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  1. #1
    Join Date
    Jan 2013
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    4

    Default Steam radiator not fully heating

    Hi all,
    My church has a single pipe steam system for heat. We find that a number of the radiators heat only part way... about 1/3 to 1/2 of the fins. We have replaced the air vents and verified that the radiators are pitched correctly. No change. The rads are probably about 110 yrs old. What is the next thing to look at? We are thinking some sort of blockage of rust or sludge. If so, what is the remedy?
    Thanks much
    JohnNJ

  2. #2
    Join Date
    Jul 2009
    Posts
    137

    Default Re: Steam radiator not fully heating

    Yes, lack of heat in the rads could be caused by any one of several items, including clogged pipes.

    If you want to continue working on it yourself, read on---but it may be best to consult the Yellow Pages under "Heating Contractors" and get a pro in there who is familiar with steam heating systems to resolve the problem.

    First try different things with the AIR VENTS on both the rads and on the main supply pipes, as this is the easiest fix if it's all you need.

    Make sure all the supply radiator valves at the base of the rads are fully open---turned fully counterclockwise.

    1) You say you have replaced the vents on the rads, but have you also checked the vents on the main pipes???---click onto the 1st site below to view the illustration to see the main vent locations---if the MAIN VENTS (they have larger vent holes) are clogged, nearly all of the air that is in the piping system when the steam comes up, won't be expelled from the system---the smaller diameter vent holes on the rads will only partially vent the air, so the rads will heat up only partially, if at all---air vents at the rads & at the main vents come in different vent hole diameters; if the new vents you put in, as well as the main vents you have to check aren't working for you, you can always try LARGER DIAMETER vents on the rads & mains to see if this improves the heat----remember how a one-pipe steam system works: as the boiler produces the live steam, it is forced thru the main pipes leading to the rads, pushing the air that has to be expelled in front of it; if the piping, main vents & rad vents are open the steam will force out all the air ahead of it; once the hot steam hits the vents, there is a little brass alcohol-filled BELLOWS in there that is heated by the steam, expands & pushes a little needle valve into the vent hole to temporarily close the vents so that the steam can give its heat to the rads.

    Air vents can be checked for good function by immersing in a small pan of boiling water on the stove for a few minutes, then injecting air with a bike pump thru the intake---the vent should close when it's hot & open when it's cool (prevent test air passage when hot, allow test air thru when cool)---some vents can be taken apart so a lighted match can be applied directly to the bellows to close the needle valve, & open it when it cools.

    2) Check to see if the boiler water is too dirty by blowing down 1/2 gallon into a pail via the boiler drain valve----blow down should be done at least several times a week regularly; always maintain enough water in the boiler so that it is approx half way up on the glass indicator tube at the front of the boiler.

    3) Check the PITCH of the rads with a spirit level---they should be slightly pitched toward the supply pipe so the cooled condensate has a chance to drain back to the main & the boiler---if pitched the other way, use a crow bar to SLIGHTLY lift the rad on the vent end & slip a thin piece of wood or plastic under the legs to get a good backwards pitch.

    Google "One-pipe steam radiators no heat" for additional sites on this topic.




    http://www.inspectapedia.com/heat/Ra...Diagnosis2.htm
    http://www.heatinghelp.com/forum-thr...not-heating-up
    http://www.handymanwire.com/articles/steamheat.html
    Last edited by Pelton; 01-31-2013 at 01:27 PM.

  3. #3
    Join Date
    Jan 2013
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    4

    Default Re: Steam radiator not fully heating

    Thanks for your thoughts. We have checked the pitch and the inlet valve is all the way open. The radiators with the problem do get partially hot and others heat normally. Doesn't that rule out problems with the steam supply lines and the vents on those lines? The radiators in question make no noise at all. No hiss or gurgling.
    I had previously googled this question and was not able to find any info on this beyond the 'replace air vents and make sure it is pitched correctly' recommendations.

  4. #4
    Join Date
    Feb 2010
    Location
    South*East
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    1,168

    Default Re: Steam radiator not fully heating

    John it sounds like the vent you have is not venting fast enough. Try removing the vent on the radiator and see if it heats. That will tell you if you have a sludge or vent problem.

    John
    Last edited by johnjh2o; 02-01-2013 at 06:41 AM.

  5. #5
    Join Date
    Jul 2009
    Posts
    137

    Default Re: Steam radiator not fully heating

    I agree with johnjh20---I was going to suggest this as a next step; however, you have to be very careful to avoid a severe burn from a possible jet of live steam by keeping your hands away from the vent hole when trying this; always turn the boiler off when re-attaching the steam vents if steam comes out of the vent hole.

  6. #6
    Join Date
    Jan 2013
    Posts
    4

    Default Re: Steam radiator not fully heating

    I will try removing the vent, but the vents are brand new and wide open on several of the 'problem rads'.
    I'm not sure what the next step will be if this is not working. I wonder if it is possible for there to be a blockage and what to do about it.

  7. #7
    Join Date
    Jan 2013
    Posts
    4

    Default Re: Steam radiator not fully heating

    Quote Originally Posted by johnjh2o View Post
    John it sounds like the vent you have is not venting fast enough. Try removing the vent on the radiator and see if it heats. That will tell you if you have a sludge or vent problem.

    John
    Well, we removed the vent and there was no change to the rad. So I guess some sort of sludge is blocking part of the rad from getting steam. Must we remove the rad to clean it out or is there some sort of solvent that can be fed into the rad to dissolve the crud?; or is there another way?

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