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Propane fireplace will not fire when thermo trips

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This is a strange one. I have a simple two-wire thermo controlling the fireplace, when the thermo trips and closes the circuit, the fireplace should come on. What happens is nothing, until I use a pair of pliers to short the screws on the already closed circuit. Then the fireplace comes on. When I withdraw the pliers the fireplace STAYS on. What is going on here?

Comments

  • ratio
    ratio Member Posts: 3,675
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    Contact resistance of the thermostat isn't low enough to allow the coil in the gas valve to close but can maintain it once it's closed. Check the wire terminals, then replace the stat.

    Is it a millivolt system?

    HVACNUT
  • lchmb
    lchmb Member Posts: 2,997
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    check your millivolts. If the length of run to the t-stat is longer than what manufacturer states and the thermopile get's weak it could cause this issue..
    ratio
  • ratio
    ratio Member Posts: 3,675
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    Oh yeah, a weak generator could cause that too I guess. Assuming it's a millivolt system. Can you shoot a pic of the pilot light, or the gas valve showing where the pilot assembly connects?
  • faulkner72
    faulkner72 Member Posts: 3
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    This problem has occurred no matter what stat I use so I'm assuming I have to replace something on the fireplace for it to work? I'm not at my condo currently so I can't send a picture. I'll have to wait until November when I'm back up there. The length of wire is only about 8 feet. Big question - how do I know if it is a millivolt system, and what is a millivolt system anyway?
  • ratio
    ratio Member Posts: 3,675
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    A millivolt generator uses the pilot flame to make enough electricity to actually run the whole shebang, looks like this. If the fireplace doesn't have any kind of power/batteries operating it, it's millivolt. They do fail, if you've changed thermostats I'd look at the generator next. @Tim McElwain might be able to offer more insight.
  • Tim McElwain
    Tim McElwain Member Posts: 4,628
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    What is the Make Model and Serial number? It would also help if we knew the make of the thermostat and also the gas valve along with numbers.
  • faulkner72
    faulkner72 Member Posts: 3
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    It's a FireplaceXtrordinair 35 Custom Builder. I believe the problem would be my thermopile. Either it's dirty or needs to be replaced. I've seen a number of videos on YouTube about thermopiles and thermocouples on gas fireplaces and they really look like my fireplace.