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Cold Radiator

I've got a two pipe steam system with a natural gas boiler. I've been told that it used to be a coal fired vapor system, it's an old home. My problem is that I have 1 radiator that won't get hot. It only heats if I remove the bleeder cap and even that takes about 45 minutes. A contractor told me to put a Dole 1A steam valve on that radiator only but the other 10 radiators in the house have no steam valves and they work fine. Any suggestions?


  • Steamhead
    Steamhead Member Posts: 16,726
    \"Bleeder cap\"?

    Are you referring to the cap on top of a round device on the radiator's outlet piping? If so, that's a thermostatic radiator trap. If you're not sure, post a picture here and we can identify it.

    In a Vapor system, air vents thru the radiator outlets and into the overhead ("dry") return line, along with the condensate (water) from the radiator. The air is vented at a central point, and the water returns to the boiler. You may have a venting problem on the dry return, or a bad trap which might not be on the cold radiator.

    The function of a trap is to pass air and water, but close when steam reaches it. Obviously if a trap fails closed, the radiator can't vent air. But if a trap fails open, steam will get into the dry return and keep air from leaving the other radiators.

    Have you located any manufacturer's info on any of your system's components, such as radiator shutoffs, traps, or any devices piped near the boiler?

    Do you have a copy of Dan's book "The Lost Art of Steam Heating"? If not, order one on the Books and More page of this site. It's the best book I've seen on the subject, and it has a whole chapter on Vapor systems.

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