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energy factor on an indirect?

GW Member Posts: 4,693
I have a customer who asked what the energy factor on an indirect, for tax reasons. The question threw me off a bit, is there an answer to this?

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Gary Wilson
Wilson Services, Inc
Northampton, MA


  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    Efficiency of indirects and tankless coils [seems] to be covered by "Combined Annual Efficiency" or "Combination Appliance Efficiency" standards of ANSI/ASHRAE 124-1991 Very frequently abbreviated as "CAE".

    If both the indirect and boiler are from the same mfgr you might be able to get ratings from them.

    Here's one definition I found:

    “Combined annual efficiency (CAE)” means [(SHF x Effyhs/100) + (WHF x Effyss/100) +
    (R x NHF x EF)] divided by [SHF + WHF + (R x NHF)] as defined in the applicable test method in
    Section 1604(e)(3).

    Do some searching and you should find just what those acronyms in the definition mean. (I've seen--and used--most of them on rare occasion, but for the life of me I can remember.)

    Found synopsis of a few papers, but couldn't access the papers themselves. One that used three different boilers (of increasing size) with the same system (including indirect) found:

    1) A fairly close correlation between AFUE and CAE.

    2) That the larger the boiler, the more both AFUE and CAE tended to be below the stated AFUE.

    Unless the tax code specifies some rating for CAE, the customer is probably out of luck for any tax deduction.

  • Dave Yates (GrandPAH)_8
    EF ratings

    Can be obtained from the mfgr of the indirect.
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