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heater runs continuosly

we have a CROWN gas hot water boiler that runs and continues to run once we turn on the power, even when it is above the temperature setting. we changed the wall thermostat thinking that was the problem, but it still runs continually. Weve had no problems in the past. we noticed last week that the heater was continually running even with the thermostat turned off. on the boiler is a fuse and a power switch which shuts off the electric power to the control box. When we turn on the power switch and screw in the fuse, the heater starts up and will not shut down unless we turn off the switch.
Any suggestions would be appreciated.


  • steve gates
    steve gates Member Posts: 329

    sounds like a short somewhere. mice chewed tru wire, bad switch ect. it's got a call for heat from somewhere.
  • Rich P.
    Rich P. Member Posts: 60
    is it overheating?

    Or is the combustion blower just running,
    The temperature gauge will also tell you if the boiler temp is hot or not

    Rich P
  • ALH_4
    ALH_4 Member Posts: 1,790
    Sounds like

    It may be a bad zone valve or valve operator. The boiler does shut off when it hits the high limit? If not you would have a mess on the floor when the relief valve lets go. Which model boiler do you have?

  • Steve M_2
    Steve M_2 Member Posts: 121
    might be the way it's wired

    I find a lot of boilers wired to run hot especially older ones that have a coil in for DHW. Sometimes the coils are plugged off and a water heater put in and nobody wired it to cycle only when there's a call for heat. I've seen a few newer boilers wired this way as well. Is that why the power is off for the summer? Your mechanical room prolly used to be hot in the summer huh? Get a contractor out that understands control wiring and check the wiring, I bet that's your problem.

    Steve M.
  • charlie_12
    charlie_12 Member Posts: 2
    heater runs continually

    thanks for all the responses. It turns out there was a short in the thermostat wire between floors.
    thanks again. great forum
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