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  1. #1
    Is there a 'rule' on how long the A/C should cycle off before coming on again. I have heard it damages the compressor but don't know why. Is 5 minutes okay?. Also, do all thermostats have built in coding to prevent short cycling? Thanks

  2. #2
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    no, not all stats prevent short cycling. Yes five minutes off then back on again seems short, how long does it run before shutting off?

  3. #3
    Join Date
    Apr 2003
    Location
    California
    Posts
    631
    most digital stats will give you a delay of 5 or so, also some condensors have a built in timer,sometimes... most heat pump units have a delay also....the delay is a good thing, especially on a recip, most manufactures say a scroll will equalize right when it shuts down but I still believe in the delay,,give that baby a break...also remember analog type stats have no delays but the majority of digitals do...

  4. #4
    Join Date
    May 2005
    Posts
    428
    depends on how well your house is insulated

  5. #5
    Join Date
    Apr 2003
    Location
    California
    Posts
    631
    thjer is also many stats that have a programing option to remove delays, keep the delay on whenever possible...

  6. #6
    The a/c will run for about 10/15 minutes before shutting off. Yes, its oversized. Then as the cold air sinks to the lower house levels (no a/c ducts) and the warm air rises the temp goes back up the 1 degree for the thermostat to close again. This takes 5-10 minutes. Is that sufficient?. Can I get a more expensive thermostat to adjust off time or maybe have it 'wait' until the room temp jump's 2 deg F.


  7. #7
    Join Date
    Feb 2004
    Location
    Tucson AZ
    Posts
    55

    Cheaper Solution

    You can replace the Thermostat with a switch! That way you can cycle your oversized system that has an improper duct system when ever you want. P.S. Remember it takes @ 9 min. for your unit too reach the rated efficiency. Don't let it short cycle.

  8. #8
    Join Date
    Apr 2005
    Location
    Tampa, Florida
    Posts
    1,634
    Running for 10-15 mins on isn't necessarily bad, as this works out to approx 3 cycles per hour, well within normal limits. Now, if this was the hottest day of the year and it's doing this mid-day, your system's waaay oversized and you'll probably need to adjust the stat's differential/anticipator for longer run times. If it's only off for 5 mins every time, then you're definitely short-cycling it... 10 mins or longer is good. Longer run times = longer equipment life due to less starting & stopping, but at the expense of comfort (wider temperature swings) while shorter cycles lead to more equipment wear, lower efficiency, and less temperature swing.

  9. #9
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    most compressors are rated for FOUR starts per hour.

  10. #10
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    3,948
    My Carrier stat has a 15 minute timer between starts as well as a 5 minute break between cycles.

  11. #11
    Thanks for all the advice. I found a stat on which I can adjust the temp increase before cycling and it seems to work well.

  12. #12
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,897
    If you're in a dry climate, you might want to consider running the blower full time to balance out temps and reduce short cycling.

    It will increase the bill though - significantly.

  13. #13
    Join Date
    May 2002
    Location
    Colorado
    Posts
    697
    I think Ps2's question concerns protecting the compressor from damage. Yes, Ps2, 5 minutes is long enough.

    Not all thermostats have a built-in delay. And not all condensing units have one either.

    One of the advantages of better units (more expensive) is that they have restart delays and other features to prevent damage if something goes wrong. Home builders aren't about to pay for such things -- but they do get a lot of decibles for their money.

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