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radiators heat only without vent

Hello all:
I have a 1910 quasi-Victorian with single pipe steam. Most of the radiators work great, no hammer, nice heat. The boiler is 30 years old, but my plumber says it's in good shape. The pressure is less than 1psi. I also had new main vents put on (but these are 1/8" Vent-Rite adjustable valves- that doesn't seem quite right) Some vents looked original, others were cheap Home Depot ones. I replaced them with VENT-RITE #1 Adjustable STEAM AIR VALVES and most radiators work well. However, 3 radiators in different parts of the house (1st floor, 2nd floor, 3rd floor), don't heat up, even with the new vents. But if I take the vents off, the radiators all heat up just fine, and unless it's bone chilling 0 degrees, none of the radiators never get much past 2/3 - 3/4 hot. I put a new vent on these radiators no heat, no matter what I set the vent at (8 is the highest/biggest setting). The pipes are insulated in the basement with fiberglass wrapping. The radiators are all on a slight angle tilting towards the pipe. I read Dan Holohan's book, but that didn't answer this question.
Any suggestions?


  • Jamie HallJamie Hall Posts: 11,466Member
    As a first cut, can you swap the vent from a radiator which works properly -- known good -- with one from one of the radiators which doesn't work, and see what happens? It wouldn't be the first time that a vent was bad out of the box...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • papapietropapapietro Posts: 2Member
    Thanks for the quick response!
    I did try that, and the vent (on the rad that worked perfectly in the living room) did nothing for the rad in the living room that was cold. I took the vent off the rad in the master bedroom that worked well and tried it on the rad in the back room. Same thing. Vent on- no heat. Vent off = plenty of heat.
    Put the new vents on the rads that were working fine, and they continued to work fine. I've tried downward adjusting the vents in the 'hot' rooms to 1, 2, 3 etc, with no help to the cold radiators with new or old vents Take the vents off, they heat find.
  • BobCBobC Posts: 5,018Member
    Are the 3 rads that don't heat near the end of the main or are they all on one main while the other rads are on a different main? If so you may need a lot more main venting on that main.

    How long are the steam main(s) and what diameter pipe?

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • AbracadabraAbracadabra Posts: 1,948Member
    1. What's the attached EDR?
    2. What's the sq.ft. steam rating of the boiler?
  • BioBio Posts: 276Member
    Set ALL the vents at the #2 setting, wait and be patient
  • These symptoms point to inadequate main venting. Fix that and your problems will go away.--NBC
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