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Radiator Sizing

Robbie Member Posts: 41

I've completely read through "Lost Art", and thought I saw reference in there, but can't find it again... Simple Question is:

HOW do you size a Radiator? I am working with an 1883 Victorian which had all the radiators removed recently(before I got it). I am now in the process of replacing them: How do I figure out how much surface area is required per room? (Average room size is around 10x12 or so)

I just need an answer here- I am planning to get the other book about steam heating, but have to get radiators in ASAP, and have the opportunity to pick up more to go with the ones I already bought, and would like to see what I actually need vs. just chunking whatever into each room... I have 7, need about 4 more... So if I can figure the needs, I can tailor it a little... I need to get the radiators in within the next week or so.




  • Jamie Hall
    Jamie Hall Member Posts: 19,968
    What you need to do

    is figure out, as closely as you can, the heat loss from each room.  Not really that hard, pretty much any heat loss program can do it.  But do it room by room, not for the whole house (although as a check it's worth doing it for the whole house and adding up what you got for the room by room -- they should be close!).  And it doesn't have to be spot on; as we all know, balancing a steam system can be tricky.  But it's worth getting close.

    Then it's just a matter of matching up the output from the various available radiators to the heat loss of the room (my recollection is that 240 times the EDR is the BTU output, typically).  Again, it doesn't have to be exact -- but try and arrange it so the error is in the direction you want the room temperature to vary; that is, if you want the room a little cooler, you might be OK to go a little under on the radiator, and vice versa.

    You can, of course, go all oversize, so long as all of the radiators are oversize by about the same amount -- just means that you can handle colder temps, or that you run the boiler a little less.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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