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  1. #1

    Difference in Carrier Air Handlers?

    Can anyone tell me what the difference is between the Carrier FB4CNP024 Air Handler and the Carrier FX4DNF025 Air Handler? A contractor quoted me a Carrier 25HCD424 2 ton 14 SEER heat pump with the FB4CNP024 air handler and a Carrier 25HBC524 2 ton 15 SEER heat pump with the FX4DNF025 air handler. Another contractor quoted me the FX4 air handler with both heat pumps. The Carrier site doesn't really explain what the difference is between the FB4 and the FX4 air handlers. Is one better than the other? Are they interchangable to each heat pump? Thanks very much.

  2. #2
    Join Date
    Oct 2014
    Location
    SW-Florida
    Posts
    3
    Quote Originally Posted by WCentralFlorida View Post
    Can anyone tell me what the difference is between the Carrier FB4CNP024 Air Handler and the Carrier FX4DNF025 Air Handler? A contractor quoted me a Carrier 25HCD424 2 ton 14 SEER heat pump with the FB4CNP024 air handler and a Carrier 25HBC524 2 ton 15 SEER heat pump with the FX4DNF025 air handler. Another contractor quoted me the FX4 air handler with both heat pumps. The Carrier site doesn't really explain what the difference is between the FB4 and the FX4 air handlers. Is one better than the other? Are they interchangable to each heat pump? Thanks very much.
    I believe the Primary (maybe only) difference is:
    FB model has "piston" refrigerant control device.
    FX model has "TXV" refrigerant control device.
    As far as I know, they both use the same fan motor and coil.
    If they are ARHI rated and manufacturer rated with the same outdoor unit, they should be interchangeable. Coil and refrigerant control (and charge) can be a bit critical on heat pumps, so the MUST be matched correctly.

    I would say that neither is "better" than the other, it depends. TXV refrigerant control tends to be more tolerant of widely varying temperature conditions, which "may" result in real world operating system efficiency. On the other hand, the piston control has been used for decades, and "may" be more reliable.

    A clue may be that higher efficiency systems "require" a TXV to get the higher SEER rating.

  3. #3
    Thanks so much for your reply, FL-Ruben. I suspected it had something to do with the TXV but wasn't sure. The TXV is in our old Carrier air handler being replaced, not sure why the contractor didn't quote "apples for apples". Thanks again for your help.

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