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Help with steam main venting...

Steve_168
Steve_168 Member Posts: 39
in THE MAIN WALL
No advice?

If someone could explain the purpose and application for the Hoffman 75 vs. Hoffman 76 vent...that would be helpful!

Steve

Comments

  • Steve_168
    Steve_168 Member Posts: 39


    Hello all! I have a 1902 house with a two-pipe steam system. All of the radiators have the "Moline" valves and return pieces(the returns on the radiators are not traps). It has two mains coming from the boiler and one return line for all of the radiators. My question is, What type of vent would work best for the mains and the return? I have two Hoffman 75's and two Hoffman 76's to choose from. The 75's seems to let air in and out, while the 76's only let air out. It seems to heat the radiators faster when using the 76's, but I dont understand what effect the vacuum part of the 76 valve does! Thanks for any help!
  • BRIANJ
    BRIANJ Member Posts: 118
    Hoffman Valves

    I am also a home owner and the following is based on my experiences to date. First of all Hoffman does not recommend the 76's for Oil or Natural Gas fired systems. If you go to the Hoffman website they provide an explanation.

    Sounds like you have a two pipe Vapor system and you should be running pressure very low (6 to 8 oz) with a vaporstat.

    Gorton #2 vents are highly recommended for vapor systems for eliminating air quickly but, if your radiators are heating quickly and evenly with the 75's then you should be OK.

    If you provide the size of your mains length and diameter you may get some additional help from some of the pros on this site.

    Just my $.02.

    Brian
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    If I recall

    the Moline originally pulled the system air out with an ejector (steam-driven jet pump) then kept it from returning with a vacuum check. This was one of the few Vapor/Vacuum systems where it was OK to have steam in the dry return.

    The vacuum feature doesn't work well with oil or gas firing, since the system can go into vacuum before all the air is out. When vacuum forms, air can expand and block steam circulation.

    Steve, where are those vents located now? Steam mains, dry returns or both?

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