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Steam Radiator Not Getting Hot

heatingquestionheatingquestion Posts: 1Member
edited January 2019 in Strictly Steam
My steam radiators work great throughout the house except for one. It makes clanking noises like it’s filling, but only about the first quarter of the register gets warm. The pipe leading from the basement gets hot. Thinking it was air trapped inside, I installed a new valve on the side to clear it. I can hear air escaping for about 10-15 minutes and as that happens, the rest of the register gets hot. It reaches the end, then steam escapes the vent. After the furnace turns off, the register goes cold again and the process starts over. The only thing I can think of is that the handle that adjusts the register is stripped and spins around freely, so it might be stuck in a spot that allows air to enter the register. I don’t know where to get the parts to replace that but that’s my next task. Any other thoughts on what I can do myself to solve this issue or is this a problem for the professionals? Thank you.


  • FredFred Posts: 8,201Member
    That's a bleed valve for a Hot water radiator. It shouldn't even be on there. Is the radiator tilted a little towards the trap end so that water can run out of it? It is possible the trap (At the bottom end of the radiator) is failed closed. Check that trap.
  • luketheplumberluketheplumber Posts: 38Member
    ok so someone in the past tried to fix this radiator by putting an air vent on it due to it not getting hot when they really should have rebuild the trap what you need to do is rebuild the trap and remove the vent and plug the hole BUT! before you do that be warned that rad probably has filled up with water so be prepared for that here is an article of a similar of the same problem you have
    here is how to fix it from gordy

    good luck and happy new year!
    16 years old and wants to learn about steam and hot water heating
  • Jamie HallJamie Hall Posts: 11,853Member
    That's a Hoffman Equipped system valve (almost certainly a No. 7) on the inlet -- and associated trap. Is that valve the one which you say the handle spins around freely on? That's not right at all; that valve should turn no more than about three quarters of the way around (clockwise is closed).

    If the handle spins freely -- which it certainly shouldn't -- take it off (there should be a screw on the top which you remove and just lift it off). The shaft inside should turn, but may be very difficult to turn. If steam gets into the radiator at all, though, that valve has to be at least partly open; don't go any further at this point, but please report back on what you find.

    Don't even think of replacing that valve until we can get a little farther with this.

    While you're at it, do take the nice chrome vent gizmo off and plug the hole. If the radiator will still heat at least no worse than before, the trap may be OK -- but from your description, it may not be. If so, as @luketheplumber said, the poor radiator is likely full of water right up to the inlet valve and when you do take the trap apart, you are going to get wet -- and it's not going to be nice clean water, either. Be prepared.

    Incidentally, if that the rest of the systems has valves like the one you pictured, it is actually a Hoffman Equipped vapour system, and will run best on very low pressures (no more than about half a pound per square inch) -- but we can get to that later.
    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
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,305Member
    Your steam trap is likely failed closed. Don't worry about the radiator valve until's open enough to get steam through it. make sure the radiator trap is pitched slightly with the trap on the low end.
  • GordoGordo Posts: 712Member
    @heatingquestion : Here is a shameless plug for my YouTube Channel on the poor Hoffman #18 trap which appears to be the cause of your problem radiator.

    Also, please check out my videos on restoring the excellent Hoffman #7 radiator valve.
    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.
  • Harry_6Harry_6 Posts: 98Member
    I second everything that everyone has said! And if you can get the system operating at the correct pressure (and vacuum) it's a very nice system - efficient, comfortable and economical.
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