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Zone Valve staying open after thermostat finishes calling for heat

mrgto455 Member Posts: 3
Hi all, hoping someone can help me. My home is heated by FHW baseboard and gas. I have 4 zones. The one zone that is giving me issues is for my living room. It doesn't happen all the time.

I have the thermostat set to 72, heat comes on then the heat stays on and CRANKS. Seems the zone is staying open and keeps pushing hot water through the pipes until I physically have to take the wires off the zone valve to shut it off.

If I leave the wires off for a while it will return to normal most times. This has happened maybe 4 or 5 times last year. I'd like to try to figure it out before I have to turn the heat on this year.

A friend of mine mentioned that maybe it the transformer. He also mentioned changing out the transformers to something simpler but not sure what that would be.

Anyone ever experience anything like this? No I have not had a chance to put a meter on the valve when this happens as I don't own one.



  • hot_rod
    hot_rod Member Posts: 21,882
    sounds like the thermostat is not turning off properly, or a shorted wire. If the valve closes when a wire is disconnected, opens when reconnected it sounds like the valve is operating correctly.

    What brand and type of valve?

    Sometimes something gets stuck in the valve/ seat mechanism keeping it open slightly, but removing wire would not fix that.

    Has the circulator pump been changed or replaced?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Don't let your 'friend' touch it. It's not the transformer. But it is a matter of a tech who knows how to use a meter to troubleshoot and isolate the problem.
    Could be any or some of the things @hot rod mentioned.
  • mrgto455
    mrgto455 Member Posts: 3
    I've switched out the thermostats because we have 4 Honeywell in the house and it still does it no matter what thermostat is installed on that zone. My guess is it is a short somewhere.

    Taco valve.

    The pump has been replaced because one of the upstairs zones wasn't getting enough heat. The pump had 25yrs of service when it was replaced. House is 26yrs old now.
    EBEBRATT-Ed Member Posts: 15,346
    we need to know the valve model #. it could be spring return two wire control or three wire floating or two position.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,538
    Is it an Energy Kinetics? :)
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • mrgto455
    mrgto455 Member Posts: 3
    On the body it sasy 571-2 It's a Taco. I can't read the tiny label on the twist off head.
  • hot_rod
    hot_rod Member Posts: 21,882
    If the pump is oversized it could be forcing flow past the valve, maybe when another zone is calling? If the problem started after the pump was changes, look there.

    But if removing a wire fixes the problem, it sounds like a wiring problem. Has the valve been changed recently? Is it wired correctly?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    HVACNUT Member Posts: 5,760
    The 571 has a heat motor. Slow open/slow close.
    You'll need a meter to see if the end switch opens, 1-3, after the thermostat satisfies.

    Does the circulator run while this is going on, or is it a gravity heat rise?
    Is the living room over the boiler?

    The heads twist off. CCW and pull. Swap it out with another head. Take pics and label the wiring and turn off the power first. If the problem starts happening on the zone that was swapped with the living room, then its a bad power head and a DIY job.

    If the problem reoccures in the living room, it's a short in the thermostat wiring or a faulty valve body. Not DIY.