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Boiler stops running after a few hours

kiemside
kiemside Member Posts: 10
It is a gas steam boiler with a wired-in thermostat.

Everyday, it always runs first time I turn it on. But it stops running after about 2 hours.

When it runs, I use a multimeter to check and find voltage at the thermostat and between terminals C and R and between terminals C and Y at the transformer.

When it stops running, there is no voltage at the thermostat and also nothing between terminals C and Y. However, there is still voltage between terminals C and R at the transformer.

The vent damper is on always on the "open" mode.

Does anyone know what is going on?

Comments

  • JUGHNE
    JUGHNE Member Posts: 9,750
    Does your pressure switch shut it off?
    If so it should start again if the T-stat is still calling for heat.
  • Jamie Hall
    Jamie Hall Member Posts: 18,903
    JUGHNE said:

    Does your pressure switch shut it off?
    If so it should start again if the T-stat is still calling for heat.

    Or any one of several other safeties -- like a low water cutoff?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • kiemside
    kiemside Member Posts: 10
    I found the culprit. It was the pressuretrol and its pigtail pipe, which were clogged. I open them up and cleaned them. Put them back together and the boiler was running all night.

    I guess because of the deposit inside the pressuretrol and the pigtail pipe, the pressure never got back down to the cut-in pressure. As the result, the boiler doesn't turn back on after running for a few hours.