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  1. #1
    Join Date
    Feb 2008
    Location
    NY
    Posts
    99

    Are the tech’s recommendations about A/C night setback reasonable?

    I guy a work with in Atlanta called me and said a HVAC tech came to his house and said that he (the home owner) was setting back his stat too far. He said 80 at night was too great of a difference from 72 he sets the stat to in the morning. The Tech said only to set the night stat to 76 because the compressor was working too hard and too long to get the temp back down. He was also told if he does not set it back too much it will run in shorter "runs" and it will have time to “rest”
    Sounds like hack advise to me. I was under the impression that short cycling is bad and long steady runs are more sound for the equipment.

    I want to tell this co-worker that the guy is a hack and don’t let him comeback to his house but since he is many states away I thought I would get a pro opinion.

    Thanks…

    PS - guy lives near Duluth GA - if anyone has the name of a good company in that area I will pass it along...

  2. #2
    Join Date
    Apr 2001
    Posts
    669
    Quote Originally Posted by jrongo View Post
    I guy a work with in Atlanta called me and said a HVAC tech came to his house and said that he (the home owner) was setting back his stat too far. He said 80 at night was too great of a difference from 72 he sets the stat to in the morning. The Tech said only to set the night stat to 76 because the compressor was working too hard and too long to get the temp back down. He was also told if he does not set it back too much it will run in shorter "runs" and it will have time to “rest”
    Sounds like hack advise to me. I was under the impression that short cycling is bad and long steady runs are more sound for the equipment.
    I want to tell this co-worker that the guy is a hack and don’t let him comeback to his house but since he is many states away I thought I would get a pro opinion.
    Thanks…


    Tell your freind I said;

    and to lose that plumber's phone number.

    Jabs

  3. #3
    Join Date
    Jan 2008
    Posts
    95
    It is not going to hurt the unit to have those long run times, but if the unit is sized correctly than an 8 deg set back on a hot night may take a long time to recover.

    A properly sized a/c is designed to maitain tempature, not cool the house down from a set back.

    I have a lot of people call on a 95deg day and say, "I just got home and it is 85 degs in my house and the a/c has been on for 2 hours and hasn't cooled down at all". Well it is not supposed to.

    Central A/C is not like the a/c in your car.

  4. #4
    Join Date
    Jan 2008
    Posts
    95
    It is not going to hurt the unit to have those long run times, but if the unit is sized correctly than an 8 deg set back on a hot night may take a long time to recover.

    A properly sized a/c is designed to maitain tempature, not cool the house down from a set back.

    I have a lot of people call on a 95deg day and say, "I just got home and it is 85 degs in my house and the a/c has been on for 2 hours and hasn't cooled down at all". Well it is not supposed to.

    Central A/C is not like the a/c in your car.

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    I won't say he's a hack. he is mistaken though. You may find that many pro's on this board have the same opinion that setting it back that far is not good, and won't save any money.(I know it will.) I set my own back that far during the day.

    The compressor and fans are continuous load motors and running 24/7 won't harm them.
    Next time you set your own A/C back 8 or 10*, when it comes out of set back, and catchs up and shuts off. Pay attension to it, it will short cycle back on usually atleast one time due to the furniture and walls still having more heat in them then was in the air.
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  6. #6
    Join Date
    Aug 2007
    Posts
    45

    DOE Recommendations

    DOE recommends a setback around 5* for summary A/C and about 10* for winter gas heat, and estimates this will save about 30% on utility bills.

    According to their studies, setting back much more than this will not save much more...

    But individual systems and houses are all different, and thermal mass plays a big roll in performance and savings..

  7. #7
    Join Date
    May 2005
    Location
    Kathleen, Georgia
    Posts
    68
    I usually recommend 4-5 degrees depending on the customer

  8. #8
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    80 summer, 60 winter when on vacation --
    else, depends upone one's lifestyle & what they will tollerate. --

    if one has a programmable t-stat, come back from the 'set-back' in 2-3 steps -- like I did in 1987 -- took 3h, but day care was set-back from 6p to 6am -- Lewisburg TN.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  9. #9
    Join Date
    Mar 2003
    Location
    PA/DE area
    Posts
    1,535
    See that photo of the GTO,it has 3.5 tons of a/c in it( A6 compressor)it almost died when I read that.
    It's NOT the BRAND,it's the company that installs it!!!!!

  10. #10
    Join Date
    Dec 2004
    Posts
    201
    Would you still recommend a set back on a 2 speed system?

  11. #11
    Join Date
    Jun 2007
    Location
    south carolina
    Posts
    176
    Ive seen it go both ways some houses it's efficient others its not so try it both ways and see for your self.

  12. #12
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Quote Originally Posted by filterchanger View Post
    Would you still recommend a set back on a 2 speed system?
    Yes. It will just go to second stage if it needs to.
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  13. #13
    Join Date
    Mar 2008
    Location
    Central Maryland
    Posts
    246
    Quote Originally Posted by jrongo View Post
    He said 80 at night was too great of a difference from 72 he sets the stat to in the morning. The Tech said only to set the night stat to 76 because the compressor was working too hard and too long to get the temp back down.
    ...
    PS - guy lives near Duluth GA
    Is this a retiree who stays home all day and sleeps in the basement at night? I just don't get the reasoning why the homeowner sets his stat like that.

    In the heat of the Summer, I set my A/C to 72 at night, when it is cheapest to cool and I enjoy sleeping without sweating, and 78 during the day while I'm gone. If I thought that it would dehumidify sufficiently to set it at 80 during the day, I would consider it.

    Catching up in the late afternoon does take time, but with all that cool air blowing around, and the house starting out dehumidified, it's not that bad coming home.

    -HF

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