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  1. #1
    Join Date
    Jan 2008
    Posts
    20

    Can a ARI paired air handler be too big?

    I've narrowed down my new heat pump system to two choices now. Both guys know their stuff, did thorough calculations, and have proven good quality work. Either one would do a great installation.
    the only difference between these two proposals is the air handler (and 1/2 ton delta in hp size). Both are paired in the ARI tables.
    awesome dude #1: Carrier Performance 25HPA536H HP paired with a Infinity FE4ANB006 air handler. 36000BTU, SEER=16.0, HSPF=9.3
    awesome dude #2:Carrier Performance 25HPA542H HP paired with a Infinity FE4ANF003 air handler. 40500BTU, SEER=14.5, HSPF=8.1

    #1 likes the large air handler because of the awesome efficiency ratings, and says that with the Infinity controller, the air handler won't deliver more air than necessary.
    #2 likes the smaller air handler because it falls in the perfect range to deliver an ideal 100cfm per vent. Our house has 10 vents and one return. He also worries that a larger air handler will have too much condensation on the larger coils which will dump moisture into our house.

    Can anyone provide any additional input on the large vs small air handler? Seeking an education...

  2. #2
    Join Date
    Jul 2005
    Posts
    5,576
    Carrier lists the HSPF of #1 as 8.4

    By using the same A/H as #1 instead of the one you listed, #2 would get 16 SEER with an HSPF of 8.7, a bit better than #1

    The question is, what size is actually needed? That would help you narrow it down a bit more.

    An oversized air conditioner will not dehumidify as well, but with these systems that isn't going to be a big issue because they have dehumidification capabilities. What will happen though, is that if you do not set the system for economy (no extra dehumidification), then you will not get the rated SEER. The amount that SEER will drop will depend upon the size of the condenser. If the condenser is oversized you'll get more of a drop in SEER than when it's sized correctly. If you only need 3 tons, then #1 will be an excellent choice, #2 not so much, even if you use the other AH. If you need 3 1/2 tons, then #1 is out of the question. The comment that you quoted about the coil size is misguided. The larger evaporator coil will improve efficiency, which is why these two air handlers provide differences in SEER with the same condenser. I won't go into the comment you made about dehumidification except to say that dehumidification and coil size involves a discussion that even some techs can't keep up with. FWIW, your contractor's comment is incorrect, but I suspect you misquoted him.
    Last edited by hvacrmedic; 03-04-2008 at 01:00 AM.

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,803
    The larger coil won't condensate more then the smaller one at same CFM.
    The ID unit should be matched to the SHR your house needs, not your contractors personal preference.
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