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Sizing main vents

RSCRSC Member Posts: 1
What is the procedure for sizing main vents in the basement for my steam system. I see a 35, 75 and 77 in the Vent-Rite non-vacuum vents. Each has a different operating P.S.I. I had a new furnace/boiler installed to replace the one from the 1960's and the installer never checked the system and it seems to function poorly. I have read about the need to balance and will be checking the individual radiator vent sizes. Possibly the mains are too small.

Thank you, Bob


  • SteamheadSteamhead Member Posts: 11,380
    Measure each of your steam mains

    and tell us their length and diameter. We can tell you what you need. 
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    Venting suggestions

    In addition to Steamheads comments, I will suggest that you do not change the radiator vents until the main vents have been replaced.

    Slow radiator vents coupled with fast, and capacious main vents works best to fill all the supplies with steam before the steam starts up the risers to the radiators.

    Post some pictures of your boiler piping so we can see if there are any other factors here causing poor performance.--NBC
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