boiler keeps energized for heat call

Options
sldamiano
sldamiano Posts: 44
in Oil Heating

I disconnected the thermostat and the two T-T on the limit control. The boiler and the circulator both keep energizing and calling for heat. I noticed the relay doesn’t engage, I don’t hear a click, and the armature doesn’t pull and magnetize, but as soon as i put the power on the boiler it engages and acts as if it would be

Comments

  • 109A_5
    109A_5 Posts: 4,607

    The relay contacts may have welded or the return spring may have failed. Some wire touching something it should not be touching.

    Boiler Make and Model, Aquastat Make and Model, pictures may help.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    HVACNUT
  • HVACNUT
    HVACNUT Posts: 7,743

    If you've got a meter you can make sure there's 24 vac at TT in the switching relay proving the thermostat circuit is open. Then check 2 to 4 on the relay (4 being hot going to the circulator?) to see if there's 120 vac. If there's is 120 vac at terminal 4 while TT is open, the relay is shorted. The old clapper had a good life.

  • sldamiano
    sldamiano Posts: 44

    Weil-McLain WTGO-3.

    I checked the TT and it was good.

    So I would need to take TT off and then check 2-4 for the 120vac

    83084D50-546E-45FE-9ACF-56779B710607.png B46A5998-40ED-4B41-85FB-0450998486D4.png D7302C69-AE94-4093-84C0-4AAD10823A25.png ECDB5D91-8A75-49DB-BA63-EDF60EEB07ED.png 57797BB7-C6AA-4869-A3C5-DA1D024E665A.png
  • Jamie Hall
    Jamie Hall Posts: 27,899

    Disconnect one of the wires on T-T at the burner control. The boiler should not fire. OK? Now reconnect that wire and go to the other end of the two wires which connect to T-T at the burner. Disconnect one of them. The burner should not fire. OK? The voltage is irrelevant.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Grallert
    Grallert Posts: 1,213

    So the relay is not pulling closed? but you hear the pump, and is the burners firing?

    Miss Hall's School service mechanic, greenhouse teacher, dog walker and designated driver

  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,842
    edited 1:37PM

    This sounds like a relay contact is welded closed. Try exercising the relay manually and electrically several times. If that doesn't solve the problem, the relay should be replaced.

    Don't purchase the same type. Get an electronic relay instead; they are less expensive.

    Hydrolevel 3150 or Honeywell L7224C which is the lowest cost

    Don't buy this Like the one you have

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • sldamiano
    sldamiano Posts: 44

    Yes the relay doesn’t pull closed. But the pump and fire burn simultaneously. I can’t breathe in here lol

  • Grallert
    Grallert Posts: 1,213
    https://forum.heatinghelp.com/discussion/comment/1907042#Comment_1907042

    This. The only way I can think of that the pump and burner will fire is if the contacts at the relay are made either in the relay itself or behind the PCB.

    Miss Hall's School service mechanic, greenhouse teacher, dog walker and designated driver

    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,842

    Note: The Honeywell L7224C, which is the lowest-cost option, cannot be configured for heat-only operation or as a cold-start boiler control. For that option, you need to use the L7224U1002.

    The Honeywell L7224C has a minimum LO (low-limit) setting of 110°F, unlike the L7224U1002, which allows the LO setting to be turned OFF.

    The L7224C is the best deal because it is probably old inventory and priced accordingly. However, if you ever want to remove the tankless coil as your hot-water source, you'll be stuck with a boiler that maintains a minimum temperature of 110°F unless you replace the control with the higher-priced L7224U1002.

    If you need more information or a deeper explanation of these differences, just ask.

    Bottom line: If you ever switch to a different hot-water source, such as a standalone water heater, you can reduce oil consumption by setting the LO limit to OFF with the L7224U1002.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

Categories