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strange problem

I'm a homeowner, moderately knowledgeable about our steam heat system in our old house, but still learning.    I'm having a strange problem.  The system is building up enough pressure to be forcing air past the radiator valves (far more pressure, I think, than I want), all of the radiators are burning hot, but the system won't cut off (unless I turn the thermostat down).  Meanwhile, back at the furnace, the 15psi gauge (I know i should install a lower range gauge) hasn't budged off the pin, and the pressuretrol is already set at its lowest cut-in -- 1/2#.   So I figured both the gauge and the pressuretrol stems were probably clogged and/or busted, so I called my steam guy to come take a look.  He changed out the pressuretrol and left thinking everything was fine, but the system will still only cut off via the thermostat.    It doesn't make any sense to me that the pressure could be low in the boiler but high further up in the system -- so...stems clogged again?  Thoughts?


  • Jamie HallJamie Hall Posts: 10,653Member
    It doesn't take

    all that much pressure to get the air to zip out of a good vent, so it is possible that nothing is amiss.  On the other hand...

    Does the system ever cut off on pressure?  Say as it might be on a very long run after a setback, when all the radiators are nice and hot and the vents are closed?  If it doesn't, you may still have a clog in the pigtail to the pressuretrol (or you just might have a system where the boiler is a very good match to the radiation -- that does happen).

    A low pressure gauge is a good idea, and they aren't hard to install -- they can go, with a T, on the same pigtail as the pressuretrol.  Remember that you must keep the high pressure gauge to keep the insurance and code compliance folks happy.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Hap_HazzardHap_Hazzard Posts: 1,349Member
    edited January 2013

    Is the pigtail under the pressuretrol plugged? That's the most likely reason for a pressuretrol to be unresponsive. You should be able to blow air through it. If you can't, take it off and replace it. Also, make sure the differential on the pressuretrol is set as low as it can go.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
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