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  1. #14
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,888
    Originally posted by mel221
    Thanks everyone.

    Here is what I know now.
    Attic Temp 109
    Return Air at grill - 79
    Return Air at handler - 81
    Supply Air at handler - 66
    Supply Air at register - 67

    This morning, I had these results
    Attic Temp 90
    Return Air at grill - 79
    Return Air at handler - 80
    Supply Air at handler - 60
    Supply Air at register - 60

    I am confident the supply and return ducts are sealed and not leaking.

    I think my problem is the 15 degrees of cooling I recieve in the afternoon. I measured the airtemp in the handler return by attaching the thermometer to the filter inside the handler. The handler itself is not leaking air.

    So, in the afternoon, when the air handler box is 109 degrees, the air handler cannot produce 20 degrees of cooling.

    udarrell, I will be looking over your materials. Thanks.
    First, the airflow may be too high for that small A/C system and during the day when it is hot the condenser is not doing an effective job, --coupled with an improper charge it will not cool efectively.

    In the morning you have a 20 degree split, during the day you only have a 14 degree split. The condenser can not handle the hot daytime hours. (Too little or too much charge.)

    The tech may have charged this system when the home was very hot and over charged it; or if it was cool it could be under charged.

    What is the super-heat (piston fed) and sub-cooling (TXV fed)? Get both figures irrespective of metering device.

    http://www.udarrell.com/ac-trouble-s...ubcooling.html

    This linked page will explain what too much airflow and overcharging a system will do!

    http://www.udarrell.com/aircondition...e-airflow.html

    Get an accurate charge in the system during a hot day!

  2. #15
    Join Date
    Sep 2004
    Posts
    654
    It appears the upstairs unit is undersized, but that is totally a WAG. What flagged me was the downstairs unit being 4 ton and the upstairs unit only 1.5 ton. How much sq. ft is the upstairs trying to cool?


  3. #16
    Join Date
    Jul 2005
    Posts
    3

    >> The tech may have charged this system when the home was very hot and over charged it; or if it was cool it could be under charged.

    This is the working theory. He is coming out tomorrow when its hot to review the setup. He originally charged the system in the morning.

    casturbo... I am fearful that the system may be undersized. While the upstairs floor area is about 500 ft2, the ceiling area includes an atrium for an additional 200 ft2. The upstairs return pulls warm air from the ceiling atrium.

    To make matters worse, the entire upstairs ceiling has afternoon sun exposure on the attic above. This upstairs structure provides shade for the rest of the downstairs area.

    And to make matters worse still, the supply air has an easy path to fall down the stairs.

    But, before I can conclude the unit is undersized, I feel I need to address the lack of 20 degree split in the heat of the afternoon. The 5 degrees of lost performance could easily be the capacity I need.

    Thanks


  4. #17
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,901
    quote:
    --------------------------------------------------------------------------------
    Originally posted by diegocentral
    I have faired pretty well at 400 sq ft. to a ton on my installs
    --------------------------------------------------------------------------------


    Wow. That's almost as good as checking a charge by listening to a TXV with a screwdriver & a suction line temp. of 58.


    ?????? is there a correction factor if the screwdriver is insulated? And what is it?
    No Heat No Cool You need Action Fast

  5. #18
    Originally posted by twilli3967
    quote:
    --------------------------------------------------------------------------------
    Originally posted by diegocentral
    I have faired pretty well at 400 sq ft. to a ton on my installs
    --------------------------------------------------------------------------------


    Wow. That's almost as good as checking a charge by listening to a TXV with a screwdriver & a suction line temp. of 58.


    ?????? is there a correction factor if the screwdriver is insulated? And what is it?
    gee whiz guys - what happened to 65/225 sweat to the knuckle ?

  6. #19
    Join Date
    May 2003
    Location
    chesterfield, michigan
    Posts
    93
    Sounds like the system is undersized.. just ran into the exact situation, based on the numbers you gave and where the air handler is brought back memories. We did a load calc based on a builder produced blueprint and he screwed up the actual square foot and windows and we came up 1/2 ton too small, because your duct is in an attic and based on total distance and temp in the attic your duct can gain upwards of 5-10 degrees so proper sizing is crucial.Call the installing company back to verify temps and pressures because your system very likely might be maxed out.

  7. #20
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    at this point size is not a factor since you stated no sweat pattern and no condensate comeing out
    but with the td it does seem strange
    it would be best to have the unit set up properly and see what happens then

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