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Thread: Pump problem?

  1. #1

    Default Pump problem?

    My house is heated with a water boiler through baseboard heaters. The question I have, is it seems that my pump will only start when I turn it above 21 Celsius and if I ever set it lower than that it will not start no matter how cold it gets. Is there something wrong with my pump or thermostat?

    It is an older thermostat (20 years probably) and my pump is pretty old as well and leaks a bit in the summer when the boiler is not turned on. The heat when turned on seals the pump to the boiler and it doesn't leak. I know the pump will eventually need to be replaced cause of this or if it stops working.

    Want to know if anyone has seen this issue and if maybe just buying a new thermostat might fix it?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Is the thermostat set to cooling rather than heat? If it is a simple two-wire thermostat, all it does is connect the two when it needs heat.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    It is a simple two-wire thermostat and does not have a cooling feature. The problem is when it should require heat it is not triggering the pump to send hot water unless it is turned up high. I thought I should be able to have hot water running through my baseboard even when it is set lower. I just bought this house and I'm not very familiar with this kind of setup

  4. #4
    DIY Junior Member tedfrk's Avatar
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    when those old mercury t-stats get old they are not real reliable anymore id change it out for a new digital one.youll be happy you did just remamber to shut off the power before you change it out.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    Yep, sounds like the thermostat bought the big one...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    Plumber krow's Avatar
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    In most cases, the pump is wired so that when the boiler temp reaches a certain temp(anywhere between 110 -120 degrees F), it will be activated. When the boiler water temp comes down below the 110 F, it will stop circulating, giving the water in the boiler a chance to reach a desired temp, eg: 110-120.

    The pump is only directly connected to the boiler water temp, not the room temp (where the stat is)

    It all depends how your boiler is wired in relation to your pump and where the hi & low limits are set
    Last edited by krow; 10-25-2008 at 04:49 PM.

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