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  1. #1
    Join Date
    Jun 2008
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    Old air handler / new compressor. Won't cool?

    Ok, Im a totaly newb here and know enough about HVAC to be dangerous. Anyways, back in August of '05 my exterior compressor unit was replaced with a new Goodman 1.5 ton unit. The old one was an approximately 15 yr old Carrier. It was covered under a home warranty I had at the time. Anyways, ever since when the summer arrives (I live in AZ) my AC just does not work worth a darn. Once it gets about 100 out I have difficulty keeping my house below 80. The air handler inside is still an old Carrier. I have had the system serviced and the techs find no coolant leaks, the coolant levels are fine and the system is functioning. Even the transfer coils are clean and I am using a higher flow fiberglas air filter. Yet the AC will run non-stop from about 11am - 8 or 9pm just to keep the place at 80. My condo is 1040 sq foot and both my indoor and outdoor units are 1.5 ton. My thought is a new air handler with a similar SEER rating and a variable speed fan will rectify this problem. However several techs from several companies all give me different answers. So really what I need to know is if it is even worth replacing or not and if in fact it will help at all. Any advice would be greatly appreciated.

  2. #2
    Join Date
    Aug 2003
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    Sounds like your system is undersized... it probably was always a problem.

    Have a heat gain done on your home to find out if it was sizes right from the beginning.

  3. #3
    Join Date
    Jul 2000
    Northern Wisconsin
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    "The system is functioning" doesn't always mean that they did any checks to verify that it's functioning to it's full capacity.

    If the old 1.5 ton unit did the job without any problems, and all that has changed is the new outdoor unit then you're dealing with possibly a missmatch of equipment that won't produce, when the old unit went bad it caused a problem with the indoor unit components or when they installed the new outdoor unit they let something loose in the system that has plugged up a circuit in the indoor coil. There are other possibilities, but most aren't found by a 10 minute service call only looking at the outdoor unit.

    Give them a call back and see if they'll send someone out that can do a more complete evaluation of what's going on.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #4
    Join Date
    Jan 2004
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    Possible mismatch issue.
    Or, its possible the newer nominal rated 1.5 ton condenser doesn't have the same true BTU rating of the old unit.
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    How many times must one fix something before it is fixed?

  5. #5
    Join Date
    Jun 2007
    Round Rock
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    It sounds a bit undersized. Can't tell from the armchair. But probably the culprit. Maybe poor insulation, crappy windows, weatherstripping, etc...

  6. #6
    Join Date
    Jun 2005
    SW Wisconsin
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    If the old 1.5-ton handled the heatload okay, then the new condenser should probably do better than 80-F depending on actual load conditions.

    You didn't state the SEER level of the new condenser. The new higher SEER units have a smaller compressor. Many of them use a 16,500-Btu/hr compressor in the 1.5-ton rated condenser.

    There also could have been a problem with the quality of the install.
    The are numerous things that could be causing a reduction in nominal tonnage capacity.

    Hopefully, during peak load days it will be enabled to reach 76 or 77-F degrees.
    If it gets the humidity low, & you use fans to create air movement, you should be very comfortable. Here is a linked "Human Comfort Zone Chart."

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