Wood boiler startup problem

timberframe Posted By timberframe, Oct 2, 2018 at 8:30 PM

  1. timberframe

    timberframe
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    Dec 11, 2013
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    After building my first fire of the season two nights ago, I was not getting heat inside the house to the 20 plate heat exchanger. Outside it sounded like the water pump at the wood boiler was struggling to work. So I purchased and replaced the water pump. That night everything seemed good. But tonight the new pump was squealing non stop. Any ideas? Could the 20 plate heat exchanger in the house be plugged? Thanks for your help.
     
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  2. TCaldwell

    TCaldwell
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    Oct 26, 2007
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    The plate hx should be cleaned annually, I’d do that first then purge the air from the loops on either side of the hx. Check the mfgr on the preferred cleaning method. You didn’t mistakenly partially close a isolation valve somewhere?
     
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  3. maple1

    maple1
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    Sep 15, 2011
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    It could be plugged but I'd suspect not if swapping in a different pump seemed to fix the issue once. For a while. Air? Although I don't think I would describe an airlocked or cavitating pump as 'squealing', any that I have heard.

    With some valves and some boiler drains in the right places, it is a piece of cake to flush. Just hook a couple hoses up and turn some valves and flush away. Might not be a bad idea to open things up and cut & sweat that stuff in if it's not there already - might also be useful for getting air out if needed. Maybe add some unions while at it to allow easy component swapping.

    How long has this setup been in operation? Without a HX flushing? Do you have any filters or Y-strainers? Maybe some dirt got loose from somewhere? Did you do anything else to anything else?
     
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  4. timberframe

    timberframe
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    Dec 11, 2013
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    The system was up and running for the past two winters. This is going to be the third. I have not cleaned anything. Perhaps I should put a filter in just before the pump.
     
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  5. maple1

    maple1
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    It is not overly capable but I have a regular wye strainer in front of mine. It also has isolation valves, and I swapped a valve for the plug on it so all I need to do to drain it where dirt would end up is open the valve. I have never had dirt though but there would be more chance for that with an open OWB. Could be possible you have had some rust accumulate somewhere that flaked off? Or sediment?

    So if doing that, I would definitely also cut/solder in what you would need to (ball valves, drains, unions if not present) for easy HX flushing & servicing while I had my system down. Buying ball valves can add up $-wise but definitely worth it when an issue arises.

    Did you see any traces of any dirt at all anywhere when you swapped pumps? Could still be some kind of other issue going on. But I think I would want to flush my HX anyway if it's been two full years without doing it yet. Questionable water quality can also scale up a flat plate fairly quickly.
     
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  6. peakbagger

    peakbagger
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    Worth cutting in some pressure gauges on either side of the heat exchanger and the pump. You can them estimate flow off the pump curve and then look up the pressure drop across the heat exchanger to see if its over the design pressure drop. My guess is your system is air bound. Circulator pumps are water cooled and if they are tryng to pump air they may overheat.
     
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  7. Fred61

    Fred61
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    Cooled and lubricated.
     
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  8. timberframe

    timberframe
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    Its hard to figure, Today when I turned the system back on, It ran smooth with no problem. I do think I will take you advise and add some unions and ball valves. Is the 20 plate heat exchanger on the small side? Should I step up to a 40 or 50 plate?
     
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  9. maple1

    maple1
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    I don't think anybody can say for sure without knowing about your system and what all you are heating. But 20 is pretty small. That's what I have just for my DHW.
     
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  10. warno

    warno
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    Usually a "squealing" pump is a dry pump. If you lost prime and it ran dry it would squeal for sure. Pull the heat exchanger out and check it for flow and scale build up.

    And yes 20 plate is very small. Was the system working fine in the past 2 years? I believe you said it was?
     
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  11. timberframe

    timberframe
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    Dec 11, 2013
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    The system was working well the last two years. We thought it should put out a little more heat when it was bitter cold, but overall it worked well. I ordered a 80 plate Kelvion GBE 400-80 heat exchanger yesterday. It is 5"x12" and should be big enough for the system. We run 5 zones and also a zone for the domestic hot water. Perhaps I undersized the stove for this 3500 sq ft house, but the new heat exchanger might help.
     
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  12. timberframe

    timberframe
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    Dec 11, 2013
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    I installed the new 80 plate heat exchanger. It seems to work fine. After it ran for the last four days or so, I did wake up this morning again to the squealing pump. I wonder if scale is getting to the pump and plugging the inlet.
     
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  13. Woodfarmer1

    Woodfarmer1
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    Nov 10, 2013
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    You may have, as I use a 1000gallon Garn.
     
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