know.  The dump circuit is tied into the open side of the system right now. 

Here's a picture of my top gauge. It shows temp and pressure. As you can see its barely, if at all, reading any pressure.


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## maple1 (Feb 4, 2018)

What I meant was higher in elevation. Tank top is highest system point? What's the elevation diff between bottom gauge and very top of system? I take my readings with a grain of salt when they are at the lowest limit of the gauge.


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## warno (Feb 4, 2018)

maple1 said:


> What I meant was higher in elevation. Tank top is highest system point? What's the elevation diff between bottom gauge and very top of system? I take my readings with a grain of salt when they are at the lowest limit of the gauge.



Ok,  the highest point in the system is the water/air HXs in the garage rafters. They are about 9ft off the floor. The lowest gauge is about 6" off the floor. And this is all in the closed side of the system. The top of the tank stack is 7ft 10in off the floor. 8 ft ceilings in the garage.


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## maple1 (Feb 4, 2018)

10 psi at your bottom gauge should be around 6-7 at the top then. Which should be good.


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## Bob Rohr (Feb 6, 2018)

To measure the pressure at the bottom of your open system boiler you will need a very low scale, accurate gauge.  A 5' column of water exerts 2.1 psi.  Not many of those inexpensive tridicators will even read that low.

A manometer reading inches of water volume would be accurate.  Or just do the math .433 psi to lift water 1 foot.

On the pressurized side ideally you want 5 psi at the highest point.  So if the high point is 12' X .433= 5.2, add 5 for a 10 psi gauge reading.

Depending of course on where the gauge is located in the piping.


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## warno (Feb 6, 2018)

Bob Rohr said:


> To measure the pressure at the bottom of your open system boiler you will need a very low scale, accurate gauge.  A 5' column of water exerts 2.1 psi.  Not many of those inexpensive tridicators will even read that low.
> 
> A manometer reading inches of water volume would be accurate.  Or just do the math .433 psi to lift water 1 foot.
> 
> ...




The open side I know now I can only raise the pressure by added water height. But my closed storage side is what I was mainly asking about.

Here's a picture of my gauge locations. You can see the top gauge installed and the red arrowed circle is the port my bottom gauge is in. The top of the top tank is at 7ft 10in.


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## maple1 (Feb 7, 2018)

*The top of the top tank is at 7ft 10in.*

Plus you would also add on how far up the piping thru the ceiling or whatever else is hooked to the tanks also goes from there to get total dH. Then x 0.4psi/foot.


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## warno (Feb 7, 2018)

maple1 said:


> *The top of the top tank is at 7ft 10in.*
> 
> Plus you would also add on how far up the piping thru the ceiling or whatever else is hooked to the tanks also goes from there to get total dH. Then x 0.4psi/foot.



So any plumbing at all above the ceiling adds pressure down on the tanks? Even if it's the heating loops?


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## maple1 (Feb 7, 2018)

Yes. As long as it's connected.


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## Marshy (Feb 11, 2018)

Looks like I have a lot to catch up on.


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## warno (Feb 18, 2018)

I'm hoping some of you are still watching this thread and could help me out here.

 My boiler has been idling ALOT lately, like it's not shedding the BTUs as it should. I know we all know my current plumbing and my current HX is less than ideal. But I'm at a loss because it seems the boiler is firing great but the storage just isn't taking it. I mean even worse then before. I pulled the screen on my boiler side strainer and it was, to my amazement,  perfectly clean. I didn't pull the storage screen though. I'm getting a delta t of 40°+ on the boiler side and only 10°-15° on the storage. Boiler side pump on speed 2 and storage on speed 3. Boiler is pushing 185 as I'm writing and storage is at 140s. Storage should be climbing pretty fast right now but isn't. 

Should i pull the storage screen and see if there's blockage that slowing flow or what should I check. I'm just trying to get through the rest of the season at this point.


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## TCaldwell (Feb 18, 2018)

Descale the hx


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## BoiledOver (Feb 18, 2018)

Delta temp of 40F says the btus are going somewhere. What is the flow temp going into the HX from the boiler? Is it close to the boiler out temp? If not, ouch.

Are you still running the monster circ on the boiler and the 15-58 on the storage? Do you know the flow rates of the two circulators at each speed? I do not know of the HX specs, but the 15-58 on high will probably push somewhere around 14 gpm with your short storage loop.


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## warno (Feb 18, 2018)

TCaldwell said:


> Descale the hx



I was wondering this but it just started all of the sudden. I'd say within the last week or so. 



BoiledOver said:


> Delta temp of 40F says the btus are going somewhere. What is the flow temp going into the HX from the boiler? Is it close to the boiler out temp? If not, ouch.
> 
> Are you still running the monster circ on the boiler and the 15-58 on the storage? Do you know the flow rates of the two circulators at each speed? I do not know of the HX specs, but the 15-58 on high will probably push somewhere around 14 gpm with your short storage loop.



Boiler temp in is ~180 and out ~140. Storage in is ~130 and out ~142-145. I used to see a 30° drop on boiler side to a 25° gain in storage. My temp readings were on the HX ports on both sides. 

I'm still running the same circs. Nrf-36 boiler side, 15-58 storage side.  My boiler side should be around 10 gpm on speed 2. My storage side is around 14 on speed 3. 

Like I said it just started about a week or so ago. Could it be the warmer temps outside affecting it? We've been in the upper 30s to low 40s. 60 outside today.


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## maple1 (Feb 18, 2018)

That's weird. I was also thinking scale but the big boiler dt is a puzzler.


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## warno (Feb 18, 2018)

Is it possible the storage side is scaled up? I know they're seperate from each other so I suppose one side could load up and not the other.  I mean when I pulled a water sample for pH testing it was brownish water. No heavy sediment as nothing settled out in the sample but the water was brownish so there is something in it.

Should I pull the screen on the storage strainer just to check if it's full? If that screen is full I guarantee the HX has crap in it too.


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## maple1 (Feb 19, 2018)

Maybe the boiler side is scaled enough that it is restricting flow quite a bit on that side? The big dT could be from heat being pulled away on the other side, but it could also be from quite low flow on the boiler side. That is my first inclination, since it seems to have just started and nothing else has changed? Might not take much on that smallish HX?


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## warno (Feb 19, 2018)

maple1 said:


> Maybe the boiler side is scaled enough that it is restricting flow quite a bit on that side? The big dT could be from heat being pulled away on the other side, but it could also be from quite low flow on the boiler side. That is my first inclination, since it seems to have just started and nothing else has changed? Might not take much on that smallish HX?



After I got to thinking more about it last night I'm wondering about the boiler side as well. The higher delta t would mean reduced flow on that side. Also the faster rising boiler temps would mean reduced flow through the boiler. But what I don't understand is the boiler water looks clear enough to drink,  I'm not going to, and the strainer screen looked like the day it was installed. Is it possible enough very fine particulate finally got caught up in the HX it's causing issues? 

When I checked it yesterday evening the boiler was idling at a temperature of 192, coming down from the 195 shut down limit. The storage was in the 150s throughout. When I checked my deltas at the HX. boiler side was 192 in and 162 out. storage was 152 in and 158 out.  Huge delta on boiler side compared to storage. These temps were taking right on the HX ports again. 

So I'm thinking 3 options on the boiler side

1) HX scaling
2) impeller on circ has damage from cavitation and not flowing good enough
3)  other blockage I'm  not thinking of


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## Marshy (Feb 19, 2018)

warno said:


> After I got to thinking more about it last night I'm wondering about the boiler side as well. The higher delta t would mean reduced flow on that side. Also the faster rising boiler temps would mean reduced flow through the boiler. But what I don't understand is the boiler water looks clear enough to drink,  I'm not going to, and the strainer screen looked like the day it was installed. Is it possible enough very fine particulate finally got caught up in the HX it's causing issues?
> 
> When I checked it yesterday evening the boiler was idling at a temperature of 192, coming down from the 195 shut down limit. The storage was in the 150s throughout. When I checked my deltas at the HX. boiler side was 192 in and 162 out. storage was 152 in and 158 out.  Huge delta on boiler side compared to storage. These temps were taking right on the HX ports again.
> 
> ...


My vote is #2. 
If you speed up the boiler circ is it still cavitating like it use to? Maybe performance is dropping from damage due to cavitation.


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## warno (Feb 19, 2018)

Marshy said:


> My vote is #2.
> If you speed up the boiler circ is it still cavitating like it use to? Maybe performance is dropping from damage due to cavitation.



Oh yes cavitation is terrible at speed 3 sounds like gravel going through there. Speed 2 is bad enough. 

I would just shut it down and drain the boiler if I knew it wasn't going to freeze anymore. I'm draining my boiler water into drums to put it back in after my replumbing takes place. I can't see wasting the treated water.


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## maple1 (Feb 19, 2018)

Ya, never thought about the impeller being damaged. Which should have been the first suspect given the thread we're in.


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## warno (Feb 19, 2018)

maple1 said:


> Ya, never thought about the impeller being damaged. Which should have been the first suspect given the thread we're in.



Could it get to a point where it "all of the sudden" quits pumping enough flow? Its literally been within the last week or so that's it's been having this issue.


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## Marshy (Feb 19, 2018)

If it's been cavitating for the whole time I believe it could have caused damage to the impeller to the point where performance has dropped. The ends of the impeller get erroded and the pump moves less and less water. It's a real possibility and matches the symptoms.


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## warno (Feb 19, 2018)

I guess I'll fight through this week and maybe pull the pump this weekend and check it out. I suppose if it's beat to crap I'll shut 'er all down and drain the boiler to start replumbing. Not really what I wanted to do at this time but I can't see sending perfectly good wood up the stack in a cloud of smoke. 

I could throw a new impeller in the pump but then as soon as it starts cavitating, due to the current plumbing set up, I'm just trashing a new impeller.


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## warno (Feb 20, 2018)

I called supplyhouse.com today and they told me that they cannot get a impeller for my NRF-36. Should I try B&G directly to see if a factory direct replacement is available? 

If I can't rebuild it I'm going to need a new circ for my new plumbing setup. Should I go with a single speed pump or run another variable? Once I get to replumbing I'll have my head loss figured so sizing shouldn't be an issue.


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## leon (Feb 20, 2018)

Hello Warno,


if you go to the B+G web site they have dealer links. I am sure you can either get a new circulator and 2 impellers and new gaskets.

I was able to purchase new springs for the couplers on my single speed B+G circulators that were over 30 years old.

www.bellandgossett/sales-service/


Go to the find your local rep button and then type in your zip code and go from there and they will help you find a stocking B+G reseller.


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## warno (Mar 1, 2018)

I haven't had a chance to pull the circ apart to check on the impeller but I've been thinking about my hat dump zone. With the idea that it may never get used I've been wondering about using my current garage heating loop as the dump zone instead of a dedicated WAHX. 

I'm thinking about running a line from my diverter valve up and tie into my current heating loop.  The diverter valve only opens in the event of over heating situation.  I'm going to use the controller that controls the diverter and tie it in parallel with the garage loop pump and fan on that line. 

So if boiler is over heating, diverter valve opens, garage fan and pump kicks on. My thought is the garage pump would be in series with the storage charging pump to help with the added head of the garage loop. 

Here's my sketch of what i think the plumbing would be. Would this work for my heat dump? 








Does this make any sense? Lol


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