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IBR rating vs BTU

danw884danw884 Posts: 2Member
Hi All,
Happy 4th! I currently have an oil fired boiler that is 25 years and time for replacement . It has a Net IBR rating of 104000 but no BTU rating. All the boilers I have been looking at are just rated in BTU's. I want to do a like for like replacement. Just wanted to make sure I'm getting the right one.
Any advice will be appreciated.


  • Jamie HallJamie Hall Posts: 11,875Member
    The Net IBR rating is in BTUs -- it is the rated BTU output of the boiler under certain conditions.

    That said, choosing a new boiler based on simply replacing what's there with the same size doesn't always work. If it's a hot water system, the new boiler must be sized based on the actual heat loss of the building. Slant/Fin, for one, has a nice calculator to figure that out. If it's a steam boiler, then the EDR rating of the boiler -- which is the net BTU corrected for pickup load and expressed as square feet -- must be similar to the actual load of the heating system's radiation, also expressed as square feet. Any other approach may lead to a boiler with is significantly undersized for the job -- or, far more often, significantly oversized. Neither error is good; the former will give you unsatisfactory heat, and the latter will just cost you money.

    Don't assume that the previous boiler was right...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • danw884danw884 Posts: 2Member
    Thank you Jamie
  • SteamheadSteamhead Posts: 13,503Member
    @danw884 , where are you located?
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • rbeckrbeck Posts: 57Member
    Most hot water boilers are 70% - 90% oversized.
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