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Weil McLain 1107-1 baseboard hot water wont shut off

Multiman
Multiman Member Posts: 14
in Gas Heating

Integrated domestic hot water and baseboard hot water. Stopped responding to thermostat. Will only do constant full on baseboard hot water heat, will not cycle off. Replaced thermostat. Checked thermostat connection to furnace. Is next step replacing control board?

Comments

  • 109A_5
    109A_5 Member Posts: 2,924

    Were both the domestic hot water and the baseboard thermostat / aquastat wires disconnected at the boiler ? Does the control board seem like it is actually receiving a call for heat ? What is the actual boiler model ?

    image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • mattmia2
    mattmia2 Member Posts: 14,396

    could be a stuck end switch or zone valve too if it is using zone valves.

    109A_5
  • HVACNUT
    HVACNUT Member Posts: 7,043

    If you have the CGt, the 3 way valve could be bypassing. What model and Series boiler?

  • Multiman
    Multiman Member Posts: 14

    It is the Cgt-5pin. Series 2. Looks like it's from 2014.

  • Multiman
    Multiman Member Posts: 14

    It's only one zone, for one floor, for baseboard hot water, but it also supplies domestic hot water. It is supplying hot water just fine. The problem is that the heat won't turn off in response to the thermostat. It is running heat nonstop.

    I read on here someone else with the exact same problem on what sounded like the same unit.

  • Jamie Hall
    Jamie Hall Member Posts: 26,462

    Somewhere something is telling that boiler to run. You will need to work through the controls to find what controls what… can't tell without being there or having a pretty complete wiring diagram to work from.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Multiman
    Multiman Member Posts: 14

    So you'd say I have to do that, before jumping to replacing the control board.

  • Big Ed_4
    Big Ed_4 Member Posts: 3,288

    Post some photos of the boiler and piping .. You may have a dirty flow valve or bad check …

    There was an error rendering this rich post.

  • 109A_5
    109A_5 Member Posts: 2,924

    " So you'd say I have to do that, before jumping to replacing the control board. "

    If you want to replace the control board for $$$, you certainly can. However you run the risk of spending $$$ and replacing the control board may not repair the issue. It is your money and your choice, your gamble.

    Typically a Service Tech would want to disconnect the control wiring from the boiler (at the boiler) to prove it is actually the control board that is causing the issue. Usually isolating the control wiring from the boiler is quick and simple.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 2,924

    Looking at the wiring diagram, before I condemned the Control Module, if you have a multi-meter I'd verify there is 24 VAC between the two pins circled in Red below. 24 VAC equals no call for heat. The other way (better than just disconnecting the thermostat wires at the boiler) is unplugging the relay and the connector to the 3-way valve (Orange boxes). The thing is if the relay (pins 4 to 6) or the 3-way valve (pins 1 to 4) has a defect staying closed there could be an erroneous call for heat.

    image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System

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