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boiler zone valve

mike9631 Member Posts: 2
I have a 3 zone gas hot water boiler. One of the zones is for my domestic hot water. That zone is having issues. The thermostat will call for heat and open the valve but it does not always fire the boiler. It is a honeywell zone valve and I replaced the zone head thinking a bad end switch. It would work off and on. The problem went away for a few weeks and no is acting up again. Both other zones work correctly and fire the boiler when they call for heat. Just this one giving issues. Any ideas what else to check?


  • unclejohn
    unclejohn Member Posts: 1,833
    So the valve fully opens and the boiler does not start. Is the valve wired to the boiler or a control box. Pictures always help.
  • mike9631
    mike9631 Member Posts: 2
    As far as I know, it fully opens. It does work some of the time. It is wired to the boiler. All the end switches are wired in parallel and this one is the last before it goes to boiler. Sorry no pictures, I am not home at the moment.
  • unclejohn
    unclejohn Member Posts: 1,833
    Make sure all the connections are good. Sometimes with all the wires connections get iffy.
  • neilc
    neilc Member Posts: 2,709
    mike9631 said:

    , , , and this one is the last before it goes to boiler , , ,

    so that's series if they're wired one switch to the next, ("this one is the last"), and all 3 need to "make" to fire the boiler,
    and you wouldn't get domestic unless all 3 zones call.
    is it parrallel ?
    like one would think it should be,
    and any zone can fire the boiler.
    which are we?

    known to beat dead horses
  • newagedawn
    newagedawn Member Posts: 586
    sounds like a zone valve issue, especially if the aqua stat makes for the other zones
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Easily checked, diagnosed with a VOM

    There was an error rendering this rich post.

  • MikeL_2
    MikeL_2 Member Posts: 498
    If you have honeywell ZVs, I would check the ball & shaft assembly. With the power head removed, you should be able to rotate the stem easily with your thumb & forefinger......
    SuperTechrick in Alaska
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2018
    If you want to know if the zone valve is open, just move the lever on the front from left to right. If the lever moves easily it is open. If it is hard, you are pushing against the springs and the valve is not open. Could have saved you a power head. Just jump the end switch. If the boiler turns on, it is the end switch. If the boiler doesn't turn on it is the wiring between the end switch connect screws or the yellow wires and the Boiler aquastat TT connection screws. If the faulty zone valve end switch is connected to the screws on the other valve end switches, make sure the screws are tight and the wire isn't broken. If the end switches are a yellow wire all connected together with the other valves and a wire going to the boiler aquastat and connected with a wire nut, take the wire nut off and make sure all the wires are together and replace the wire nut, tightly, on the wire bundle. You should have 2 wire nuts on 2 wire bundles.

    If it is an indirect water heater, it will have a tank aquastat in a well on the tank and it will activate the zone motor and open the valve and the valve will turn on the boiler thru the end switch.

    It won't be a series connection as no valve would work if one was off. It is a parallel connection to the end switches.

    The maximum number of zone valves on a Honeywell aquastat is three.