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Need Help With Pressuretrol Problem

Mel_3 Member Posts: 15
I have a one pipe steam system. With some help from this forum I think I’m narrowing in on a problem I wrote about a week ago. Several years ago I replaced a mechanical tstat with a 25 volt power stealing programmable tstat and never had any problem. It’s been working great. The only time the tstat screen would go blank was if the low water cutoff switch opened and cut power to the system. I really liked that because it would alert me, upstairs, to the need to fill up.

Just recently we capped the system because we’re creating a second zone upstairs which is an entirely separate system. We had ten radiators and now we have seven on the steam system. The problem is that now a few times each day the tstat screen goes blank and the system short cycles. Later it comes back on and repeats. It’s an intermittent problem. The only other place where the circuit can open (besides the low water cut off and the switches) is the pressuretrol, I think. So I suppose the way the system used to work was that the tstat was always satisfied before a build up of pressure that could trigger the pressuretrol and open the circuit there. Do I have that right? If so perhaps someone can advise as to what adjustments should be made now so as not to satisfy the pressuretrol first. My plumbing sub-contractor (who capped the system) doesn’t have a clue. Perhaps we need a steam system expert; I’m in NE Queens, NY.




  • Gary Segal
    Gary Segal Member Posts: 37
    I'm not an expert ....

    Mel, I am not a heating contractor, so take my advice with appropriate caution ...

    It seems to me that the tstat should never lose power regardless of the state of the boiler. The power to the thermostat should not be interrupted by the operating state of the boiler, the thermostat's role is to interrupt the run circuit when the temperature reaches setpoint.

    Does the tstat have a back-up battery?

    You may want to review the tstat hook-up and just make sure everything is going to the right source.

    Good luck!

    EBEBRATT-Ed Member Posts: 15,317

    most likley now that you have disconnected some radiation the pressuretrol is causing the boiler to short cycle. Have a professional check the boiler to see if it can be down fired for the smaller load. Also have stat wiring redone as it should not go blank.

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