One zone not working in my heating system

Discussion in 'Boiler Forum' started by samthedog99, Mar 27, 2013.

  1. samthedog99

    samthedog99 New Member

    Mar 27, 2013
    I have a 10-year old house. I have for heating zones for my Weil-Mclain Gold CGs boiler. Two upstairs, hot water heater and the last one is the in-floor heat in the basement. This zone has a digital Wirsbo thermostat. The basement zone isn't working. The temperature has been slowly dropping in the basement. I'll try to explain what's happening when I adjust the thermostat:

    1. When I turn the temperature up on the thermostat, the icon on the thermostat display's the blinking fire icon which signifies a call for heat. In the boiler room, the Honeywell zone valve opens up, but the heat never comes on.

    2. When I turn the thermostat down below the current temperature, the call for heat icon turns off and I can hear the zone valve closing.

    The other zones seem to be working fine.

    Any thoughts? Thanks.

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Many zone valves have what is called an end switch in them that is closed when they are activated. This switch is often used to actually trigger the boiler to operate. That switch may have failed. It is pretty easy if you have a meter and can read and understand the wiring diagram. The zone valve motor may not be opening the valve fully, and that may be what is preventing it from closing the switch as well. I do not know if you can repair by replacing the defective part, or you may need to replace the whole thing (once you've isolated it to that as it could be some other failure), but I'd look there first. If the signal is getting through the end switch, depending on what you have for a controller, that could be bad. Again, it should be fairly easy to trace the 24vac control signal and find out where it stops. Since the thermostat appears to be activating the zone valve, it's probably not it.
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