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How old is this vent?

wildrage Member Posts: 185
I pulled these off the radiators on the 3rd floor of a house I just bought. Any clue how old they are? Needless to say, I think it's safe to say it was time to replace them! Also, I purchased some Maid-o-Mist vents to replace them. Are they decent?

Old vents:

New vents:


  • Those Hoffman 40's are the best, and probably will outlast many modern ones. The oldest ones probably still work, too.
    Get plenty of main venting put on, as they do all the work.
    Put those on the lower floors, and put the maid of the mists with larger orrifices on the top floor.--NBC
  • Dave in QCA
    Dave in QCA Member Posts: 1,776
    The first vent that you have shown, the one that is older, taller, and thinner, looks like its a Hoffman #2. It is a vacuum vent and has not been in production for many years. It is a very slow vent, even slower than the Hoffman #40, and if used in combination with Hoffman #40, will allow less steam to enter by comparison. Venting rate @ 1 oz pressure for the #40 is .042 and the #2 is .016.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    JUGHNE Member Posts: 9,822
    Pulled some of those out of a 1915 church.
  • Steamhead
    Steamhead Member Posts: 15,428
    The old one looks like the original version of the Hoffman #1A. If it's a vacuum type it's called the 2A.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service