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Honeywell Zone Control Question

Finished replacing my boiler with surprisingly few problems. The one exception being a zone control valve. I reused the three old ZCV's (Honeywell 9045's). Two are functioning properly, the third won't stay open. The problem looks to me to be something to do with the switch that shuts off power to the ZCV motor once the valve is open. What is happening is that once the valve opens all of the way it depresses the kill switch for the power to the ZCV motor. As soon as the kill switch is depressed the valve reverses to try to close. Once the kill switch is no longer depressed the valve reverses again trying to open until the kill switch is once again depressed. This will go on until I shut down the thermostat for that zone.

I don't understand how the ZCV can stay open once the kill switch is depressed.

Is there anything that I should look for or should I just replace the valve?



  • 1buddy
    1buddy Member Posts: 5

    The ZCV are 8043 F
  • Paul48
    Paul48 Member Posts: 4,470

    The power for the valve itself should not go through the "end switch". The end switch is just a set of dry contacts that work off the valve position. It is typically used to control the circulator, to prevent it from being on against a closed valve.
  • 1buddy
    1buddy Member Posts: 5
    Thanks for replying

    I ran all of the wiring for the ZCV and thermostats through a Taco control unit. Everything seems to be working as it should except for the one ZCV cycling on and off.

    I can see and hear the valve in question spinning when I turn up the thermostat on the zone . It just won't stay open. Once the contact switch on the ZCV is depressed the motor begins to spin in the opposite direction until the switch is no longer depressed then it reverses direction again to open the valve.

    I believe that the valve is designed return to the closed position when not powered up which is what is happening. There has to be something that holds the valve open when the Tstat is calling for heat after the valve has fully opened and depressed the contact switch I just don't see it.

    Wondering if there is something I have wrong that I could correct or if the valve is a goner.
  • Paul48
    Paul48 Member Posts: 4,470

    Nothing shuts the power off to the valve when open. When power is shut off to the valve, it closes. The coil that operates the valve  is energized by your Taco ZVC, and the power stays on to the valve until the zvc stops sending it. Just like a lightbulb off a switch.
  • RobG
    RobG Member Posts: 1,850
    How about?

    Try switching heads with one of the other zv's that is working correctly.

  • tangled in wires
    tangled in wires Member Posts: 23
    no power bad motor

    hey buddy.

    I assume your talking about the basic 4 wire zone valves 2 yellow  wires and 2 red wires.  its interesting that your motor is opening and closing simultaneously. Usually when the thermostat closes on a call for heat it sends power down to the motor. The motor will slowly open and stay open until power from the t-stat is cut off. Then the ZV is closed by spring tension.

    Do you have Voltage going to the motor when the t-stat is calling?  It sounds like the motor either is bad or you are not getting power because its opening and then power is dropping off and the spring is closing the valve that only should happen after the t-stat is done calling for heat.
This discussion has been closed.