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How to trouble shoot circulation issues for a hot water boiler

I have a residential crown cxe 5 boiler with a grundfos type up pump. I am getting inconsistent heating. I suspect that there is a circulation problem because when a thermostat calls for heat, the boiler comes on, but shuts off prematurely. On shut-off, the water temp is about 200 F, which I think is the limit temperature. The pump and pipes sometimes feel like water is circulating and sometimes not. How do I remove the cover plate on the pump to see it it is turning? Any other thing to check would also be appreciated. Thanks


  • lchmb
    lchmb Member Posts: 2,997
    You would need a meter to verify the unit is getting power. An amp meter could be handy. If you touch the body of the pump is it extremely hot? Can you feel or hear it doing anything?
  • Zman
    Zman Member Posts: 7,447
    I think those are the ones with the cap on the end that takes a large slotted screwdriver. If you pull the cap, you can see the end of the shaft.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Henry
    Henry Member Posts: 996
    The only reliable method to check motor rotation on a Grundfos pump, is with this tool.
  • chrismccowan81
    chrismccowan81 Member Posts: 3
    Thanks guys! Not sure how to attach a comment to a specific reply, but to ICHMB, yes sometime I hear or feel the pump moving liquid, sometimes not. The pump get to be the temperature of the hot pipes, but not hotter.
    To Zman, the instructions with a new pump I have say to remove the cover and use a screw driver to turn the pump...but don't say how to remove the cap. I'm afraid to damage the cover.
    To Henry, that is really cool. I will check to see If I can get one of those tools.

    I have an extra pump I can put in, maybe I will. But Im thinking that maybe it is a controller that is causing the problem. If the one board with the electronic spark connection on it is the logic controller... maybe I should replace it.

    Thanks again all. Really helpful comments.
    JUGHNE Member Posts: 10,581
    The pump shown in the picture with the key ring has a large plug about the size of a nickel coin. If yours has that you can unscrew that plug. It is to bleed air out of a pump, assure that the rotor is wet and sometimes with a screwdriver, crank start a stuck pump. I remove them with the pump running and even stick my little finger in to feel the rotor spinning. If the pump is stuck then use a fair size screwdriver to rotate the rotor for starting. Water should drip out when the plug is loosened.
    The pump rotor needs water for lubrication.

    If you have a spare pump you could remove the plug on it and look inside for the slot to put the screwdriver for the "jump start". The dry pump may not rotate as easily as the wet pump will.
  • Jamie Hall
    Jamie Hall Member Posts: 21,116
    JUGHNE said:

    .... even stick my little finger in to feel the rotor spinning. ...

    Oh right. I like to live dangerously, but not that dangerously!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • chrismccowan81
    chrismccowan81 Member Posts: 3
    Jughne. Thanks. Ill try to unscrew the plug.

    As a final point, can anyone educate me on what component/board controls the pump... or how that logic works. If there is a board I can replace, maybe that next.

    Thanks again to all.