No Flow on Outdoor Wood Boiler System

[RZiegler]

Hello everyone, just signed up to this forum, but I've learned a lot just searching the forums. I need some help on what might be wrong with my installation. I've installed a used, 1980's vintage Jensen wood boiler rated at 100K BTUs in an existing old garage about 55 feet from our old farmhouse, which has an LP forced air system in place. All of the piping is 1". From the supply side at the top of the boiler, I have a 1" T with 1/2" valve off of it to purge air, down through a Y strainer, through a 1" flow meter then down into the pex. After entering the basement at floor joist height, I have a sidearm at my water heater, then back up to joist height to the expansion tank, which is where I've connected for make up water through a pressure limiter. Past the expansion tank is my water to air heat exchanger in the furnace plenum - 1" I/O, 9 loop 3/8" tubing, then past another valve used to purge air, back underground out to the "boiler room", where the piping comes up from floor level to enter the top of the pump, which pumps the return water into the bottom of the boiler tank. The entire distance is about 200'.
The problem is very nominal flow. I have plenty of hot water, but the H/E won't make much heat at 1GPM! Here's what I've tried:
Larger pump - I switched from a Taco 007 to a 0011, thinking maybe too much head. No difference. Then I redid the pex with 90 degree fittings at the entrance to the basement, thinking it may be kinking there when hot - same result. I tried filling with house psi water (33 psi) to force any trapped air out - same result. I really don't think that there's air in it, but what do I know! My latest idea is that the pex was kinking at the house and I've fixed that, but now I have too much pump on it?? Should I switch back to the 007 or am I totally barking up the wrong tree?
I really don't want to see the LP truck this winter, and I'm imagining a cozy 70 degrees in the drafty old farmhouse - can anyone help me?
Thanks!!
Bob

 

[leaddog]

sounds to me that you have air traped somewhere. Trapped air is hard to move sometimes. If you can close off where you have your make up water valve and back feed and then close off the other side and force feed. use as high pressure as you can.
You also might have a plugged y-strainer as you have a new system and might have moved lots of crud.
leaddog

 

[Tony H]

I am no expert but everything I have read puts the air scoop and expansion tank at the high point in the system. I once had a fan unit wired so the fan rotated in the wrong direction wonder if the pump could be done the same?

 

[RZiegler]

Guys, thanks for your responses - there was definitely crud in the boiler tank. I have cleaned the strainer several times since starting, and now I check it after every attempt and it is staying clean, but still no flow. Now that I have the flow meter, I can see the gate surge slightly indicating correct direction for the flow.

Does it seem right that the pump is pumping into the bottom of the tank? This is how it was set up when I bought the unit (used).

Thanks for the help!

 

[Nofossil]

Seems like time to start more aggressive troubleshooting. Two ideas:

1) Can you read pressures at different points in the system with the 011 running? Somewhere, there's a huge pressure drop. That's where your bubble or flow restriction is.

2) Can you plumb in a temporary (or even permanent) bypass across critical components (the heat exchanger and / or the boiler, to start with)? If you bypass something and suddenly get flow, you know where your problem is.

 

[Gooserider]

Another option that might help if one can arrange buckets or what have you just to open a line at various points and see if you can pump that far.... Messy, and you would need to be careful not to let the boiler run dry, but it might help...

Gooserider

 

[RZiegler]

Thanks for the ideas!
Right now I have my plenum heat exchanger bypassed as I'm trying to figure this out, and to keep any crud out that might be passing the Y strainer. I plan to loop the pex just after entering the house, and thereby bypass everything inside. If I get flow, I'll bypass the sidearm next. If no flow, I'll try to bypass the boiler. Does this sound like a good strategy?
And by the way, thanks for the kick in the pants!

 

[Gooserider]

Thanks for the ideas!
Right now I have my plenum heat exchanger bypassed as I'm trying to figure this out, and to keep any crud out that might be passing the Y strainer. I plan to loop the pex just after entering the house, and thereby bypass everything inside. If I get flow, I'll bypass the sidearm next. If no flow, I'll try to bypass the boiler. Does this sound like a good strategy?
And by the way, thanks for the kick in the pants!

Sounds reasonable... That should help get rid of some of the air if that is your problem, or find where the restriction is.

Another thought that might be a good thing to do in general, though it won't help with this specific issue is to consider upgrading the wye strainer - I know Caleffi makes some dirt and air separators like this listing and I would imagine other outfits probably do as well. It sounds to me like you have a certain amount of above average crud problems that are more than your wye strainer can readily cope with - something like one of these separators might do a better job of keeping the crud out of the rest of the system. This can be extra important in systems w/ plate type heat exchangers since they have narrow passages that are more easily plugged by crud deposits, and can be hard to clean.

Gooserider

 

[in hot water]

Sediment can plug tubes and pipes also. This was a common problem on the early radiant systems that used non barrier tube. Sometimes it helps to blast them out with pressure from a garden hose, just keep below the pressure relief settings or temporarily remove it.

Same for stubborn air locks, flush with well or city water pressure.

A ball valve with hose bibs on either side is a good way to make a pressure purge port. Or get a pre-assembled on like the ones used on solar installs. This can be installed anywhere in the piping to "power purge" through. Use a clear hose on the discharge to see what flows out and show you when you have a clean purge.

A typical circulator doesn't develop enough pressure to really purge a system, it's job is to just "splash" the fluid through the piping.

Some brands of boiler fill valves have a mechanism to purge at high pressure also, via a bypass lever.

hr

 

[RZiegler]

Thanks for the help and ideas - I've got flow now after purging and backflushing the system with higher pressure water. I think I had a combination of trapped air (main problem), and some crud from the used boiler in the piping. I think I'll be able to make heat with 6-7 GPM. I'll keep a close eye on the strainer, and maybe upgrade to a seperator later - this is a "low-budget" system - I just wanted to dip my toe in the water, so to speak, to see how practical wood fuelled hydronic heat will be. It's gotten a little cooler here in the last two days, but not enough for turning the heat on, although I'm kind of itching to start a fire. Maybe a test burn.....

Suddenly I'm getting ideas about more controls, water storage, seperate circuits of in-floor for a poorly insulated addition, a solar tie-in for summer hot water - is this what happens when all of the work comes together and starts working???

 

[sdrobertson]

Suddenly I'm getting ideas about more controls, water storage, seperate circuits of in-floor for a poorly insulated addition, a solar tie-in for summer hot water - is this what happens when all of the work comes together and starts working???

Oh, you haven't seen the beginning yet...this boiler and heating thing gets more addicting the longer you start tinkering. Its better than sitting in a bar (I think), I'm still looking for a 10 step program for help. My wife calls Hearth.com my "other woman".

 

[Duetech]

Thanks for the help and ideas .........I'm kind of itching to start a fire. Maybe a test burn.....

Suddenly I'm getting ideas about more controls, water storage, seperate circuits of in-floor for a poorly insulated addition, a solar tie-in for summer hot water - is this what happens when all of the work comes together and starts working???

Careful, you do all that work and you may just want to live there. That is what happens though...

 

[rowerwet]

Does it seem right that the pump is pumping into the bottom of the tank? This is how it was set up when I bought the unit (used).

Thanks for the help!

I would think you would want the pump pumping out of the bottom of the tank (head pressure) pulling through the connecting plumbing instead of pushing seems like possible cavitation issues to me.

 

[jebatty]

Suddenly I’m getting ideas about more controls, water storage, seperate circuits of in-floor for a poorly insulated addition,

If you didn't insulate first, you may be on a a long and expensive journey.