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steam radiators not totally hot

fato4 Member Posts: 2
Our company installed a steam boiler about a year ago, and this is the problem that we are having (but I'm not totally sure there is one).  The customer says that the house heats fine, and all the radiators get hot, but not the entire radiator (all of them) gets hot.  He said that with the old radiator, the entire radiator (all of them) got hot.  It is an old house (around 1800's), and he has insulated the entire place (outside walls and all) about 5 years ago.  The basement piping is insulated, and he has the correct radiator vents (with the tongue) installed.  The pressuretrol was operating at 2 in and 3 out, so I cranked it all the way down (I personally did not do the install on this boiler).  The near boiler piping appears to be done correctly, but I do not see any main vents on the ends of the mains even though they are not very long.  Customer says that the system does not make any noise, and it seems to cycle properly.  The boiler has been skimmed (not by me) and the water appears to be clean.  Customer says that even when the system is operating (making steam), and he pulls a radiator vent out, no steam comes out and the entire rad still does not get hot.  The salesman did a radiator load on the house when the job was sold, but I am going to do one myself just to be sure.  It just doesn't make sense that every rad is getting hot, but not the entire radiator.  Any insight would be helpful, thanks. 


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    the whole rad

    i don't see how there could not be steam coming out, when the rad vent is removed, while the boiler is steaming. that should be the case with all the rads. the new insulation could now be so effective, that the thermostat is satisfied before all sections of the rads were filled with steam. the boiler would have to be very undersized for all the steam to have been condensed, and none left to come out the vent hole. do all the rads at least fill the same amount?

    obviously, every system needs main vents, and it's amazing that this one apparently  "heats fine". i think that people get so used to the weaknesses of their systems, that they think "it's fine". you were right to crank the system pressure down-the more down, the better, in my view. why is the home-owner pulling out the vents? is there some suspected problem he is trying to investigate?

    why not jumper the thermostat, and get up a good head of steam [8 OZ!] , and then open the vent?  if you get steam, all is well, otherwise, the system is condensing all the steam, and none is left to escape.

     definitely, get some main vents for this system.--nbc
  • MosesHomes
    MosesHomes Member Posts: 7
    Radiators do not have to get completely HOT

    If you read Don's Books you will see that the boiler is now operating correctly. Once the desired temperature is reached the boiler will shut off even if the Radiators are not totally hot all the way.  If you raise the thermostat and the boiler runs longer you will see the entire Radiator getting hot.
  • Jamie Hall
    Jamie Hall Member Posts: 23,287
    Moses is right

    In fact, it is very rare for a radiator to get completely hot.  It may get hot all the way across the top (sometimes) or sort of diagonally hot and the rest cool -- but all hot?  Rare.  It does happen -- on a day when the system is operating at or near its maximum output.

    With regards to Nick's comment, you probably won't see steam coming out of a vent hole (by the way, steam burns: don't take a vent off and run the boiler unless you have a way to quickly close the hole -- with the steam directed away from you and away from the wall!) until the radiator is pretty well all the way hot.  Until then, the steam coming in is condensing (as it should) in the radiator.

    Otherwise, as Moses says, your system sounds like it's operating just fine.  Be happy and enjoy!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • fato4
    fato4 Member Posts: 2
    thank you

    Great advise everyone, thank you.  I thought the same about the insulation, but he said that the ins. was put in years before the boiler change and the entire rad (all of them) got hot.  I know that this is the homeowner giving me this info, so who knows if it is all correct.  The homeowner appears to be up on his system, and also knowledgeable about it, but you never know.  I did forget about the fact that the entire rad doesn't normally get all the way hot, that is a good point.  The homeowner seems to be more concerned (not that it is an issue) with the fact that the radiators heat differently with the new boiler.  I am also interested in an explanation, and I hope that his info to me is accurate and that I am not wasting yours and my time.  Thanks again for the help, and I will keep you informed if I come across anything.
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