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Is this a main line steam vent of some kind

Here are some pic's of a piece on the condensate  return line, 


    EBEBRATT-Ed Member Posts: 15,529
    You need to stand farther back so we can see. That looks like a boiler return trap. The street elbow on top is your air vent. I see some cross over traps.

    That is a vapor system. What problems are you having? You have to run that at very low pressure.

    Others that know more about vapor will comment @Jamie Hall
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    I'll comment quite happily -- when I can see more of the system. And get a better idea of what is connected to what...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,061
    Floor to ceiling shots of piping, several sides would be good.
  • Steamhead
    Steamhead Member Posts: 16,842
    edited February 2021
    Might be an air trap rather than a return trap. There may have been a check valve installed in that street 90 to hold vacuum, which worked quite well when the system was coal-fired.

    Have you found any manufacturers' info on that unit, or anything else on that system? Where is this system located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service