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steam radiator replacement, supply pipe sizing

aircooled81 Member Posts: 205
where can I get a chart to tell me the edr or btu/hr for 1/2 through 1" supply piping, to individual steam radiators? basicaly 1 to 5 psig.
I am on a job, where I need to replace more than a dozen fin tube steam radiators with steamview steel radiators. the fin tube radiators are 4 row, single element, tubes look to be 1/2" or 5/8 diameter. I was not able to locate a sizing chart for steam fin tubes this small.
In some instances, I am removing a 2' fin tube element, and installinf a 6' steel radiator. The piping to and from the exsiting radiators are 1/2".
some of the 2nd floor radiators are 3/4" and 1" supply, but they all utilize 1/2" returns. these are the 3' and 4' fin tube radiator elements.

by the way, this is a 2 pipe, condensate pumped return system, not a vacuum system, which they run at 5 psi. all of the radiators are individually piped from the basement, where 4 supplys and or 4 returns horizontally branch off of the main lines, then tee off all before they climb the walls.

so, I calculated a 6' steel radiator (10,659 btuh) at 44.41 edr. I found on engineers tool box, 1/2" pipe at 5 psi will provide 48 edr @ 50 ft/sec. I think I am safe to reuse these 1/2" supplys, as I am just swinging the exising piping over a foot or two horizontally in the wall to catch my new rough-in penetrations.

any opinions in the matter?


  • gerry gill
    gerry gill Member Posts: 3,078
    something doesn't sound right with that system. I have mini tube and seldom hit 2 psi. Can you post some pictures? are there any original components that identify the system? I've never seen a standard steam system with pipe that small.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • aircooled81
    aircooled81 Member Posts: 205
    i beleive this building was built in the 1930's. It's a very old college dorm. under every window is a coil type radiator. somewhere down the line, trv's were installed, and condensate traps may have been added at that time too?
    the boiler is locate outside, above grade, which speaks to why there are transfer and condensate pumps in the basements.
    they take 10 to 15 psi steam at the boiler, and drop it to 5 psi at the building(s). this boiler feeds 3 buildings.
    I have not found one engineer yet who can speak to the original design, if the boiler was ever in the basement, or how much is still original. whether this was original one or two pipe, or if these were even the first radiators.
    if I find out more, you'll be the first to know. I am very interested myself, but asking someone about something installed 85 years ago just doesn't seem to get the same interest.
    maybe i'll make this my mission, do some research and likely the college would add it to the historic notes for these buildings?
  • Steamhead
    Steamhead Member Posts: 16,736
    Sounds like a Webster "Hy-Lo" system, where the boiler ran at higher pressure and there was a PRV for each building. Are any of the original traps still there? If so, can you see who made them?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • cmeyers011
    cmeyers011 Member Posts: 2
    how do i tell if a steam system can handle a radiator or 2. for instance adding them in the basement for a now finished area?
  • BobC
    BobC Member Posts: 5,473
    The first step is tp look at the boiler information plate and find out what the EDR rating is. The second step is to measure the EDR of all of you radiators and total them up.

    Subtract the radiator EDR from the boiler EDR, that will give you the available EDR that you can add to your system.

    The file attachment will tell you haw t determine the individual radiator EDR.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    JUGHNE Member Posts: 11,021
    I would suggest starting a new thread. For basement radiation you need to consider where the boiler water line is in relation to the new added rads and also if you have a wet return below the new rads.