System design advice

[ErikAkia]

Hello all,
First let me say that like a lot of others I wish that I had found this forum a year ago.
I have been reading a great deal here for the past couple weeks.
I am running out of time. I need to start installing the system so that I can move in.

I have already purchased the wood boiler and craned it into the room. The SS tank is in place. Most of the non O2 barrier radiant tubing has been set but I have not hooked up the manifolds (yes I know I should have used O2 barrier pipe but what is done is done).
I have had the heat load for the house calculated at 66K BTU.
I want to use the wood as the primary heat but be able to switch to propane if I leave and to heat the DH during the summer.

In the future I will be adding a 8K gallon swimming pool, hot tub, 8 solar HW panels, 1200 sq' shop 120' from house.

I live 4 miles from the grid and so I rely on Solar photovoltaic. I have to be very conscious of my power usage but should have enough.
I transport my domestic water and will store it in a 2K gallon cistern.
I am planning on building my own controller.
I think that covers the basics.

I have included a drawing I would love some input on.

I realize that a primary/secondary system provides more control but I worry about the extra power needed for the additional pumps.

Thanks
Erik

 

[bigburner]

A & B looked transposed

 

[ErikAkia]

You are correct on the reversal.

You asked for more math info. This is a link for a PDF file that was given to me by the guy that did the calculations.
www.erikakia.com/RH1114forDL.pdf

It is about 4 meg. I hope it has what you need.

Thanks
Erik

 

[bigburner]

Ya used to do it this way when Wirsbo was about all you could buy, nice picture with all the spec's. It's a nice starting point, but now we just keep the loops to 300 ft +/- and use as many rolls as it takes, I know this sounds a little unprofessional, but you can't put in to much and as long as you keep your spacing tighter for rooms with lots of windows and a little less for rooms with out. Picking a home for the manifolds is as important as any thing for ease of install. Here, we always have A/C and add another HW coil in the air handler for a second stage, wind [air infiltration} would be my concern on a mountain. Nice PDF anyway, Looks like a interesting home - please post some progress pictures

 

[jebatty]

Ambitious! A pressure storage tank rated at 12psi is insufficient, IMO. I assume the Biomass 40 specs a 30psi pressure relief valve. You likely need a minimum of 12psi, maybe more, to provide pressure for your circ. You certainly don't want catastrophic failure of your tank when it is filled, let alone filled with 180F+ water. I am going to assume again that the tank should be rated at about 60psi and fitted with a 30psi pressure relief system.

 

[Hunderliggur]

Good information. I am downloading the file now, but on HughesNet it takes a while! What do you have for internet at the new house? I may switch to Virgin Mobile 3G at $40/mo.

Anyway, your goals are similar to mine.

"I live 4 miles from the grid and so I rely on Solar photovoltaic. I have to be very conscious of my power usage but should have enough." : We had to pay our utility $15K and cut down 1/4 mile x 15 feet of trees to get A/C. I wanted to put he money to panels but my better half thought it would never be cheaper to get the utility option. She won. The panels will come later.

"I transport my domestic water and will store it in a 2K gallon cistern." : We have a 1500 gallon cistern filled by a high efficiency 110VAC pump which gravity feeds to a Grundfos constant pressure pump (two actually, for redundancy and the occasional filling of a 100 gallon animal trough). While we were building (and living in trailers) I transposted 125 gallons at a time. No fun.

I used a radiant design by the Radiant Company. Not to start a religous war, but we run the make up cold water through the radiant before domestic use. The radiant water is potable (all bronze or SS circulators). The makup through the radiant moderates the peak heat load. Works fine for us. Since you are on a power budget I can't see the justification of the hot water point of use circulator. Lots of power. I also don't see the need (or reason) for the DHW storage tank. I have attached my drawing (which works). The storage is non-potable closed system with the boiler. The radiant is potable.

Looking at your drawing, it is a neat house. Tell you what, I'll come out this winter and take a look ;-) (I am a ski instructor for people with disabilities and can use a trip to Colorado).

From what you have said, all of the tubing is in and I guess you are set on the specific zones and manifold. We have about 3500SF and 3 zones. 4 would have been better, but with balancing it works fine. I guess you will be buying a lot of TACO EBV's for zone control. I run 2100F of 7/8" PEX in each zone with a dedicated circulator for each zone. You may want to consider the Taco "00-VS" setpoint circulator ($700, 4 week lead time) to keep a constant temp and flow in the system (or similar arrangement). You will not alway be needing to push 14GPM. Take a look at the Taco spec sheets for configuration ideas.

In my design I get by with a single mixing valve on the heating side, you have three in your arrangement.

I'll be glad you give you more 2 cents worth if you want. My install pics are at https://www.hearth.com/econtent/index.php/forums/viewthread/63929/

You are on your way!

 

[ErikAkia]

We had to pay our utility $15K and cut down 1/4 mile x 15 feet of trees to get A/C. I wanted to put he money to panels but my better half thought it would never be cheaper to get the utility option. She won. The panels will come later.

After all is said and done I will have about $60K into my solar electric system but it was far cheaper than trenching a line 4 miles (neighbor would demand burial for easement) plus I really like not being dependent on the grid.

We have a 1500 gallon cistern filled by a high efficiency 110VAC pump which gravity feeds to a Grundfos constant pressure pump (two actually, for redundancy and the occasional filling of a 100 gallon animal trough). While we were building (and living in trailers) I transposted 125 gallons at a time. No fun.

What model pump is that? I was thinking of going with 48V DC since they are more efficient and I already have the power. I need to fire sprinkler the house and think I can have a more reliable system if the power is coming straight from the batteries.

I used a radiant design by the Radiant Company. Not to start a religous war, but we run the make up cold water through the radiant before domestic use. The radiant water is potable (all bronze or SS circulators). The makup through the radiant moderates the peak heat load. Works fine for us. Since you are on a power budget I can't see the justification of the hot water point of use circulator. Lots of power. I also don't see the need (or reason) for the DHW storage tank. I have attached my drawing (which works). The storage is non-potable closed system with the boiler. The radiant is potable.

I had thought about running the radiant as potable but decided that I would keep them separate. I know there is lots of discussion about it and decided that it did not matter enough to do it that way.
The reason for the hot water point of use circ is to reduce the amount of water that goes down the drain when you are waiting for the hot water to get to the faucet. I had a thermal siphon set up in the old house which worked great. I am sure it used lots more propane but not having to haul the extra water was worth it. Plus I am going to have to deal with the gray water on the other end through a evapo-transpiration system so every little reduction will help. I can not use thermal siphon here so I will probably have the circ pump on a timer to reduce power.
I have the DH storage tank there so that when (if) using propane in the summer I will not have to heat the big tank with propane. Also the less heat storage the better during the hot weather. No A/C here.

Looking at your drawing, it is a neat house. Tell you what, I'll come out this winter and take a look ;-) (I am a ski instructor for people with disabilities and can use a trip to Colorado).

LOL first I need to finish the roof and heating system then I can move in. Next Winter should work. Thanks, the design is all mine (well and the wife's).

I guess you will be buying a lot of TACO EBV's for zone control.

Yes I like the new EBV's, very efficient power users. I was thinking I would only need 5? Do you see a need for more?

You may want to consider the Taco "00-VS" setpoint circulator ($700, 4 week lead time) to keep a constant temp and flow in the system (or similar arrangement). You will not alway be needing to push 14GPM. Take a look at the Taco spec sheets for configuration ideas.

If I recall that was a Delta T Pump? I would love to do Taco but none of their motors are ECM. They have a ECM coming out this spring but I don't think I can wait. I had thought about just getting a 007 with flanges for now and then swap in the new one when it comes out. There is also some discussion on what is better the Delta P or Delta T and I am still debating it.

In my design I get by with a single mixing valve on the heating side, you have three in your arrangement.

There are 2 3-way valves that are on off types that can be turned to by pass the large storage tank and start using propane. Eventually I will add solar and may not ever need propane but for the time being I figured it would be better to have the option. I may even automate it at some point and then I can change everything from my iPhone.
I thought it would be better to not draw off more heat then needed from the big tank to try and keep the stratification. With outdoor reset and can deliver only the heat that is needed and leave the rest in the tank. At least I think that is the idea.

My install pics are at https://www.hearth.com/econtent/index.php/forums/viewthread/63929/

I will take a look.

Thanks

 

[ErikAkia]

Ambitious! A pressure storage tank rated at 12psi is insufficient, IMO. I assume the Biomass 40 specs a 30psi pressure relief valve. You likely need a minimum of 12psi, maybe more, to provide pressure for your circ. You certainly don't want catastrophic failure of your tank when it is filled, let alone filled with 180F+ water. I am going to assume again that the tank should be rated at about 60psi and fitted with a 30psi pressure relief system.

I was under the impression that 12 psi was on the low end but not out of the usual range for hydronic systems.
I did not know that circulators needed minimum system pressures to run properly. How is it listed on the spec sheets?
I would love to get a 12 psi pressure relief valve but have only found a 15psi. I found a site with a calculator for sizing the expansion tank and if I put in the right numbers a 85 encapsulated expansion tank should handle that much water.
I would hate to have to put HX on boiler side.

Thanks
Erik

 

[ErikAkia]

Ya used to do it this way when Wirsbo was about all you could buy, nice picture with all the spec's. It's a nice starting point, but now we just keep the loops to 300 ft +/- and use as many rolls as it takes, I know this sounds a little unprofessional, but you can't put in to much and as long as you keep your spacing tighter for rooms with lots of windows and a little less for rooms with out. Picking a home for the manifolds is as important as any thing for ease of install. Here, we always have A/C and add another HW coil in the air handler for a second stage, wind [air infiltration} would be my concern on a mountain. Nice PDF anyway, Looks like a interesting home - please post some progress pictures

Wind is a big problem in the winter with gusts over 100mph on occasion (I recorded one at 119 about 4 years ago). The new house is using a form of ICF's and should be fairly wind tight except the weak point of the windows. I am hoping to be able to incorporate wind speed data into my outdoor reset control.
I have been working on a time lapse video of the construction. It is not done or completely up to date but I have one at
http://vimeo.com/15847677
It is in 2 parts and is really long at about 1.5 hours which is about 540 hours real time.
Thanks
Erik

 

[Hunderliggur]

"What model pump is that? " - It is a Grundfos well pump which runs on 110VAC. Draws less than 500W at 10GPM at 160 feet. I had a Grundfos AC/DC well pump but it failed just out of warranty (go figure) and the replacement cost was not worth the DC value. The Grundfos Constant Pressure pumps are dry mounted inside (about 4 feet long by 4 inch diameter). They also sell submersible units whih could possible go directly into your cistern.

Taco has a whole line of variable speed controllers and circulators. I was looking at constant termperatue (setpoint) which mixes the hot hot fromthe heat exchanger with the coller return to reach a sepoint (say 135F). They also have Delta T for radiant in/out (normally 20F delta), etc. Check out the Taco site for the installation notes for applications.

From you diagram you had a lot of zones (more than 5), like pantry, mud room, powder room, etc. The way we built our house (wood web floor trusses) we ran the radiant under everything and heat approximately 1000SF zones. I guess each of your 5 circulators feeds a manifold which feeds the sub-zones? Where are the thermostats for control? If each subzone has a thermostat then you will have a lot more EBVs.

Did PexSupply spec the circulator(s)? I have Grundfos circulators on the Radiant and a Taco on the boiler.

I have a couple of Air400 400W wind generators to put up eventually (they came rom my old house). They would make a lot of power in the winder for you. Carbon fiber blades that "twist" at high wind speed for feathering control. I think they are called AirX now. Take a look. Probably at your site a 30 of 4 foot mast would work. DO NOT mount them to the house, they will resonate (no, I did not do that).

Interesting that the water waste is a bigger driver that the electrcity to pump it. How many KW is your solar and what are you doing to storage?

BTW - my utility feed is underground about 2000 feet to my own green box transformer about 150 feet from the house, and underground to the house. The 15K for the utility did not even begin to cover the crew that worked on the project for a week, and the boring crew for a day to go under the road and up the neighbor's driveway to the next transformer, which they replaced also so they could tap the primary to my house.

 

[jebatty]

I did not know that circulators needed minimum system pressures to run properly. How is it listed on the spec sheets?

This NPSH may help you understand what I am talking about. Your issue will be exacerbated by your high elevation, which further lowers the boiling point of water.

Also, 12psi will be the low point static pressure of a 30' column of water at sea level. You need minimum pressure greater than that needed to keep your system filled at its high point.

 

[ewdudley]

I did not know that circulators needed minimum system pressures to run properly. How is it listed on the spec sheets?

This NPSH may help you understand what I am talking about. Your issue will be exacerbated by your high elevation, which further lowers the boiling point of water.

The elevation lowers the boiling point for cooking spaghetti on the stove top, but it does not affect the boiling point inside the system, which has its own pressure. However if the system pressure is measured with a gauge that is referenced to local atmospheric pressure then atmospheric pressure must be take into account to know what the system pressure really is. You just need to know what type of gauge you're dealing with, psivg (vented gauge) or psisg (sealed gauge).

Also, 12psi will be the low point static pressure of a 30' column of water at sea level. You need minimum pressure greater than that needed to keep your system filled at its high point.

Static water column pressure plus at least three or four psi is the rule of thumb, which serves to prevent sucking air into the system anywhere. One foot static water column equals 0.4335275 psi, so for 30 ft of water it comes out to 16 or 17 psivg measured at the lowest point in the system, or 3 or 4 psivg measured at the highest point in the system.

This is the minimum system pressure. A higher pressure may be needed according to the needs of the pump as the article discusses.

--ewd

 

[ErikAkia]

I did not know that circulators needed minimum system pressures to run properly. How is it listed on the spec sheets?

This NPSH may help you understand what I am talking about. Your issue will be exacerbated by your high elevation, which further lowers the boiling point of water.

The elevation lowers the boiling point for cooking spaghetti on the stove top, but it does not affect the boiling point inside the system, which has its own pressure. However if the system pressure is measured with a gauge that is referenced to local atmospheric pressure then atmospheric pressure must be take into account to know what the system pressure really is. You just need to know what type of gauge you're dealing with, psivg (vented gauge) or psisg (sealed gauge).

Also, 12psi will be the low point static pressure of a 30' column of water at sea level. You need minimum pressure greater than that needed to keep your system filled at its high point.

Static water column pressure plus at least three or four psi is the rule of thumb, which serves to prevent sucking air into the system anywhere. One foot static water column equals 0.4335275 psi, so for 30 ft of water it comes out to 16 or 17 psivg measured at the lowest point in the system, or 3 or 4 psivg measured at the highest point in the system.

This is the minimum system pressure. A higher pressure may be needed according to the needs of the pump as the article discusses.

--ewd

That article was a great read. It made a lot of sense and I will need to see if I can work out the math on my system.
I have a few question about pressures. When a tank is rated at a certain pressure, does it matter what elevation you are at? Do you have to derate the psi limit when you go up in altitude?
Also in a closed system I get the idea that you can have different pressure depending on what the system is doing. It would seem that this is more dependent on the liquid moving. When everything is static and no pumping going on is there more pressure at the bottom of the tank or even in the lowest pipe run, because of the weight of the water? If this is the case then if I put a 12 psi pressure relief valve at the top of the tank then the bottom of the tank could get over the limit?


In my case the tank is 5 feet tall and the bottom is about 6 inches above the boiler inlet. I take my return off the bottom of the tank. (So there is more pressure available at the circ pump?)
There is no other taps off the tank that have a direct connection i.e. are at tank pressure, since the loads and solar input is done through sealed copper pipe heat exchangers that can have a higher pressure. So the over all height of the water at the tank pressure is only about 6 feet.
I think that the circ may not even be needed after the boiler gets hot since I think it will have a good thermal siphon.
Does that sound better?

Thanks
Erik

 

[ErikAkia]

"What model pump is that? " - It is a Grundfos well pump which runs on 110VAC. Draws less than 500W at 10GPM at 160 feet. I had a Grundfos AC/DC well pump but it failed just out of warranty (go figure) and the replacement cost was not worth the DC value. The Grundfos Constant Pressure pumps are dry mounted inside (about 4 feet long by 4 inch diameter). They also sell submersible units whih could possible go directly into your cistern.

My sistern is a 2000 gallon PE tank in the utility room. The house is built on tombstone granite and I did not want to try and blast a area for the tank. I will likely go with a Sun Pump 48V Centrifugal Surface Pump.

From you diagram you had a lot of zones (more than 5), like pantry, mud room, powder room, etc. The way we built our house (wood web floor trusses) we ran the radiant under everything and heat approximately 1000SF zones. I guess each of your 5 circulators feeds a manifold which feeds the sub-zones? Where are the thermostats for control? If each subzone has a thermostat then you will have a lot more EBVs.

Yes, I am only planning on zoning each manifold so when the thermostat that is in the area of each manifold calls for heat then the entire area that comes off that manifold gets hot water. I tried to divide the house into common areas that would all like to be at the same temperature and pipe them all together. I figured that if one room is constantly hotter than another I can adjust the balance valve on the manifold to reduce heat input for that area.

Did PexSupply spec the circulator(s)? I have Grundfos circulators on the Radiant and a Taco on the boiler.

They did, a Taco 0011. I would rather do some kind of variable speed instead to try and reduce the chance of noise and power use.

I have a couple of Air400 400W wind generators to put up eventually (they came rom my old house). They would make a lot of power in the winder for you. Carbon fiber blades that "twist" at high wind speed for feathering control. I think they are called AirX now. Take a look. Probably at your site a 30 of 4 foot mast would work. DO NOT mount them to the house, they will resonate (no, I did not do that).

I had one of these I got off craigslist but did not manage to get it installed before it burned up in the shop. From most of what I have read they are not very efficient but if the price is right then why not try? I will eventually build an axialflux turbine to harvest the wind. I have to be careful since the gusts are so high.

Interesting that the water waste is a bigger driver that the electricity to pump it. How many KW is your solar and what are you doing to storage?

I was thinking about it today and think there may be a way to make it thermal siphon and if it does not work I can always use the pump.
I have 6K watts of panels and 4 large forklift sized batteries that have a total of 1600amp hours at 48 volts.



Thanks
Erik

 

[ewdudley]

That article was a great read. It made a lot of sense and I will need to see if I can work out the math on my system.
I have a few question about pressures. When a tank is rated at a certain pressure, does it matter what elevation you are at? Do you have to derate the psi limit when you go up in altitude?

Normally pressure tanks have high enough pressure limits that altitude is not taken into consideration, but strictly speaking the pressure rating for the vessel would be the difference between inside pressure and outside pressure and altitude and hurricanes do make a difference.

So, for instance, if your tire pressure read exactly 35.0 psivg in Boston; after driving to Denver, and assuming no loss of air in the tire, and assuming the tire doesn't stretch appreciably, and assuming the same tire temperature, and assuming comparable weather conditions barometric-pressure-wise, your tire pressure gauge would read about 37.7 psivg. This is because a tire gauge is a vented gauge that measures the difference in pressure between the ambient atmospheric pressure and the pressure inside the tire, and there is less pressure outside the tire at higher altitude.

So if your tank is rated for 12 psivg, then as you go up in altitude you have to have less and less pressure inside the tank to maintain a constant 12 psi difference with the pressure outside the tank.

But the good news is that for the purposes of maintaining enough pressure to insure that air cannot be sucked into your system, all that matters is the difference between the pressure inside and the pressure outside. So although to stay within the rating of the tank you may not be allowed as much absolute pressure inside the tank, you need less absolute pressure by the same amount.

Also in a closed system I get the idea that you can have different pressure depending on what the system is doing. It would seem that this is more dependent on the liquid moving. When everything is static and no pumping going on is there more pressure at the bottom of the tank or even in the lowest pipe run, because of the weight of the water?

Of course there is more pressure at the bottom. When you shoot holes in a 55 gallon drum full of water the holes near the bottom squirt out farther than the holes near the top.

If this is the case then if I put a 12 psi pressure relief valve at the top of the tank then the bottom of the tank could get over the limit?

Depends how the limit is specified; at the top or at the bottom? In any case it would have to be one candy-assed tank manufacturer for them to be quibbling about a two psi difference between the top and the bottom of the tank.

In my case the tank is 5 feet tall and the bottom is about 6 inches above the boiler inlet. I take my return off the bottom of the tank. (So there is more pressure available at the circ pump?)

The lower the pump the higher the anti-cavitation pressure it will see. Can't hurt, but if you run the numbers in the Seigenthaler article above I think you'll find that once you've satisfied the need-three-psivg-minimum-system-pressure-at-the-highest-point-in-the-system rule, then the need-high-enough-pressure-to-prevent-cavitation constraint is already satisfied.

I think that the circ may not even be needed after the boiler gets hot since I think it will have a good thermal siphon.

But then how does the thermostatic mixing valve behave? Maybe I'm not seeing it but I don't see how the hot water leaving the boiler would be inspired to circulate back down to the mixing valve.

But back to beginning, where does the 12 psi tank rating come from? Is the tank manufactured as a hydronic heat storage tank? Did you try filling it with water outside and gradually go past the tank rating to see if it seemed distressed or distorted? It just seems so odd that there could be such a thing as a tank that was engineered with so sharp a pencil that it could be rated for such a low pressure.

Cheers --ewd