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Multiple Pressuretrols

Hi,
I will start by saying that I am not a Pro, just a rental owner very interested in steam and trying to educate myself. I would like to ask why larger steam boilers in multi family dwellings have multiple Pressuretrols?? Does the 2 psi. Rule still apply and do you set them all to the same pressure?

Thanks
Bob

Comments

  • Rem77
    Rem77 Member Posts: 23
    I have attached a photo of one of my boilers
  • JUGHNE
    JUGHNE Member Posts: 9,760
    edited November 2019
    Is there a 2 stage burner on this?
    The 2 outer controls are set differently....maybe hi/low fire.
    The one with the red button is a manual reset high limit, most likely required in apartment. This requires someone to visit the boiler to reset and determine why it got that high.
    The lower left one is just another pressure control set higher...
    maybe just redundant to shut off before the manual control would trip.
    I am not sure.....hope someone else has input.

    Does the mystery one say "pressuretrol" or "vaporstat"?
  • Jamie Hall
    Jamie Hall Member Posts: 18,935
    Redundancy. And, in some cases, separation of function. In your situation, I would say redundancy since you have two automatic pressuretrols and one manual reset. The manual reset one is a safety backup -- if it trips, someone has to at least pay enough attention to the system to at least vaguely wonder why. The other two may be a hi/low burner setup, or simply redundant controls. All three should be set differently, but the exact settings depend on the system. The manual one should be no more than 5 psi; the other two... well, perhaps 1.5 and 2.0 for the cutouts (note that one of them is the older, extremely reliable subtractive variety -- I'd set that at 1.5 with a 0.7psi differential, and the grey one (additive) at 1.0 cutin with a 1.0 psi differential).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Rem77
    Rem77 Member Posts: 23
    Hi
    You are correct ,it is a 2 stage burner. The 2 small ones are both Pressuretrols and one says cut in and the other says cut out. How can I figure out what to set them at?

    Thanks
    Bob
  • Jamie Hall
    Jamie Hall Member Posts: 18,935
    Rem77 said:

    Hi

    You are correct ,it is a 2 stage burner. The 2 small ones are both Pressuretrols and one says cut in and the other says cut out. How can I figure out what to set them at?



    Thanks

    Bob

    There are two styles -- and, for some reason, you have both. Don't ask...

    The grey one has on the face a pressure dial, which indicates the cutin pressure -- that is the pressure at which, if the burner has been off on pressure, it will restart (if the boiler is cold it will start anyway). Inside the case is a dial which sets the differential between the cutin and cutout -- the pressure at which the pressure switch will open and turn off the burner. The other one has two scales on the face -- the one on the right, confusingly, is the pressure at which the burner will cut off, and the one on the left is the differential which sets how much the pressure has to drop before the burner will start back up.

    Confused yet? You're not alone.

    What I don't see on your system is a low pressure gauge, which would be really helpful in setting them up. Without it, though, on a two stage, I would set it up so that whichever one of them controls the high fire range would cutout at about 1.25 psi (no, you'll not get it that accurately, but don't worry) and cut back in at about 0.5 psi. The one for low fire I would set to cutout a bit higher -- say 1.75 psi -- and cut back in around 1 psi. The idea is that on a call for heat, the burner would come on on high fire, then as the system got up to speed it would drop to low fire and hopefully stay there unless the pressure really dropped -- at which point the high fire would come back on.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Rem77
    Rem77 Member Posts: 23
    Thank you much for the info.

    Bob