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Thermostat stuck calling heat

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maxsimon03
maxsimon03 Member Posts: 4
Hi, I have a Lochinvar boiler with a Taco ZVC406 6 zone controller with a second SR501 that runs to a separate building.  The building has two Honeywell thermostats that lead to the one zone controller.  Both thermostats are shut off and set to 60, and do not say they are heating.  However, the controller light indicates they are calling for heat, resulting in the building temp being over 90.  I tried disconnecting the red wire on the controller which shut it off.  Any help is greatly appreciated, thanks!

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  • bburd
    bburd Member Posts: 918
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    Sounds like a short circuit in the wiring between the thermostat and the zone controller. You can check this with a test meter.

    Bburd
    maxsimon03
  • Jamie Hall
    Jamie Hall Member Posts: 23,311
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    Short circuit -- or possibly a stuck relay in the controller (not the thermostat).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    maxsimon03
  • HVACNUT
    HVACNUT Member Posts: 5,841
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    The space can't be getting heat if the zone valves are closed. At least one is powered or stuck open. So it's not the wiring between the buildings.
    2 Honeywell thermostats are connected to the SR501? Is R-W (TT) in the SR501 connected to end switches for zone valves in the other building and not connected to the ZVC board?
    If so, then in the other building there's either a bad thermostat, shorted thermostat wiring powering a zone valve open, or a zone valve stuck open and closing the end switch. 
  • maxsimon03
    maxsimon03 Member Posts: 4
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    Thanks for the help!  Both zone valves are stuck open, which I’ve tested by jumping the yellow wires.  I will replace both and update.
  • maxsimon03
    maxsimon03 Member Posts: 4
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    In response to HVAC nut, the zone valve relays (red wires) are connected to the TT circuit, and the zone valve motors (yellow wires) are connected to the thermostats.