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Steam stopped circulating; resetting boiler fixed immediately

Hello everyone,

I just bought an old two-unit building with two steam boilers. One of them just had an odd problem.

I noticed that the thermostat was calling for heat for about 9 hours straight, but the temperature was still dropping. There is also a hot water baseboard that feeds off that same boiler, and it had been running the whole time. So one room with that baseboard was very warm, but every other room has stream radiators and they were all cold.

I went down into the basement, and the boiler was cycling on and off every so often. The steam pipes were all cold.

Not knowing what else to do, I shut off power to the boiler and turned it back on. Within minutes, steam started circulating. The pipes and then the radiators got hot within the usual amount of time.

My question is, what should I be looking for here? Is there some kind of controlled valve that releases the steam from the boiler into the piping system?


  • mattmia2
    mattmia2 Member Posts: 4,008
    What thermostat controls the steam side?

    When the hot water zone calls for heat, the thermostat causes the boiler to be controlled by an auqastat controlled by the temp of the boiler water. It shuts the boiler off begore it gets hot enough to produce steam but hot enough to heat with hot water if only the hot water is calling.

    when the steam thermostat calls, it controls the boiler based on a pressure control, it will heat until the water boils and the pressuretrol will shut off the boiler of the boiler produces more steam than the system can consume and it builds pressure. One way or another this part of the system isn't controlling the boiler, either a thermostat problem or a problem with the pressuretrol or a relay or something like that.

    Is this gas or oil?
  • Jamie Hall
    Jamie Hall Member Posts: 17,165
    There aren't that many controls. Was the steam thermostat actually calling? Was the pressuretrol stuck? One can assume the water level was OK, since the LWCO should have shut off the boiler completely if it was low.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • brettiegabber
    brettiegabber Member Posts: 3
    Water level is good (level is near middle glass tube on side of boiler). One thermostat controls both the steam and this single hot water baseboard zone. The thermostat was calling and must have been received, because the hot water baseboard was circulating. It is a gas boiler.

    I am just now learning via Google what a pressuretrol. I don't know if it is stuck or if it would cause this exact symptom.
    EBEBRATT-Ed Member Posts: 10,374
    We are all assuming their is not a control valve on the steam line. In a two unit building and with a hot water zone

    Who knows?

    @brettiegabber can you post some pictures of the boiler the piping around the boiler and the controls
  • brettiegabber
    brettiegabber Member Posts: 3
    I won't be back until after Thanksgiving, but I will post some pictures when I get home this weekend.

    And yeah, I don't think everything in this system will have been constructed ideally, so it is good to not assume things are as someone might expect. I bet you'll all immediately spot several things wrong with it in general, because I expect the heating systems we got are a bit of a mess. We knew this home had some poor caretakers in the past so we are going through things one at a time to fix them.

  • motoguy128
    motoguy128 Member Posts: 380
    Could be as simple as contacts on a relay or contactor going bad and cycling power cycled the contacts.