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  1. #1

    Frown A/C Less Efficient since yesterday.

    I have 2 units, one upstairs, 1 downstairs. The units are 8 years old. Either unit would usually have no problems getting down to 70 degrees even if it was 100 degrees outside, but I don't push them that hard Normally I keep the daytime setting for both at 75 and evening setting upstairs at 73 while downstairs is 77.

    The problem: Yesterday around 9:30pm I discovered it was warm upstairs, 77 when it should have been 73. The house is comfortable, but the downstairs unit is working extra for the upstairs unit. Cannot get the upstairs below 75, yet I can get downstairs below

    What I did: I tested the downstairs unit and it was able to get to 73 with no problem. I replaced both intake filters 3 weeks ago, they look good still. I checked the units outside, both fans are working, one seems to be blowing hotter air than the other, but no dead animals, weeds, or debris inside. I checked the airflow from the returns, it seemed cool, but not as cold as usual, and it seemed less cfm than usual. I then had an epiphany: I called an a/c company to come in today and check the system.

    What he did: He tried selling me a manual thermostat, saying the digital-programmable thermostat had gone bad, {bull!!}, and a condensor cleaning, and a service plan, all for the low, low price of $$$$!!

    My disgruntlement: I paid him for his service call, but not everything else he wanted, because, he did not bother to try swapping out the thermostats from downstairs to upstairs to verify his theory! I did the swap afterward and, just as I suspected, the same problem upstairs and the downstairs works just fine, therefore, NO thermostat problem!

    What I would like: Ideas as to: Why the airflow is less, Why the air feels less cool.
    Last edited by jpsmith1cm; 07-23-2012 at 10:17 PM. Reason: pricing

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,871
    ...What I did: I tested the downstairs unit and it was able to get to 73 with no problem. I replaced both intake filters 3 weeks ago, they look good still.
    I checked the units outside, both fans are working, one seems to be blowing hotter air than the other, but no dead animals, weeds, or debris inside.
    I checked the airflow from the returns(?), it seemed cool, but not as cold as usual, and it seemed less cfm than usual.
    I then had an epiphany: I called an a/c company to come in today and check the system.
    What he did: He tried selling me a manual thermostat, saying the digital-programmable thermostat had gone bad, {bull!!}, and a condenser cleaning, and a service plan, all for the low, low price of $$$$!!
    It doesn't sound like he did a thorough performance analysis of the upstairs system.(?)

    There is a reason that one condenser is blowing a lot hotter air than the other one. Which unit, upstairs or downstairs is blowing the hotter air?

    You need to get a humidity gauge for use indoors (upstairs & downstairs) & also take the indoor supply air & return air temps on both floor levels.

    You also need to check the temp-rise off both condensers & subtract the outdoor temp from that discharge air temperature.

    If the upstairs airflow has dropped a lot, then the blower & airflow system, ductwork, etc., needs to be thoroughly checked.

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