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  1. #1

    Forced central air unit doesn't cool much

    I have a forced air central air unit. It takes exponentially longer to cool my living room down (the room where the thermostat is) compared to what I think it should take. The temp in my house if the system is off is around 80. I set the thermostat to 77 and it takes hours and hours to cool down to that temp.

    The air coming out seems pretty cold although I'm not sure how cold it should be. If the air temp is fine, perhaps the thermostat could be in a better location, it is beside a bookshelf; top right corner of the bookshelf hits the bottom left corner of the thermostat and it's about 3' from the corner of a room. Could there be any other possibilities?

    Thanks in advance.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,168
    Location of thermostat won't change how long it takes to cool the room.
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  3. #3
    If the thermostat is blocked to some degree then couldn't it be in a "dead zone" from the circulating air? In such a case, the room would cool down, but it would take the thermostat longer (or possibly forever) to sense that. No?

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,168
    You said it takes too long for the room to cool down.

    So is it taking long for the room to cool down?

    Or is the room cooling to a temperature lower then what you have the thermostat set for.
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  5. #5
    Sorry for the delay. I wanted to get some temps for you. As I type, my C/A is on with the thermostat set to 79. It's been on for about an hour and it's stayed at 79. I have a thermometer sitting in the middle of the room that reads 76.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,168
    If its over cooling, then changing location so it can sense true room temp will help.

    See how warm the thermometer in the center of the room says it is before the unit starts again.
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  7. #7
    Join Date
    Mar 2008
    Location
    South Mississippi on the Golden Gulf Coast. 100 degree heat and 90% pluss humidty.
    Posts
    46
    where is thermostat in relation to return air filter grill

  8. #8
    Join Date
    Oct 2007
    Location
    BC
    Posts
    354
    Set your thermostat at 77 and leave it there. Don't turn it off when it reaches 77 then wait until it's 80 to turn it back on. It will work much better that way.

  9. #9
    I purchased the thermostat last year and I think it's a pretty good one, based on the research I did last summer. It's a LUX TX500b.

    Here is the setup of the living room:

    At the top is the bookshelf next to the thermostat. On the right is the TV area with the out vent below. Opposite is the couch with an intake vent behind it. When I put a thermometer on the TV stand it reads 76.4. When I put it in the middle of the room where the air is aiming it's currently at 75.6 and still going down. The TV area - which I imagine is hot when on - is basically between the out vent and the thermostat which is additionally cut off from air in the middle of the room by the bookshelf (if such a cold air area exists). When I put a themometer on the bookshelf next to the thermostat it's reading 77.6 and still may be climbing (the thermostat currently reads 78). Is it possible for air by the thermostat to be stagnant in that corner where it's basically impossible to change? The difference between last summer when the temp situation was normal and now is the addition of the bookshelf...

    I've programmed the thermostat to turn on and go off at certain temps. When it's on, though, it stays at that temp basically indefinitely while the room does cool. I don't want it running forever (especially while I'm not there) for no reason.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,168
    Bad location for it.
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  11. #11
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,997
    I take it the T-stat is on an interior wall, but is it well sealed where the wires go through the wall, or a source of heat there?

    Do you have any fans to use for air circulation?

    Maybe the fpm velocity from the diffusers is too low to mix the room air.
    Check the furnace blower wheel blades for lint clogging, if so, the evap-coil may also need cleaning.

    The air will be colder with low airflow, you need to know it's the correct velocity to each room. - Darrell

  12. #12
    Quote Originally Posted by udarrell View Post
    I take it the T-stat is on an interior wall, but is it well sealed where the wires go through the wall, or a source of heat there?
    Correct. When I installed it, I stuffed putty into the hole where the wires go so there wouldn't be an issue of heat or cold coming up from the walls affecting the temperature guage.

    Quote Originally Posted by udarrell View Post
    Do you have any fans to use for air circulation?
    I don't although since it's been so hot, my gf has been begging for one in the living room...

    Quote Originally Posted by udarrell View Post
    Maybe the fpm velocity from the diffusers is too low to mix the room air.
    Check the furnace blower wheel blades for lint clogging, if so, the evap-coil may also need cleaning.

    The air will be colder with low airflow, you need to know it's the correct velocity to each room. - Darrell
    Last summer when I moved in, I had an issue with the AC where it would be on, but from the vents only came the slightest amount of cold air. When I had it checked out, we discovered that there was no slot in my system for the air filter to go so it was just sitting loosely inside the unit. This allowed dust, etc. to accumulate on some coils in the AC portion of the unit, disallowing it to function properly. The HVAC blasted the filth off and the system worked fine after that. This summer, I checked those coils and they weren't dirty at all. Could there be dirt in other areas?

  13. #13
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,997
    Last summer when I moved in, I had an issue with the AC where it would be on, but from the vents only came the slightest amount of cold air. When I had it checked out, we discovered that there was no slot in my system for the air filter to go so it was just sitting loosely inside the unit. This allowed dust, etc. to accumulate on some coils in the AC portion of the unit, disallowing it to function properly. The HVAC blasted the filth off and the system worked fine after that. This summer, I checked those coils and they weren't dirty at all. Could there be dirt in other areas?
    Did he clean the blower wheel blades? Don't knock any of the balance weights off the blades.

    FIRST, Clear the blade near any weights & mark their position on the blade. I also used to wrap the motor with a plastic bag.

    Yes, the coil could be blocked & dirty where you cannot see it.
    A bright light should be shined through the coil, the fins need to be squeaky clean.

    There's more but am quitting for now
    . - Darrell

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