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New to Steam.

TLD Member Posts: 3
I have two steam boilers jobs that are both at 7,000 ft. elevation that I need help on. The homeowner in both cases wants a newer more efficient boiler.  On the first job there are four radiators; I was not given enough info to size them correctly so I did a little guesstimating with the help of the Burnham heating helper.  The radiators are the following sizes:

Qty,1=21" high-6" wide-17 section-est. length 30"

Qty,1=same dimensions-16 section

Qty,2=same dimensions-12 section

I came up with roughly 133 sq ft of steam that the radiators can produce.I was told it was a one pipe system with a 3 inch header and roughly 60 feet of 2 inch main, so it seems the pipe uses more sq. ft of steam than the radiators. Is this typical of a one pipe steam system or am I missing something?

P.S. The existing boiler is an Ideal boiler with a 7" flue and no rating plate.

The second job I have consist of eleven radiators with a capacity of 480 sq, ft of steam.  The existing boiler is an American Standard G-406,3b-j2,938 sq ft cap,9" flue, 375,000 in and 300,000 out.  The main is also about 60 feet of 2 inch. The house is an old Sears home that is 3 stories with the boiler in the basement.  I looked and found a smaller Burnham capable of handling the load,but do I just add 20 percent to the input for elevation and jump a boiler size or is there a better way make sure I am putting in the right boiler?  I also wanted to make sure I don't flood the smaller boiler with condensate. Any thoughts?


  • Jamie Hall
    Jamie Hall Member Posts: 22,897
    It's not that unusual

    for the gross area of the mains to approach the heating area of the radiators -- particularly in smaller installations.  That is one of the reasons to insulate them!  Generally we suggest 1" fibreglass...

    I'd have to double check, but it seems to me that the EDR of your 4 radiators may be a little low -- maybe not... I get a 21" 16 section 5 tube at 43, so I guess it's OK...

    If the mains are well insulated, you should be able to get away with the usual 1.2 to 1.5 pickup factor in both cases.

    You will also want to still run the lower pressures (2 psig maximum!  1.5 better) in spite of your altitude.  Don't be tempted to 'crank it up' to compensate.  The BTU output of the radiators will be slightly less than at sea level, though.  However, I would be inclined to ignore that in sizing the boilers; go with the EDR ratings in the usual way, I think.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Unknown
    edited November 2009
    High Altitude Steam

    I don't think that altitude affects the steam output as a steam heating works on latent heat. Think of it this way, if altitude affected the steam end then vacuum steam systems wouldn't be consider the "Cadillacs" of the industry! However altitude may affect the boiler end  and so I'd check with the manufacturers as to whether their boiler's output were affected by altitude.As Jamie mentioned insulation makes a HUGE difference and while more is better, 1 inch gives you the biggest "bang for the buck".

    Are these replacement units oil or gas?

    Also if you don't already have it, you might want to get Dan's book- "The Lost Art of Steam Heating"


    as it has a lot of info and discussion about the piping of the modern boiler and anything else you wanted to know about steam heating.

    - Rod
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    edited November 2009
    Boiling point vs. altitude

     Boiling point is a function of atmospheric pressure so it will affect heat output of a given size radiator. Even though the latent heat may not change, the boiling and condensing temperature is lower at high altitude. At 7000 feet water boils and condenses at 199 F, so this is the maximum temperature the radiator can reach, rather than 212 For more at sea level. Not a big difference, but worth considering.

    It is precisely for this reason that  vacuum systems were considered the best. The radiators could be made to condense water vapor at much lower temperatures than 212, thereby providing a more gentle heat during mild weather. Yet, when necessary during cold weather they could build pressure and provide full output.
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