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  1. #1
    Join Date
    Aug 2011
    Posts
    8

    2.5 Ton vs 3.0 Ton

    I have a 1100 square foot house(excluding the garage).
    We currently have a 2.5 ton unit. We are looking to replace our current unit which was installed in 1994 due to not cooling when it's 100 degrees outside.
    Contracters are differing on 2.5 and 3. units. Does it really matter?

  2. #2
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    952

    Yes,

    it could matter. How often does it get 100 degrees in your area? If the system is oversized, it may not de-humidify properly. The important thing is not to size a system based on a few days of higher then normal temperatures.
    Last edited by gregp; 08-09-2011 at 10:51 AM. Reason: can't spell worth crap

  3. #3
    Join Date
    Oct 2004
    Location
    So Cal
    Posts
    3,502
    Yes it does.

  4. #4
    Join Date
    Aug 2011
    Posts
    8
    I live in Miami, Florida

  5. #5
    Join Date
    Aug 2011
    Posts
    568

    Cool

    Quote Originally Posted by Mary9921 View Post
    I have a 1100 square foot house(excluding the garage).
    We currently have a 2.5 ton unit. We are looking to replace our current unit which was installed in 1994 due to not cooling when it's 100 degrees outside.
    Contracters are differing on 2.5 and 3. units. Does it really matter?
    curious, on those 100 degree days, what temp, do you think the unit should get to, that would make you comfortable/happy? and on those 100 degree days what does your current system reach with the 2.5 ton unit?

  6. #6
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,974

    Arrow Do the testing to get the data first, on which to base decision on...

    Miami, FL, 2.5% summer design 90-F dry bulb, 77-F wet bulb 56% relative humidity.
    That figures to be a high 120.69 grs moisture per lb of air.

    In that humid climate, a Home Energy Audit should be performed with a blower door test.
    After any retrofit work, a manual J ought to be performed.
    With that high a humidity, the Infiltration Rate must be kept as low as possible.

    The duct system must be examined & airflow tested before selecting a new condenser & matching indoor coil.

    From that data, you & your contractor select the best combination of equipment & components that will work best in your climate, with your home, the final duct system & those humidity control needs.

    Good Luck...

  7. #7
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,903
    Quote Originally Posted by Mary9921 View Post
    I have a 1100 square foot house(excluding the garage).
    We currently have a 2.5 ton unit. We are looking to replace our current unit which was installed in 1994 due to not cooling when it's 100 degrees outside.
    Contracters are differing on 2.5 and 3. units. Does it really matter?
    Sorry, 3 tons is crazy for 1100 sq ft.

    If you really require that much cooling, fix the house and ductwork. Throwing larger equipment at the problem won't make it go away.

    Chances are that the ductwork isn't sufficient for the 1000 cfm a 2.5 ton unit needs to move, let alone 1200 cfm for 3 tons.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,084
    The duct system must be examined & airflow tested before selecting a new condenser & matching indoor coil.
    Chances are that the ductwork isn't sufficient for the 1000 cfm a 2.5 ton unit needs to move, let alone 1200 cfm for 3 tons.
    There's the answer.

  9. #9
    Join Date
    Jan 2008
    Posts
    2,004
    As others have stated, make sure your insulation is top notch, infiltration is at a minimum, duct-work is tight.
    Then put in a 1.5 or 2 ton, depending on manual J.
    Even 2.5 ton, in 100 degree heat, for 1100 sq ft is crazy.
    Also as stated here by someone very wise - insulation is something you pay for whether you have it or not.
    I have a 1000 sq ft rental, well insulated, with a 32 year old 1.5 ton A/C.
    It performed wonderfully when we recently hit 99 degrees. Renter was never uncomfortable.
    Keep in mind, a smaller unit will run longer cycles, and therefore de-humidify very well, which is ideal for your climate. On the hottest days, it will run nearly non-stop. That is a good thing.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  10. #10
    Join Date
    Aug 2011
    Posts
    8
    78 degrees is comfortable

  11. #11
    Join Date
    Aug 2011
    Posts
    8
    We are having the electric company come in and perform a test on the ducts before we hire the contractor to install the unit.

    the outside model is:Bryant 126BNA03600/inside:FV4CNF003T00

  12. #12
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,974

    Lightbulb

    Quote Originally Posted by Mary9921 View Post
    We are having the electric company come in and perform a test on the ducts before we hire the contractor to install the unit.

    the outside model is:Bryant 126BNA03600/inside:FV4CNF003T00
    That is only ONE piece of the total data needed... listen to what the professionals & others have suggested on your thread...

  13. #13
    Join Date
    Aug 2011
    Posts
    568

    Smile

    Quote Originally Posted by Mary9921 View Post
    78 degrees is comfortable
    so how low is your existing system bringing the tempature on a 100 degree day!

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