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opening and closing radiators for steam heating system

I have several rooms where I don't typically heat unless needed for some occasions. I can open radiators as needed without any concern for boiler water level when I turn them off again?


  • KC_JonesKC_Jones Posts: 4,369Member
    edited November 2016
    The valves typically won't seal completely. The steam still gets through in small quantities. It then condenses and as water it's "bigger" and won't drain back. This can slowly fill the radiator up and rob the boiler of water.

    Question, what do you hope to accomplish by keeping them off?

    Closing them down effectively oversizes the boiler which can lead to short cycling which isn't as efficient. Also keeping a room "unheated" puts its load (in part) on the surrounding rooms so in a sense you are still heating that room.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • MikeB001MikeB001 Posts: 14Member
    I see your point...however I was thinking since the radiators are in my garage and another in my finished attic (un-insulated) are isolated from other rooms
    BTW, i have a two pipe you are suggesting condensate/water would not drain from the trap with the valve close or mostly closed?
  • FredFred Posts: 8,282Member
    On a two pipe system, any condensate will drain back to the boiler. There is still an issue with over sizing the boiler when you close radiators off. There a good chance your boiler is already over sized, so you'll be adding to that issue.
  • KC_JonesKC_Jones Posts: 4,369Member
    Correct, I was foolishly assuming 1 pipe. My mistake on the drain back.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Jamie HallJamie Hall Posts: 12,156Member
    The only real problem which might crop up on a two pipe system -- other than increasing any short cycling, which may or may not be a problem depending on how big the rest of the system is -- may come up if one or more of those radiators are in spaces which go below freezing. As noted, it's rare for a valve to close completely on steam, and the small amount of condensate will drain -- unless it freezes in the trap (ask me how I know). It won't do any damage, most likely, but will prevent the radiator from heating when you do turn it on. Hair dryers fix the problem...
    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
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