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EDR Calculation

STvex Member Posts: 71
Does anyone know the EDR of this in the wall radiator. Its 32 inches across and 15.5 inches in height if measured from top of grate to top of radiator or 20 inches if measured from leg to top of radiator. It has about 14 sections. Its about 3 to 4 inches in depth. Help is appreciated.


  • BobC
    BobC Member Posts: 5,431
    That should have an EDR of 31.5 according to the Governdale spec sheet.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • STvex
    STvex Member Posts: 71
    Thanks. i was thinking the EDR was close to 60 for that radiator. I have a 1600 square foot house and a 32 year old Weil EG-45 boiler at 150,000 btu. I think this boiler is a little oversized. With the 31.5 EDR for two of the recessed radiators, I am coming with total BTU needed of less than 100,000, how can I be so off? Currently, my boiler worked fine. I have 9 radiators, 7 tube style and 2 recessed like the picture above.

    Radiator 1: 18 inch height, 6 columns, 18 sections- EDR=18*3=54
    Radiator 2: 22 height, 20 sections, 3 column- EDR=20*3= 60
    Rad #3: 22 height, 18 sections, 3 colums- EDR=18*3.5=63
    Rad #4: 22 height, 8 sections, 3 colums- EDR=8*3= 24
    Rad #5: 24 height, 16 sections, 5 columns- EDR= 16*3=48
    Rad#6: 22 height, 6 sections, 4 columns- EDR=6*3=18
    Rad # 7: 24 Height, 12 Sections, 5 Columns- EDR= 12*3.5= 42
    Rad 8 and 9, pictured above, 32 EDR Each

    Total EDR= 373

    373*240 (steam) =90,000 btu

    I am I missing some thing, why is 90,000 so off from the 150,000 i have?

  • KC_Jones
    KC_Jones Member Posts: 5,537
    90000*1.33 (pickup factor)= 119700
    119700/.82 (approximate boiler efficiency) = 145975
    That boiler is rated for 392 sq ft of EDR so you are actually pretty good. About 5% over sized by the ratings. I will add that it has been discussed more often lately about sizing steam closer to the heat loss with less pickup factor, but what I just stated above is the way it has been done and proven for years.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • 4Johnpipe
    4Johnpipe Member Posts: 479
    Is it "Sunrad"?
    Considerate People, Considerate Service, Consider It Done!
    email: [email protected]
  • STvex
    STvex Member Posts: 71
    Thanks guys looks like I had the right boiler
  • Jason_13
    Jason_13 Member Posts: 304
    You size the connected load and choose from the boiler manufcaturer's Sq Ft steam rating on the brochure.
    The sunrad when recessed losses 10% output which can be deducted from EDR.
    Do not add anything to the EDR number