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Thread: Unit Size

  1. #1
    Join Date
    May 2005
    Posts
    1
    Am replacing a 3 ton ac. Have gotten 3 estimates with three differing recommendations on tonnage - 2.5 T, 3 T , and 'you need a 2.5 ton but a 3 ton is ok'. No load calculation has been done. Will a 3 ton result in problems associated with an oversized unit or can I get the 3 ton and still get good dehumidification and no short cycling problems? The Trane unit I want comes in a 3 ton but not a 2.5 ton. (I'm locked into Trane so moving to another brand is not an option. I can only move to another Trane model.)

  2. #2
    Join Date
    Oct 2002
    Location
    Mahopac NY
    Posts
    448
    You would be smart to have a load calculation done. Why are you "locked into" Trane? Your comfort will depend on how oversized a three ton may be. The only way to know is a load calc.
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  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,100
    Since no load calc was done, maybe what your house needs is 2.25 ton, so 2.5 would be ok, but 3 ton might not dehumidify enough for you to be comfortable.

    In other words, have a load calc done, click on the bulls eye, and you can do it yourself.
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  4. #4
    Join Date
    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    A load calculation is the best way to decide,but if you don't get that done follow this;

    If you have lived in the home,thru HOT summer(s),and it kept you comfortable,then you don't need a larger system.If it doin't run a lot on hot days it may be too large.

    If you need a larger system ,the duct system is likely too small to handle it,you need a real Pro,to tell you.That should include checking the External Static Pressure,so ask about it.

  5. #5
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Selections Available

    Originally posted by ransdell
    ... and 'you need a 2.5 ton but a 3 ton is ok'.
    The Trane unit I want comes in a 3 ton but not a 2.5 ton.
    If your house is < ~1700 Square feet with < ~ 250 Square feet of glass ( no location/state given), the 2.5-ton should likely be selected.

    You may wish to try review the XL15i model which is now available and may meet your budget.

    http://www.trane.com/Residential/Pro...ers/XL15i.aspx

    XL16i with 2-stage compressor and Variable Speed Air Handler 4TEE3F037 ( or similar) may suit you also.

    http://www.trane.com/Residential/Pro...ableSpeed.aspx

    racingdanr11@comcast.net if you wish a more specific review
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    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  6. #6
    Join Date
    Apr 2003
    Location
    Iowa
    Posts
    763
    the XL16i doesn't come in 2 1/2 ton.

  7. #7
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    Originally posted by airconman
    the XL16i doesn't come in 2 1/2 ton.
    It doesn't, but with the correct coil match you may be able to get it to perform closer to a 2 1/2..
    Its all in your product data!
    How tall are you Private???!!!!

  8. #8
    Join Date
    May 2005
    Posts
    5
    1st we are talking about 4,000 to 5,000 btu's of additional cooling. If you aren't going to do a load calc (which your contractor should do on every sales call) and humidity levels in your area are high. Consider a 2.5 ton with a variable speed indoor unit. This will give you a little higher BTU rating and remove more moisture as the fan speed starts off at a much slower speed (each time it cycles on) and pulls more moisture because of operating with a colder coil. Less sensible heat is initially removed and thus greater indoor comfort.

    Mfg's have charts that show what their equipment can do both sensible and latent at a given indoor temp.

  9. #9
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    should have a load done to know for sure what you need
    any true contractor should not have a problem doing one
    with out a load done
    since you have a three ton unit in now and are replacing it with a new one with out a load man-j done and it has praformed well over the years then but the same back
    man-j may show it is the correct size and may show you need a smaller one this is why it is so important to do.
    guessing is not the proper way to size an ac system properly. in jersey you will need a manual-J IN ORDER TO RECIEVE A REBATE with out it no rebate
    so tell your contractors you want it done so you know you have the correct size unit installed

  10. #10
    Do things right.Stop the guesswork and get the load done.
    A load calculation not only should be done, in some states it must be done.
    Unfortunately, many localities do not require the load calc when a replacement job is performed.
    Then you can have someone check duct sizing.
    Then, equipment sizing.
    Anything less is unacceptable.

  11. #11
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,005

    Re: Selections Available

    [QUOTE]Originally posted by dan sw fl
    [B]
    Originally posted by ransdell
    ... and 'you need a 2.5 ton but a 3 ton is ok'.
    The Trane unit I want comes in a 3 ton but not a 2.5 ton.
    If your house is < ~1700 Square feet with < ~ 250 Square feet of glass ( no location/state given), the 2.5-ton should likely be selected.

    You may wish to try review the XL15i model which is now available and may meet your budget.

    Wayyyyyyy to funny. How do u come by this when you dont even know what the outdoor or indoor design temps are??????
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  12. #12
    Join Date
    Jul 2008
    Posts
    17
    A proper manual J heat load calculation is the only way to really know the size unit you need. If a load calc is not done your only guessing.

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