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Proper sized heating unit?

I'm in the middle of an addition/renovation adding 1500 sq. ft. to my current 1500 (all single floor) in WNY. I will be removing my forced air unit and replacing with radiant heat throughout. Addition is 3/4 slab with a 288 sq ft. basement connected to my current full basement. My contractor has recommended a Peerless Purefire 4 (210,00 B.T.U.) unit. Seems a wee bit large to me... I haven't had a heat loss assessment made.


  • BobC
    BobC Member Posts: 5,260
    A detailed heatloss has to be done or it;s all guesswork.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Snowmelt
    Snowmelt Member Posts: 1,296
    even if you did 50 BTU per square foot you only need 14,400.
  • nydoodles
    nydoodles Member Posts: 3
    Went to and this estimated a 125,000 BTU requirement.
  • Rich_49
    Rich_49 Member Posts: 2,666
    Never let him in your house again ! Traveled to Plattsburgh in Nov. 14' where the homeowner had a 145,000 BTU boiler , why so big ? Snowmelt ! That boiler is much too large for the house , roughly the same size home as yours after completion .

    We had to add an 80 gallon buffer tank to calm the mod con down among other measures to actually melt snow and get ALL the upstairs rooms comfortable .

    get a room by room heat loss done by someone or perform it yourself , you'll be amazed .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • nydoodles
    nydoodles Member Posts: 3
    Rich and Snowmelt, Thanks for your comments. I'm scheduling a heat loss workup.
  • RobG
    RobG Member Posts: 1,850
    I don't know who will be doing your heat loss but I would recommend looking up Slantfin Heatloss Calculator and doing it yourself. You can post your results here and we can review and advise. 210,000 BTU's is INSANE for a 3000 Square foot home unless it has no insulation and is in the north pole!
  • Jamie Hall
    Jamie Hall Member Posts: 17,840
    Second, third, fourth... get that heat loss done. The place I care for is over 7,000 square feet, essentially uninsulated, and uses 300,000 BTU on a -10 F day. The boiler is rated at 385,000 BTU. Your 210,000 BTU has to be oversized.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England