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  1. #1
    Join Date
    Feb 2009
    Posts
    23

    Default whats the problem

    Hi,I recently had new central ac installed in my home. I live in New Jersey and the summer has been brutal to say the least. I usually keep the thermostat at 79 when the outside temp is 85-95. However when it is 95 degrees or higher outside,I put the set temp to 76-77 degrees. I've noticed that my home will not get any cooler than 79 degrees.Is there something wrong with the unit or could there be an insulation problem etc. I have a 2 story cape cod and the unit is a 2 1/2 ton Rheem. Any insight would be greatly appreciated.

    THANKS

  2. #2
    Join Date
    Jan 2009
    Location
    Needham, MA
    Posts
    559

    Default Re: whats the problem

    there's a few things it could be but my first guess would be the insulation in your walls, insualtion in the attic or above the ceiling upstairs and the windows not having low-E glass.

    anything you know about those issues? it's a good place to start.

  3. #3
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: whats the problem

    There is a calculation for figuring out how much tonnage you'll need. Some of it is straight forward math, some is estimating, such as how much shade that nearby tree will give. Sounds like the unit is undersized. Time to start speaking to your installer for a larger unit which they should upgrade for free since it was their mistake.

  4. #4
    Join Date
    Jun 2012
    Posts
    19

    Default Re: whats the problem

    What is the square footage? This may be a small unit considering the zone you are living in. Zone 3. Typically 1300 to 1600 sq feet for this area a 2.5 ton unit should work. But since the summer is unseasonably hot this may be all that it can muster.

  5. #5
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: whats the problem

    It's entirely possible that your unit in too small or your insulation is not perfect, but frankly, I think that you're demanding too much from your poor A/C.

    What I don't understand is why you want 79 when it's 85-95 outside, and then you want 76 when it's more than 95 outside.

    Since feeling comfortablly cool is a relative concept, put your thermostat at 82 when it's over 95 outside - and you'll see how well your A/C might perform. Also, make sure your filter is clean.

  6. #6
    Join Date
    May 2012
    Posts
    134

    Default Re: whats the problem

    Ridiculous...here in Central Florida, it's common to have 70-72 degree temp in 99 degree, humid weather.

    Call your installer and demand a fix.

  7. #7
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: whats the problem

    I have to agree with the others that your system is slightly undersized and you could add more insulation. But this has been the hottest July on record and I expect August to be a little cooler this year so the worse is over, and 79 isn't all that bad. I'd say leave things alone.

    If you want more comfort, install ceiling fans. We are running in the high 90's and low 100's here and I keep the thermostat at 81. With the fans on high, it is comfortable. I do have a small window air unit in the bedroom as I like it down to around 74 when I sleep. I turn it off when I go to bed so I don't have to listen to it all night and turn it on around mid afternoon or early evening.

    BTW, is you central air running full time or is it cycling? If it is cycling, you may need to get it serviced.

  8. #8
    Join Date
    May 2011
    Posts
    251

    Default Re: whats the problem

    Will it cool to 75F when it's 90F outside? Are you keeping it at the same temperature all day or using setbacks Design temp in most of New Jersey is only 89-91F. At 95F it should only hold about 77F indoors.

    Are most of your blinds closed? Especially on the south and west?

    Sounds like it's sized almost perfectly. Better to be slightly undersides than oversized. Long run times make a system keep humidity lower and run more efficiently. It takes 8-10 minutes to reach maximum effceincy. The systems in many homes rarely run more than 15 minutes at a time.

    I agree that adding insulation may help. Sealing up air leaks will help the most. Door seals, storms doors, window seals, sill plate, and most important, any penetration into the attic. A larger unit will be noisier, use more energy and not remove humidity as well.

    FYI - design temperature in Florida is no higher than where I am in SE Iowa... only the humidity is slightly higher... and it stays warmer year round in Florida...ie you have no winter.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  9. #9
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: whats the problem

    Houston is the most air conditioned city in the world. Its not hard to keep a bowling alley at 70F so the bowlers aren't sweating. The spouses who come to watch bring sweaters in the summer.

    Our highs normally run just under 100 with night temps dipping into the low 80's. Humidity.... lets just say there isn't a need to lick a stamp, you just wave it around for a spell. My barely insulated house built in 1920 has a 3 ton unit for 1100 sf. We keep the house at 77F and use ceiling fans when we are in those rooms.

  10. #10
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    128

    Default Re: whats the problem

    Age of the house will have a lot to do with the insulation, check that first. Meanwhile, ceiling fans or oscillators in the rooms will serve to move the air and help you feel cooler.

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