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WM Boiler not responding

Bowhunter74
Bowhunter74 Member Posts: 11
in Gas Heating

WM Gold CGS boiler not responding to call for heat, but will turn on when I jump the aquastat on the indirect tank. Zone valve responds to thermostat's call for heat (motor turns and engages activator switch) but it does not turn the boiler on.

What I've done:

  1. Checked that 24v are making it through everywhere. The only place I am not getting 24 is from the zone valve to the inside of the boiler.
  2. Reconnected all wires to be sure of good connections.
  3. Swapped out: thermostat, aquastat, synchro motor in zone valve.

Wondering: Could it be the activator switch in the zone valve? Should I try replacing the whole head? Would that make sense since the call for heat is activating motor, but when the internal switch is depressed, no response from boiler?

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Comments

  • Jamie Hall
    Jamie Hall Member Posts: 25,007

    At some risk of asking the obvious… what happens if you jump the control switch terminals on the zone valve? The ones connected to the boiler? If the boiler then fires… seems like the switch on the zone valve, or the motor, or not actually opening all the way…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HomerJSmith
    HomerJSmith Member Posts: 2,635

    Yes sometimes the micro switch does go bad. If you jump the end switch terminals (the top two screws on the terminal board) the boiler should fire. If so, the switch is bad. You can replace the whole head or just the micro switch.

  • Bowhunter74
    Bowhunter74 Member Posts: 11

    There are no obvious assumptions with me…I'm learning as I go.

    Can you tell me what two wires to try jumping? I've got three pairs of white/red coming in/out in addition to the pair going to the other zone valve (hot water). I also realize the top white isn't connected here—i took the pic when trying something else.

    D328C0EE-B1FC-4887-85E4-AD44C292374D_1_105_c.jpeg

  • Bowhunter74
    Bowhunter74 Member Posts: 11
    https://forum.heatinghelp.com/discussion/comment/1821402#Comment_1821402

    Any idea where I might find a replacement microswitch for this model?

  • 109A_5
    109A_5 Member Posts: 1,770
    edited November 21

    Hello Bowhunter74,

    The terminals are labeled 'End Switch' behind the wires, they connect to the micro-switch inside the zone valve assembly. In either case the switch inside the thermostat device closes (turns on) energizes the zone valve's motor, the motor turns to open the valve, when the valve is fully open the 'End Switch' closes (turns on), then the aquastat is enabled if the water is not too hot the boiler should start up. An open or defective (failed open) switch should have 24 VAC across it, a closed switch should have 0 Volts across it.

    image.png

    image.png

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Bowhunter74
    Bowhunter74 Member Posts: 11

    Jumping those two worked! So, swapping out the valve head which includes the new switch should be the solution? I assume finding the right switch to fit is nearly impossible. Thank you!

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,606

    Yes just replace the head. Supply house.com

  • 109A_5
    109A_5 Member Posts: 1,770

    Hello Bowhunter74,

    If your microswitches are the same as the ones in this video, V3-101, Digikey.com, Mouser.com and ebay.com and probably others have them. Swap the head with a new one and maybe repair the old one as a spare, up to you.

    You may also find this video interesting https://youtu.be/6C86DHujjbQ

    https://youtu.be/6C86DHujjbQ

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HomerJSmith
    HomerJSmith Member Posts: 2,635
    edited November 24

    "Any idea where I might find a replacement microswitch for this model?" A micro-switch has a rating, make and model # marked on the body of the switch. Use that as a reference. Google it.

    Try https://www.digikey.com/ or https://www.mouser.com

  • Bowhunter74
    Bowhunter74 Member Posts: 11

    Replacing the head worked. So it was that little microswitch. Thanks for the help!

  • Bowhunter74
    Bowhunter74 Member Posts: 11
    edited November 28

    Update: I replaced the head with and the system fired up and worked for several days. This morning I noticed it getting cold in the house and boiler was not turning on.

    —The new motor is humming/buzzing slightly, but the spring will not move towards the switch while the power is on and calling for heat. I can't even move it with my hand by force. If I depress the microswitch, the system fires up.

    —When the power is OFF or I do not call for heat, I can slide the spring. It is frozen only when power is supplied and calling for heat.

    Did I just get a faulty unit with a bad motor? Or is there something else that could be causing the motor to seize (of note: this was NOT the case with the old head—the motor moved the spring, but the switch wasn't working when depressed).

  • Bowhunter74
    Bowhunter74 Member Posts: 11

    Additionally: Even though I jump it, it does not open the valve so does not provide heat to the house—only the water tank. If I pop the head off, I can easily turn the valve by hand and get heat.

  • neilc
    neilc Member Posts: 2,868

    did the system work last year?

    did thermostats get changed since it worked last?

    any other changes sinse last season?

    known to beat dead horses
  • 109A_5
    109A_5 Member Posts: 1,770

    Sound like the motor (head) assembly is bad. Valve turns freely by hand, 24 VAC to the motor and it does not operate correctly.

    image.png

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Bowhunter74
    Bowhunter74 Member Posts: 11

    Nothing changed. Replaced head last week and then everything started working fine. A few days later, head will not move and activate switch. I swapped the two heads I (good one to heat, bad one to HW). The problem followed the head. New head coming. My main concern now is whether I just got a bad one, or if something caused the new one to seize up. I guess if it happens again I can go down that rabbit hole.

    109A_5

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