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What is this?

Bob Gagnon plumbing and heating
Bob Gagnon plumbing and heating Member Posts: 1,373
edited September 2016 in Strictly Steam
This is on a dry return for two pipe steam, No F&T trap on system, is this just a vent? It's a little hard to see, but there's another pipe coming off the top of the return, tying into the top of this device. The gauge is a vacuum gauge.
Thanks, Bob Gagnon
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Comments

  • Paul S_3
    Paul S_3 Member Posts: 1,274
    vacuum breaker?
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  • Steamhead
    Steamhead Member Posts: 17,314
    That's a "float trap/air eliminator" as described in Lost Art. It looks like an early Dunham. Essentially it's a main vent for the entire system, and has a vacuum check in the top. You will probably find crossover traps connecting the ends of the steam mains to the dry returns- these vent the air from the steam mains into the dry returns. All the air exits from this device.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
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    SailahCharlie from wmass
  • Bob Gagnon plumbing and heating
    Bob Gagnon plumbing and heating Member Posts: 1,373
    edited September 2016
    Thanks for the quick reply Steamhead, the F&T device seemed to be piped different than Dan's diagram in his lost art book, does it look like it's piped properly? The ends of the steam mains, drip into a separate wet return, about a foot off the floor.
    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Steamhead
    Steamhead Member Posts: 17,314
    That's piped properly. It's not a float-and-thermostatic trap, just a glorified air vent. See page 230 of Lost Art for a diagram, and page 237 for how it fits into a system with a Return Trap.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steamhead would you leave that vent in for a new boiler install, or would you use regular main vents? Why is the Vacuum gauge there?
    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • I would say that if the crossover traps are working properly, and that if the pressure is controlled by a vaporstat set for only a few ounces, then no conventional main vent is needed.
    All the air will escape through that vent, and be prevented from reentering by the vacuum-check valve in the top. Steam will travel to the rads more quickly with less air in front of it.--NBC
  • Danny Scully
    Danny Scully Member Posts: 1,437
    Actually, in this particular case, as long as a Vaporstat is installed you could remove the device all together and install proper main venting. If you felt so inclined to leave the device, you would still want to add proper main venting.
  • Jamie Hall
    Jamie Hall Member Posts: 24,525
    The thing about that contraption is that -- if it is working, of course -- that it does seal on a vacuum. That means that the system will continue producing some heat after the burner shuts off as it drops into vacuum. It also means that the system can get heat to the radiators somewhat more quickly when the burners fire up.

    That is providing one critical thing. That the crossover traps, which were an integral part of the working of the system, are still there and are working properly.

    If they are, and the contraption still works properly, you're home free. If they are, but the contraption is toast, put some good main vents -- as much overkill as you feel like! -- where it is. No need to go out elsewhere and add main vents. If, and only if, the crossover traps aren't working or have been removed, should you consider putting conventional main vents on at the ends of the steam mains. IMHO. And even then I would very seriously consider putting all the main venting where the contraption is, and repairing or replacing the crossovers.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Danny Scully
    Danny Scully Member Posts: 1,437
    The Dunham home heating system wasn't a vacuum system. The picture I've attached is all that is inside that device. Condensate rise causes the float to rise and seal. The main downside to leaving it would be its 3/8 vent tapping. Greater venting could be achieved with either the existing 1/2" inlet or 3/4" outlet connections.
  • I think the vacuum gauge shows that at one time there would have been a disk inside the top air exit fitting to act as a check valve, and maybe it is missing. Maybe it was removed when one or more crossover traps stuck open, or an oversized boiler was installed:
    See page 62 of this for a picture of the vacuum check:

    https://heatinghelp.com/assets/documents/dunham.pdf
    --NBC
    Bob Gagnon plumbing and heating
  • Sailah
    Sailah Member Posts: 826
    I looked through all my old Dunham catalogs and can't find that air eliminator. I have lots of Sarco, Hoffman air eliminators here though. We even have a donkey cart full of NOS. I'll take one apart and post the pics.
    Peter Owens
    SteamIQ
    Bob Gagnon plumbing and heating