Wood Boiler Coolant Circulation

[stick]

I know a guy with an outdoor wood boiler, and he is not getting coolant circulation. The pump in the house is running, the wood boiler is stoked, but the pipes aren't warming up.

He has tied the system to the house water system to utilize the house water pressure to push water back out to the wood stove to test for any plugged lines. He got flow out at the boiler. He changed the pump a while ago and is going to try a new pump soon.

Any thoughts/comments/suggestions?

Thanks in advance for any input.

[JumpStart73]

could be a busted line underground. i put in a hot water coil on a furnace once and the guy i put it in for was going to bury the waterlines himself to save money. when i fired up the pump nothing was circulating. after alot of looking and digging found the supply line was severed, so it was sucking air and not delivering water to the pump...

[jerkbait]

Another thought is if he changed something in the system like a pump. Sometimes you can get an air lock in the transfer lines. This happened to me last winter.

[haleysgold]

It sounds like the line is air locked. If there's ANY air in the line the pump doesn't have the ability to push it thru.

When you purge the lines, be sure to purge both lines. There should be 1 coming into the house and 1 going out...actually they're the same line. I hook up a garden hose to a bleeder connection in the line that pushes the water thru 1 way then turn a valve and push it thru the other way. You'll hear the air gurgle into the boiler when the air purges out of the line. I used soft water from the house. I'd be amazed if that's not the problem. I was shocked to see how much air was in my line when I had the same problem. Good luck.

[bgmny]

If he has flow from the house to the boiler you can eliminate a broken line. Did he test both supply and return lines from the house? One could be broken or have a restriction. You should be using air to test the lines instead of water. You will freeze a line by using straight water instead of a glycol mixture. If air in the lines is a problem, adding a automatic air vent would be a wise investment. Is there a control valve in the line? If it wasn't opening if wouldn't allow flow. They usually have a manual operation where you could open it without having power to the valve. Obvious things to check would be valves that got shut for some reason and never opened back up, pump installed the right way(will not pump against a check valve in the system), and plugged lines(a strainer in the system would be good). Having a permanent water connection from the house to a glycol system is a bad idea (and illegal). Hope this helps in some way!