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  1. #1
    Join Date
    Nov 2009
    Posts
    1

    Default New central air unit

    Need to replace broken 2.5 ton central air unit. It cools about 1400 square feet. Old unit is over 20 years old. We're in process of improving insulation and have had received a number of quotes for new units, although most want to install a 3 ton unit or another 2.5 ton unit. No one is willing to perform a manual J load calculation. We are looking to take advantage of tax rebates etc, so are looking for energy efficient models. We live in Baton Rouge, Louisiana and need help figuring out which brand to use, size of unit etc. Any advice?

  2. #2
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: New central air unit

    Actually rule of thumb is 400 sq. ft. equals 1 ton so you would be in the 3.5 ton range, that's without doing a load calc. which would include insulation, window type, doors, and other building mat. I suppose that if a load calc were done and you had adequate ins., energy efficient windows, and insulated doors it could be brought down to a lower size.
    More than likely you only have an 8 or 10 seer unit so if you change out the Condenser you will have to change out the Air Handler or Coil as well. If you only change out the Condenser you won't get the proper seer rating and it's possible you could have equipment operating problems. Never mismatch units with diff. seerage, 10 seer with 10 seer, 13 seer with 13 seer etc. There has to be someone down there that will do a load Calc. Keep checking, never have someone just swap out a furnace, boiler or, A/C unit without having one done. without even doing a load calc. it sounds like it's undersized to me, especially since your in Louisiana and are cooling a 1400 sq. ft. home with a 2.5 ton System. When it was running did it run constantly, non stop? If it did then it was undersized.
    Best models to go with are Trane, Carrier, Bryant, some people say to stay away from Goodman but they have come a long way and at one time were at the bottom of the list. As for me, I have a 2.5 ton Trane that's been keeping this house cool for the past 25 years and runs like a top with routine Maintinence and not one major issue. Good Luck!!!
    Last edited by Sten; 11-26-2009 at 11:54 AM. Reason: miss spell

  3. #3
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: New central air unit

    Quote Originally Posted by col BR View Post
    Need to replace broken 2.5 ton central air unit. It cools about 1400 square feet. Old unit is over 20 years old. We're in process of improving insulation and have had received a number of quotes for new units, although most want to install a 3 ton unit or another 2.5 ton unit. No one is willing to perform a manual J load calculation. We are looking to take advantage of tax rebates etc, so are looking for energy efficient models. We live in Baton Rouge, Louisiana and need help figuring out which brand to use, size of unit etc. Any advice?
    A 2.5 ton A/C will be more than enough. This assumes that the home has some insulation, decent windows and not a flat roof. LOL

  4. #4
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: New central air unit

    Quote Originally Posted by Bob Gabrilson View Post
    A 2.5 ton A/C will be more than enough. This assumes that the home has some insulation, decent windows and not a flat roof. LOL
    You can say this with out doing a load calc???

  5. #5
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: New central air unit

    Quote Originally Posted by Sten View Post
    You can say this with out doing a load calc???
    All day long.

  6. #6
    Join Date
    Jul 2009
    Location
    Northeast
    Posts
    661

    Default Re: New central air unit

    LOLOLOLOL ***, your good

  7. #7
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: New central air unit

    Thanks, Sten. 37 years in the HVAC business. I'm not perfect (so my wife tells me). And we don't know all the facts, of course. I would rather unersize than oversize. My house, built in 1946, 2 story cape cod, poorly insulated (the best I could do, however) Iowa with high humifity, absolutely terrible windows (my wife won't let me change them), east/west exposure and it cools easily with a 2.5 ton on a 105 degree day. The house is 2250 sq. ft. Granted, I have shade front and back (big help). Go fiqure? Would I normally size like that? Not on your life.

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