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  1. #1
    Join Date
    Nov 2004
    Location
    Clarence, NY
    Posts
    34
    Hi Gang,

    I'm trying to complete some energy calcs to convince myself to go hydronic plus separate AC vs. FHA and AC. But one "deal killer" occured to me.

    Assuming an 84% AFUE gas boiler, what will the REAL AFUE be during June-September when I am only needing abuit 2.5M BTU input to make DHW? This is for a 50MBH IBR gas boiler. Any ideas? Seems that the summertime AFUE is going to be kinda low comparted to a chinzy standard tank.

    TIA,
    Mark
    Mark Adams
    Clarence, NY

  2. #2
    Join Date
    Jan 2002
    Location
    New Hampshire
    Posts
    1,285

    That's funny

    AFUE is ANNUAL Fuel Use Efficiency.

    Combustion efficiency is a whole 'nother animal.

    Noel

  3. #3
    Join Date
    Nov 2004
    Location
    Clarence, NY
    Posts
    34
    Noel,

    I understand the problem. Combustion efficiency goes down when cycles are shorter. This will effectively lower the AFUE. I know its apples and oranges, so let me rephrase as a statement , you fill in the blank.

    For DHW production only, a gas water heater with an EF=??? is the equivalent to a 50MBH IBR boiler that operates at 84% AFUE with a high quality indirect tank.

    Better?

    Thanks,
    Mark
    Mark Adams
    Clarence, NY

  4. #4
    Join Date
    Nov 2001
    Location
    Moose Jaw, Saskatchewan, Canada Occupation:Interprovincial Plumber, Commercial Gasfitter Interests:
    Posts
    2,412
    An ef of .4 is equal to about 40% afue.
    I love my job, but paydays Thursday

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