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  1. #1

    Trying to understand

    Hi there folks, great forum. I am in Florida, Jacksonville

    I have a 1 ton unit cooling an area of about 480 Sq feet, adequate as I am told. On days under 90, no problem, but if the temp goes over 90, the temp starts to drift. For example, it is 93 today and my thermostat now reads 78. I have it set for 75. About 830pm tonight the temp will come down to 75.

    I've had the vents in the attic checked for leaks, nothing. I have a Fluke 116 and measure 97 at the low pressure line and 65 at the high pressure. This is inside at the blower end, outside measurements are slight lower. On a normal day my high pressure line is about 58 degrees. What could cause this drift in temp?

    Also, suddenl I have water dripping from my filter to the drip pan. I 've had the coils cleaned so thats not it.

    thanks
    Ron

  2. #2
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    Think you have answered you own question, Ron. Temps over 90 exceed your cooling capacity with regard to your current system. Make sure you keep the filters clean and have the unit serviced regularly but at 12,000 btus with 480 sq ft in Jacksonville, you have found you max cooling capacity.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  3. #3
    thanks for your reply. In your opinion, is the 1ton unit big enough for this space. I have 10 foot ceiling in the space as well.

  4. #4
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,887
    Quote Originally Posted by Ron_in_fla View Post
    Hi there folks, great forum. I am in Florida, Jacksonville

    I have a 1 ton unit cooling an area of about 480 Sq feet, adequate as I am told. On days under 90, no problem, but if the temp goes over 90, the temp starts to drift. For example, it is 93 today and my thermostat now reads 78. I have it set for 75. About 830pm tonight the temp will come down to 75.

    I've had the vents in the attic checked for leaks, nothing. I have a Fluke 116 and measure 97 at the (High small) pressure line, and 65 at the (Low) pressure (large line). This is inside at the blower end, outside measurements are slight lower. On a normal day my (Low) pressure line is about 58 degrees. What could cause this drift in temp?
    What was the outdoor temp & discharge air temp from the compressor when the small line was 97-F?

    What were the indoor supply-air & return-air temps, & the indoor humidity?

    Also, suddenl I have water dripping from my filter to the drip pan. I've had the coils cleaned so thats not it. thanks Ron
    We don't have enough information to tell you much of anything.

    There are a host of things that can reduce the capacity of an A/C system, including the duct system airflow being only one of them.

    Jacksonville FL summer design 94-f dry bulb, 77-f wet bulb 47% relative humidity.

    Check the air-infiltration-rate of your home & seal all the leaking areas possible, a 47% humidity at 94-f is carrying a lot of grains of moisture when it mixes with the cooler indoor air.

    A high infiltrating latent moisture heatload can greatly reduce the sensible capacity ratio of the A/C system.

    A good tech can do all the procedures that would optimize the A/C's performance, & help you address & reduce the heat-gain area factors of your home so the one-ton unit might keep you comfortable. -Darrell

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