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1 & 2 pipe steam system.

Disan Member Posts: 2
I’m very new to the world of steam heating and have just come  across a system that baffles me. Old three story home that was converted into a business. Used one boiler to heat all three floors and two basement radiators. Three above ground floors all have single pipe radiators but both basement radiators are the two pipe type. They also seem to not have steam traps on them and one of them looked like it had an air vent on it. System seemed to be working fine until a recent boiler replacement. Now, the system still heats for the most part but short cycles and the basement radiator with the air vent is spitting out a good amount of water from it. Thoughts?


  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    The short cycling and the water spitting are likely not related.

    With regard to the water spitting, where is the water level in the new boiler in relation to the water level in the old boiler? Particularly where there are basement radiators, the water levels must be matched, or there will be problems, and I'd want to check that first.

    Also, what pressure is the new system running, and what pressure was the old system running? Excess pressure will again cause major problems with basement radiators.

    Now for the short cycling. Is this right at the beginning of a run -- soon after steam is raised -- or is it more towards the end of a run? Very different causes.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,540
    The new boilel could be oversized, the pressure is could be too high. the boiler may not have been skimmed or piped right.
  • Steamhead
    Steamhead Member Posts: 16,842
    @Disan , where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    edited February 2022
    Sometimes basement radiators just use condensate from the upper floors, so they're piped to allow the condensate to flow through them. How full of water they are depends on how high they are and how fast they drain, but they should definitely not have any air vents on them. Make sure this isn't how these are piped.

    Regarding the short cycling, is it cycling on pressure, call for heat or does it maybe have a CycleGard?
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Disan
    Disan Member Posts: 2
    Jamie, I wasn't part of the installation team that did this boiler so I don't currently have info on the old boiler. I'll work on it though. I know the current pressure is set to 2 with a .5 differential that's subtractive.