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  1. #1
    Join Date
    Jul 2012
    Location
    St. Augustine, Florida
    Posts
    2

    Analysis Paralysis on new HP and AHU

    I currently reside in Northeast FLorida in a 2070 SF Stucco 1 level home. Looking to replace an 11yr old Tempstar 3.5t HP and 4.0t AHU(Builder grade, 10 Seer). Current tech said condensor is starting to show signs (pulling high LRA?) of failure soon.
    I've had 4 contrators provide their quotes and the sizes are different. I'm not aware of any performing any load calculations as they all left to provide quotes. The current system for the most part has been doing the job but it seems to run a long time during the afternoon. 60min on and 10 min break before starting again for another 60 min.

    Quotes from 4 contractors received were all for 15+ seer.
    1. Lennon 3.5 ton inside and out (from current contractor and tons does not match original equipment they installed)
    2 Rheem 4 ton inside and out
    3. Trane 15XR 4 ton out and 5 ton Hyperion Tam7 variable speed ahu. - is 5ton overkill?
    4. Trane 15XR 3.5 ton out with 3.5 Hyperion Gam5 ahu.
    Carrier performance series 3.5 inside and out

    How can the tons be different from each contractor? Will a 4 ton be considered too much and have humidity issues and short cycles?
    I've read online that the coverage area should be 400sf per ton, 500sf per ton, and 500-600sf per ton. What is the standard in 2012?

    I'm really lost on making a good decision.

    A lot of places say trust your contractor but I've only used one and their guote for the lennox is almost $2000 higher than the rest for a comparable model so they are hard to trust and they always want me to replace this and that when they do there Bi-yearly checkup.

    Any direction toward what would be the best ton for house would be appreciated.

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,031
    There can be reasons why it's pulling high (LRA) Locked Rotor Amps, if it actually is...

    Has the compressor ever failed to start? Does it already have a start kit installed, or none?

    Those 10-SEER units were good performers...

    Before I'd do a complete replacement, I'd try to find someone that really knows how to thoroughly troubleshoot an entire system; there may be some problems that need addressing...there may or may not be specific compressor problems.

    All connections should be checked for voltage drops, the compressor terminals should be checked for signs of needing replacement, etc.

  3. #3
    Join Date
    Jul 2012
    Location
    St. Augustine, Florida
    Posts
    2
    This is the second compressor in the unit. The first compressor failed in the second year of service. I'm not sure about a start kit.

  4. #4
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,031
    Quote Originally Posted by bdellin View Post
    This is the second compressor in the unit. The first compressor failed in the second year of service. I'm not sure about a start kit.
    I am guessing there were problems with the original install; could be a problem with lack of proper piping for oil return to the compressor.

    There are a number of other miscues that can cause early compressor failure...everything concerning the entire system needs to be examined for problems that need fixing to help prevent future failures.

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by udarrell View Post
    I am guessing there were problems with the original install; could be a problem with lack of proper piping for oil return to the compressor.

    There are a number of other miscues that can cause early compressor failure...everything concerning the entire system needs to be examined for problems that need fixing to help prevent future failures.
    X2

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