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Steam pipe split into two branches!!!

Gocel Member Posts: 5
Hello, I have a one pipe steam heating system and I am trying to install a new steam radiator in a small kitchen. I would like to know, if it is ok to split the pipe that brings steam into the room that is next to the kitchen into two branches with independent shut off valves. The size of the pipe is 1 ¼” and I am also planning on using Danfoss Thermostatic valves to control the heat. The next question is; if making two branches out of one is ok then would it also be ok to reduce the size of the pipe branches from 1 ¼ “ to 1”? Thank you for your time.


  • Jamie Hall
    Jamie Hall Member Posts: 15,445
    You need to know the EDR of the radiators to determine whether the branch you are splitting can handle the extra load, and whether the branches can be sized smaller.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gocel
    Gocel Member Posts: 5
    Thank you for your reply Jamie. The radiator I currently have is half the size than the original massive radiator that was there 23 years ago. I currently have in that room a Burnham Slenderized 4 Tube, 19" High, 12 Section Radiator that still overheats the room. The new radiator I want to install is a Burnham Slenderized 4 Tube, 19" High, 8 Section. My house was renovated insulated an new windows were installed and that is the reason that I also want to use thermostatic valves. Would I still need to know the EDR. Thank you for your time.
  • Fred
    Fred Member Posts: 8,516
    A 4 tube radiator, 20" tall is 2.25 EDR per sectionso 8 sections will be a total of 18 EDR. Two of those will total 36 EDR. A 1.25 supply pipe will support about 55 EDR so you should be able to do it and feed each one with a 1" supply off of the 1.25 pipe. Don't bull nose the split when you Tee off of the 1.25" pipe. A 1" pipe will support about 25 EDR. It should work as long as pressures are low and both radiators properly/equally vented.
  • Gocel
    Gocel Member Posts: 5
    Fred, thank you very much for such a great technical information. I really appreciate the help. Thanks
  • Danny Scully
    Danny Scully Member Posts: 1,319
    edited November 2017
    We need to know a bit more. How long is the runout? How long will you be extending the runout?
  • acwagner
    acwagner Member Posts: 507
    Also, how much vertical space above the existing pipe do you have? It's recommended when you branch on a 1-pipe system that it come off the pipe at a 45 degree angle, and you'll need to maintain pitch to the new radiator so everything drains.
    Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
    18 Ounce per Square Inch Gauge
    Time Delay Relay in Series with Thermostat
    Operating Pressure 0.3-0.5 Ounce per Square Inch

  • Gocel
    Gocel Member Posts: 5
    The 1 1/4" steam pipe is at the end of the basement and from there I need two pipe runs. One is a 5' run and the other one is 4' run both horizontally and 1' for both vertically. Thanks again for all the help.
  • Fred
    Fred Member Posts: 8,516
    You should be fine. Just make sure you have good pitch on the horizontal.
  • Gocel
    Gocel Member Posts: 5
    Thank you Fred.
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