In need of help sizing circulator for homemade boiler

[Bob Rohr]

Certainly I would add a properly sized pressure relief valve to any pressurized device. A relief valve for boilers will have both a psi and BTU rating on it. Typical residential boilers come a 30 psi relief but you can buy lower psi also.

I put a 10 psi on any of the hydrohearth fireplace heat exchangers I came across , when those were popular years ago..

And of course a pressure relief valve should be tested yearly as they can stick shut after time.

Treat anything with pressure with respect boilers, air compressors, refrigeration circuits, etc.

I cringe when I see compressed air lines run with PVC pipe.

 

[kentstang]

Well I definitely won't be messing with the pressurized system. On a separate note I installed my circulating pump yesterday and got everything plumbed up. I tried running it but I think trying to run the pump on high its overworking itself and getting hot. I've got about 66° water at the pump and 155° at the boiler. I'm going to let things cool down and try again on low

 

[warno]

What pump did you end up going with?

What do you mean the pump is getting hot? With 155° water running through it the housing will feel quite warm.

In my experience the slower the pump runs the higher the delta T goes.

 

[maple1]

Not sure what the 66 & 155 means?

 

[Bob Rohr]

Wet rotors circulators will run a few degrees warmer then the water flowing through it. The motor is running in the system fluid.

So if you are pumping 155 from the boiler the pump will be hot.

Now if it sizzles when you spit on it, either it is locked up and turned into a resistance heater, or it could be airlock and not getting fluid to cool itself.

A quick easy way to determine if s circulator is flowing is to slowly close down the isolation or any valve downstream. You will hear rushing fluid as you chock down and the sound of the pump will change.

Carefully lossen the bolts on the downstream side to burp an air bubble from the pump if you suspect that.

Use care when you loosen the bolts as the water inside the pump will flash to steam if it is locked or overheated.

 

[kentstang]

Both the pump housing and motor were hot, but the water on the inlet side was only about 66°. I think I have a large amount of air trapped in the return side. I'm going to try and rework the return piping on the boiler tonight and install some way to vent the return, or tie it in with the main vent.

 

[warno]

how is your boiler vented to atmosphere? I can't see any vent from your pictures.

Also did you install the pump on the supply or return line? I'm curious if you pump was getting water at all. If the line was 66° and the boiler was 155 but the pump was still hot, I'm guessing it was running dry and overheating the motor.

 

[maple1]

Both the pump housing and motor were hot, but the water on the inlet side was only about 66°. I think I have a large amount of air trapped in the return side. I'm going to try and rework the return piping on the boiler tonight and install some way to vent the return, or tie it in with the main vent.

Ideally there would be an easy way to vent or purge the lines, built in to the install. Involving maybe a hose bib down low that you could hook a garden hose to, and a drain or bleed valve up high you could let air/water out. With isolation valves to direct the purge flow where it needs to go. Lines could be purged & filled before a pump is even started.

 

[warno]

Like maple said a easy bleed/drain system built in is ideal.

I for one like these valves. They are very handy. I've had them for 3 years now, and Not one leak. Alittle more money up front but to add in the cost of all the components individually it's worth in my mind.

 

[kentstang]

Ill try to get better pictures of the vent but all it is, is a 1" nipple coming straight off the top of the water tank. As for the pump I know it had some water to it because I broke a connection about 5' away from the return side of the coil. Then bled water through the pump and coil before reconnecting the line. I think its more or less a problem of going back uphill. A friend of mine suggested a Hoffman 79 valve on both the supply and return manifolds on the boiler itself. Thanks for all the input and time. I haven't given up on it yet, just minor delays with a homemade contraption

 

[Bob Rohr]

You may need to connect a garden hose and get a good, fast, pressure purge of the lines. The pump itself generally will not purge the air without some help at fill and start.

The pump should be mounted as low as possible on the boiler to give it some positive pressure. Pumping an open system can be a challenge.

Is the boiler located below or above the distribution?

 

[warno]

Those hoffman valves you mention look like big money. If you go with a valve like the webstone valve i linked above you can purge your whole system with a garden hose like Bob Rohr mentioned. An auto vent might be necessary but i don't know about one on each side.

 

[kentstang]

Bob the boiler is located probably about 10-15' above the heat exchanger. I burped the lines like what was suggested on the downhill side of the pump and was able to get the air out. That did the trick.. I don't ont have my aquastat or fan installed yet, but I have 105° inlet pressure and 89° on the discharge side. Hopefully tomorrow I can get the fan and aquastat mounted where I can get some hotter water and control it a little better.

 

[jwise87]

Don't worry too much, I had the same problems on my last homemade owb. I built it before I properly understood the hydronics and it only had 3/4" pex to the house. When I posted my build on another site everybody told me that it wouldn't work, but you know what, it kept my house warm. It probably wasn't as efficient as it could have been but I was very happy with it's performance. I did run a huge pump on it though, Taco 0013 it think. To get mine to bleed I would take the pressure line off and run the pump until I had water coming out and then push the pex into the fitting on the pump.

 

[kentstang]

So far I've been running the last 3 days without an aquastat and draft fan. I just have a piece of metal screwed on the door to keep the draft down. With the furnace cycling on and off, and the pump running around the clock I've kept the house at 75° at night. I haven't checked water temp at the boiler but down just before the pump I'm averaging 110° water.

Is there a water treatment and rust inhibitor that is better than others?

 

[warno]

I buy from this site. (broken link removed)

I bought their start up cleaner for both the boiler and my storage. And also run their nitrate inhibitors. It's pretty easy to use stuff with easy to understand directions.

 

[Bob Rohr]

You want to make sure the water temperature returning to the boiler is about 130F or higher or you will get condensation in the boiler and possible flue piping. You need to be above the dew point of the fuel you are burning.

Within 10- 15 minutes of firing the boiler, the return should be above dew point.

 

[kentstang]

Alright I just got my aquastat and draft fan working together now, I hope. I need to get some batteries for my multi-meter and ill start adjusting the aquastat until I get close to the 130° water temp.

 

[kentstang]

So far so good. The last few days has the outside temp. has gotten down below zero, and the boiler has kept the house at 78° degrees. Its been running about 7-8 hours at night without reloading and about 10 hours during the day with the high temps. being below 20`. For the most part I've been burning white oak that's been cut laying on the ground for 1-1/2 years.