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Thread: AC run time

  1. #1
    Join Date
    Feb 2005
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    I had a new 3 ton carrier infinity system installed in March. My old unit was a 3 1/2 ton. So I questioned going smaller or maybe going to a 4 ton.
    My house is a 1900 square foot ranch style one story built in 1979.
    We keep the temp at 70 degrees because I like being cool.
    My hvac guy did all the load calc. and said new unit should be suffienct to cool the house. Two speed outdoor unit only comes in 1 ton steps.
    I live in the panhandle of Fla., so it is hot and humid.
    My question is the ac goes to high at about 9:30 in the morning and never cuts off again until 9:30 or so at night.
    It runs continuely all day. A couple of days this year, I've noticed 72 degrees in the heat of the day was all it was good for.
    Does the unit seem a tad small or is it normal and ok to run all day into the night with out a break
    I have noticed just comparing last years elec. bill to this years the cost is down a few bucks, even with a slight rate increase and new hot tub added.
    Thanks for any imput you might have.

  2. #2
    Join Date
    Nov 2000
    Eastern PA
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    Your electric bills are down when energy costs are up and we are having a hotter then usual year...I'd say your contractor did a great job.

    The most efficient HVAC system is one that runs constantly while maintaining the desired temperature.

    If possible, do a little more shading during those extreme points of the day to maintain that 70º. Actually, you should find that your home is more comfy at a higher temperature then your old system was because of the decrease in humidity.

    Overall, sounds like your contractor did real good., and ye shall find;..
    So always seek the Truth, not just what you want to believe to be true…
    Ecclesiastes 10:2 NIV

  3. #3
    Join Date
    Jun 2005
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    heat load calc. is usualy right on. if in dought at the top of this web site you can get the load calc. form and do it your self. its verry easy if you have a tape mesure and a little time. i have found that most homes from the 70s or older the furnace/air conditioner is over sized by as much as 25% so its not surprising to see you go down a 1/2 ton. lot of guys went by the more is beter rule. its not allways the case.

  4. #4
    Join Date
    Apr 2004
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    The real question would be was 70 degrees communicated prior to equipment selection? Even then I wouldnt size it for 70. You remove the humidity from the air and cool it to 70 and, thats downright cold. 72 on a 98 degree day with humidity, pretty damn good.

    Heres hoping you dont freeze the coil.

  5. #5
    Senior Tech Guest
    Yah...what Robo said...

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