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overheating zone

274 Member Posts: 2
Have a 5 zone hot water system, Honeywell zone valves, One zone in a indirect water heater. Problem is
upstairs zone over heats when thermostat is not calling for heat. When checked the problem zone valve seems to be working properly. Also tried to purge air from system, very little air at the time, but does not seem like much water pressure when trying to purge air. Not sure if zone valve is the problem?


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,257
    It's probably not closing all the way, or there is a wiring problem.
    Is it equally hot on both sides of the zone valve when the zone is not calling (or has been off for a while another zone is calling)?
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    Do you have an isolation valve on the return of the zone and a drain valve on the zone? If so you could isolate it and check if the zone valve is leaking by that way.

    I had one similar to this in a very small apartment building. They had zone valves in the ceiling of the basement. The zone valve for the zone that was overheating worked fine. But that zone had two returns from that single supply. It entered the apartment and split, and both returns ran back to the main return to the boiler. So they were getting backwards flow through those two return lines. The solution was to either add check valves on each return or to tie the returns together before they entered the main return.
    Never stop learning.
  • rick in Alaska
    rick in Alaska Member Posts: 1,429
    The actuator on a Honeywell valve is a rubber ball on a shaft that the motor turns to seal off the pipe. Sometimes the rubber ball will completely fail and disintegrate, in which case the valve does not shut off, even if the motorized head looks that way.
    See if you can feel the pipe leading away from the zone valve, (assuming it is on the supply side), and see if it feels hot with the valve off for a while. You might have to remove the ball actuator and install a new one.
  • the_donut
    the_donut Member Posts: 374
    Is this a new situation? Has something changed recently, i.e. new plumbing or eletrical?
  • HomerJSmith
    HomerJSmith Member Posts: 2,266
    Does the Honeywell zone valve have a blk terminal block or red and yellow wire coming out of it? What kind of heat emitters do you have, fin tube baseboard? What do you mean by "upstairs zone over heats"?

    When the thermostat is not calling for heat, the lever on the zone valve should be difficult to move from left to right as it moves against the springs in the zone valve. If the lever moves easily from left to right when there is no call for heat from the thermostat, it means that the zone valve is energized when it shouldn't be.

    If this is a new problem that hasn't happen in the past, then I would suspect the zone valve or wiring to the thermostat. You can check the temperature of the water entering the zone valve and check the temperature of the water exiting the zone valve several feet down stream from the zone valve when there isn't a call for heat (a cold zone). A similar temperature would indicate a leaky valve.

    I have had these valves in operation for over 20 yrs and never experienced a disintegrating ball plug, but that doesn't mean it can't happen. I have had solder balls, solder slugs, and even a large wood sliver in such cases. Something could be holding the ball open making it leaky.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,373
    I have , I have seen the balls crack and some fall apart ... That would be my first guess ... One way or the other , it needs to be pulled apart ...Maybe its just crud if your lucky ,
    I have enough experience to know , that I dont know it all
    rick in Alaska