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air question

I'm looking at an old vapor system , The unit comes on , runs for 5 or so mintues , goes off briefly on low water .Water comes back to the boiler ,then for several minutes the air vent on the dry return, starts blowing air . Boiler starts and goes thru the the same scenario . Any thoughs??


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    vapor system

    these old systems need low pressures-could the pressuretrol/vaporstat be allowing more than a few ounces of pressure, and what is the pressure? check the pigtail for blockage.

    if the main vent is a hofmann 76[?], the restrictor plate under the cap may have stuck, and now no proper venting. try running the boiler briefly with the vent off [be careful, with your hand on the switch]. see if the water level does not drop. if replacement is needed, then replace other main vents at the same time with gorton #2's or multiples thereof.--nbc
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