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Steam radiator too hot, air vent closed

Hello all,

Great info on this site, I've learned a lot about steam heat already just by reading this forum. I live in an NYC apartment building with typical one-pipe, cast-iron radiators (just moved into this apartment).

One radiator in particular is putting out far too much heat. After reading through this forum, it seems like a thermostatic radiator valve might be the best solution. In the meantime though, I partially unscrewed the air vent (a "maid-o-mist" brand) so that it is inverted and can't release air (we just changed it and it seemed to have been functioning normally when upright). My understanding is that this should prevent steam from entering the radiator and heating it up.

The radiator is now somewhat cooler, but is clearly still getting steam; the columns close to the steam pipe are very warm, while the columns closer to the air vent are cool (I inverted the air vent two days ago). Where is the air getting out so that steam can still get in? If I replace the air vent with a thermostatic valve, will it even work as intended?


  • Upside down vent?

    My only experience is with Hoffman 40 vents, and I know they will close when upside down.

    Double check the present vent, to make sure it closes when upside down, by removing it, and blowing through it. Put a temporary plug in the hole, in case the steam comes up.

    The packing nut may be loose on the valve spindle, allowing air to come out and therefore letting steam into the rad. Possibly some nut in charge of the heating system has turned up the pressure, in a misguided effort to heat up some cold areas of the building, or he may be rewarding his employers for an insufficient Christmas bonus, by using a lot of extra fuel!--NBC
  • steamedchicago
    steamedchicago Member Posts: 72

    With the vent shut, steam can't force air out it.  but it will still compress the air in the radiator to the pressure the boiler is running at.  If, as NBC, suggests, the pressure is up high, you can still get steam in.  How much depends on what the pressure is set to, which depends, largely, on how incompetent the super is.  
  • marktheknife
    marktheknife Member Posts: 7
    Nothing doing

    I haven't removed the air vent as Nick mentioned, but I'm fairly certain it's closed when upside down. If I turn it upright, it clearly releases air and then stops when inverted again.

    I was able to tighten the packing nut slightly but that doesn't seem to have made much of a difference. It certainly seems possible that the boiler pressure is set too high, in the few interactions I've had with the super my impression is that he's fairly lazy.

    So I guess the next step would be talking to the super to find out what the boiler pressure is. >1 or 2 PSI would be considered high, from what I've read here, correct? I can certainly discuss with the management company and the co-op board if necessary. I understand that the main benefit of decreasing the pressure would be using less fuel and thus less $$. However, if the pressure was turned up because some of the apartments were too cold, what other solutions could I propose? Thanks for the help.
  • insulate the radiator?

    I used to live in an NYC apartment with radiators that overheated the place. Radiators are marvels of engineering, they are designed to be efficient -- they have lots of air space in between the sections, and they are placed a few inches away from the wall, all to assist in convection.

    But you can thwart that and keep some of the heat inside the system. Placing a solid object (that won't combust!) on top of the radiator will stop some of the air flow. And you could, if you wanted to go through the trouble, build a fiberglass jacket for the radiator (think: extra-large tea cozy) or otherwise stop heat transmission by maybe putting fiberglass behind it or in between the sections. I know one neighbor covered the exposed steam pipes in her living room with fiberglass pipe insulation, and left the radiator alone, and that reduced the temps in her apartment to tolerable levels. Just remember the black foam piping insulation will melt on steam pipes! You'd need fiberglass.

    If it were my own house, I would try the thermostatic radiator valves, but if you are just renting and don't want to/can't alter the landlord's piping, you might be able to cool the room down a little by insulating the radiator and its piping some.
  • ChrisJ
    ChrisJ Member Posts: 15,506
    edited December 2013

    If you turned the vent upside down while the radiator was filled with steam it will never stop heating.  This is why quality TRVs have vacuum breakers in them.  Even when the boiler stops producing steam the radiator will be left with a slight vacuum which pulls steam in during the next cycle.

    If you remove the vent when the radiator is cold and you know the boiler is off and then reinstall it upside down chances are the radiator will not heat.  If you unscrewed it one turn there is a chance air is leaking out via the threads.  Remove the vent, reapply Teflon tape 4-5 turns and reinstall the vent until pretty snug when upside down.  You must stop where you want as if you back up you may create a leak.  If it still does you can try using an 1/8" NPT brass plug in place of the vent. 

    If you're in an apartment with single pipe steam and are having problems like this I highly recommend the use of a TRV as you mentioned.  It will regulate your temperatures for the most part.  Make sure you buy a TRV that has a built in vacuum breaker.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • marktheknife
    marktheknife Member Posts: 7
    Boiler pressure

    I checked the boiler and it looks like the pressure is currently about 2.5 psi. I guess that's higher than what many on this site would suggest, but does that seem high enough to be forcing steam in and compressing the air in the radiator despite the air valve being inverted/closed?

    What Chris mentioned makes some sense. I can remove the valve and reinsert it so that it's tight while upside down to see whether there was air leaking around the valve that is now partially unscrewed. My only concern is that since I have no control over the boiler, isn't it risky to start unscrewing the valve and then potentially have the steam come on while the valve is off or in the process of being reapplied?
  • ChrisJ
    ChrisJ Member Posts: 15,506

    Be quick. :)

    I would assume there are times when your radiator cools down? That is the time to do it. Chances are it won't take more than 5 minutes.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • marktheknife
    marktheknife Member Posts: 7

    Ha. I'll keep that in mind. The radiator's certainly not on all the time, so it should be doable.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576

    During the off-times, air will have re-entered your radiator, so no need to "drain the vacuum".

    The best thing to do would be to talk to the management, (if you are an owner, they are employed by you). Tell them the performance of the system needs to be improved.

    When the system was first installed, it would not have behaved in this way!!!!

    It can be brought back to its original state of function, with a savings of 25-30% of fuel consumption. --NBC
  • rmoore007ri
    rmoore007ri Member Posts: 45

    Don't forget that management is always interested in saving money :-)
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Management objectives

    They don't like spending money, but they don't mind wasting it!!--NBC