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New installed steam boiler may be too large

Sparkley Member Posts: 1
Hello all,
I am a home owner that would very much appreciate your help. We have just had our steam boiler replaced. I created a chart of all of the radiators in our home that gave the height, number of columns and sections as well as depth of the radiators to the contractor (who is a well respected expert in the area). While I should have finished sorting out how to calculate the rest of the equation, I did not and our 200 BTU boiler was replaced by a 207 BTU boiler.

I was organizing all of the material for the new unit today and for "fun" thought I would see if I could figure out how to do the rest of the calculations on the chart. Best I can tell, the EDR is between 372- 425, for a 2,200 square foot house.
I utilized 240 BTU per square foot to determine the BTU required.

I took into consideration 16% sea level adjustment and 20 percent efficiency adjustment but even with this I think the boiler has about 62,000 BTU more capacity than needed. I have not taken into account any of the piping of the system just the radiators.
Am I doing something wrong in my calculations?

I'm new to this forum but just read a post that talked about not over sizing the boiler or you get short cycles. Maybe my calcs are way off but if they are right is there anything I should do with the system since the boiler is already installed? All tips would be very welcome.
Thank you Maggie.


  • Jamie Hall
    Jamie Hall Member Posts: 23,428
    It's even easier than you are making it out to be. Take the EDR figure you calculated -- 327 to 425 -- and compare it to the nameplate rating on the boiler. It's there...

    Don't worry about changing to BTU and worrying about efficiency and all that. The boiler people have done that for you.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KC_Jones
    KC_Jones Member Posts: 5,741
    Also if you would like to determine the exact EDR of the rads post your information and pictures of the rads and I'd be happy to crunch some numbers for you.

    Unless you have some unusual radiation it's pretty straight forward.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    EBEBRATT-Ed Member Posts: 15,613
    The boiler rating also includes a piping and pick up factor of 1.33 built into the boiler rating which may be skewing your btu #s of the boiler.

    The correct btus is sq feet of installed radiation x 240 btus/ square foot x 1.33 piping and pick up factor.

    But the easiest way is to just total the EDR of all radiation and compare that to the boiler EDR or square feet of steam # on the boiler name plate.
    The manufacturer has already added the 1.33 pick up factor into it's sq ft rating