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Pressure issue in two pipe steam home system

Howard_3
Howard_3 Member Posts: 5
in THE MAIN WALL
History: Replaced boiler a few years ago in my 1933 home. Had a few zones of forced hot water added as I remodeled some areas of the home. At same time main vent was leaking so it was replaced wtih a Hoffman #74.

System now takes 2-3 cycles to get to temp because pressure rises and shuts of at 3.5psi (how I have it set. Cuts back in at 1). Seems that not enough air is getting out (like the hose is too narrow or something and the pressure builds Or is it something else? What can I do so I can run things at .5 or .75 psi like I use to before the vent was replaced.

Also, when things shut down for the night, after a while the vent make a lot of noise as air is getting sucked back in to the system. Is this normal? How can I stop it?

I have been using a heating contractor I like a lot but they scratch their heads a lot when I address these issues. Help[ with this matter would be greatlly appreciated.

Howard

Comments

  • FITTER-1
    FITTER-1 Member Posts: 5


    TRY TURNING PRESSURETROL DOWN.
  • scrook_2
    scrook_2 Member Posts: 610
    1.5 psi cut out...

    2 psi max, and about 0.5 psi cut in and the vent's (Hoffman #75 main?) will work a lot better. If the main's big and/or long look at Gorton #2 instead or several Hoffman #75's or Gorton #1's on a tee or tee's to vent faster.
  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    A 74 main vent is probably way too small

    All of the system air goes out that vent,unless you have some vents on the steam mains too. If you give the guys here a bit of info, such as the size of the system, types of rads,length of steam mains, boiler output, a better vent size can be figured out.

    Boilerpro
  • Steamhead
    Steamhead Member Posts: 17,499
    Right on, BP

    that #74 is way too small for a system like this. It's designed for higher-pressure unit heaters so it has a very small vent port.

    Howard, measure the length and pipe diameter (outside diameter is OK) of your steam main or mains, and we'll tell you what vent to get.

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  • Howard_3
    Howard_3 Member Posts: 5
    Pressure issue in two pipe steam home system

    Thanks for your response. I had been and still am running the system at .5-1 psi. I have to have the cut out at 3.5 however because of the pressure issue I am raising here. Otherwise the system short cycles even more.

    Others also responded and they seem to feel the vent is way too small. I'll keep you posted and if you can think of anything else, I'd appreciate it.

  • Howard_3
    Howard_3 Member Posts: 5
    pressure issue

    It's running at about 1 psi. Have it set to cut out at 3.5 or the system short cycles too much. That's what I want to find a solution to. People have suggested the main vent is too small and are offering to help me figure out how to get the right one. Thanks!!!
  • Howard_3
    Howard_3 Member Posts: 5
    pressure issue

    Thanks for responding. Gave you wrong info. The vent is Hoffman #75 main vent air valve not 74. Will send other info shortly. Also found old info on the vent that I replaced. Best I can make out it said - #40 therm flex vent-trap. The new boiler is a Burnham IN 7 which my new heating contractor says is oversized for what we need. The houses living area is 2100 sq ft. and as I said we have tapped into the boiler for 3 hot water zones. Length of piping and diameter to follow shorlty.

    Also mentioed about air getting sucked back into the system at times after the boiler has shut down for a while. It makes a lot of noise as the vent has something inside it that rattles a lot. Is this sucking of air back into the system normal???

    Howard
  • Howard_3
    Howard_3 Member Posts: 5
    Pressure issue in two pipe steam home system

    Thanks for responding. Gave you wrong info. The vent is Hoffman #75 main vent air valve not 74. Will send
    other info shortly. Also found old info on the vent that I replaced. Best I can make out it said - #40 therm flex
    vent-trap. The new boiler is a Burnham IN 7 which my new heating contractor says is oversized for what we
    need. The houses living area is 2100 sq ft. and as I said we have tapped into the boiler for 3 hot water zones.
    Length of piping and diameter to follow shorlty. I also replace all the traps (one for each convector)myself and
    the contractor is concerned that I may not have done it correctly or that one may not be functioning correctly.

    Also mentioed about air getting sucked back into the system at times after the boiler has shut down for a while. It
    makes a lot of noise as the vent has something inside it that rattles a lot. Is this sucking of air back into the
    system normal???

    Howard
  • Steamhead
    Steamhead Member Posts: 17,499
    The #75

    is better than the #74 but still may be too small. I'll know for sure when I see the specs on your steam mains.

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