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  1. #14
    Join Date
    Apr 2004
    Posts
    7,680
    To the OP. The TXV will not be your problem it will still flow the correct refrigerant since it is looking at superheat. If it is drasticly oversized it can cause hunting which can make capacity and efficiency fall a bit but not have anything to do with your short cycling. If Carrier said that the match is fine then it is fine. If on the other hand you had an undersized valve then you would not be able to handle full loads as well.

    I think the right thing to do is to verify the airflow. If you are geting too much airflow you may actually increase the sensible capacity of the system which will satisfy the stat slightly faster. You may also watch the temps at the stat with a digital thermometer to verify you do not have a supply air register blowing on the stat which would also cause short cycling. Then consider the sizing with a manual J.

  2. #15
    3 ton txv is same for 2.5 ton no differance.

  3. #16
    Join Date
    Apr 2004
    Posts
    7,680
    Originally posted by bernm
    "400 sq ft per ton will cool most houses. It just won't dehumidify them."


    Hey, beenthere, are you saying that we should use less than 400 sq. ft. per ton in figuring our a/c size?
    No, I think he's saying dont use the rule of thumb at all. Your possible suggestion of using less than 400 would make it even worse.

  4. #17
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,793
    Originally posted by docholiday
    Originally posted by bernm
    "400 sq ft per ton will cool most houses. It just won't dehumidify them."


    Hey, beenthere, are you saying that we should use less than 400 sq. ft. per ton in figuring our a/c size?
    No, I think he's saying dont use the rule of thumb at all. Your possible suggestion of using less than 400 would make it even worse.
    NO, what Doc said.

    Do a load calc, and see what the house really needs, and your humidity will be much better.

    Over sizing just makes people set their stats lower to fell comfortable.
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  5. #18
    Join Date
    Jul 2005
    Posts
    4
    Thanks, that what I thought. I posed the question because of the mention of 400 sq. ft. per ton. I have heard every square footage per ton to use from 500 sq. ft. to 750 sq. ft. I hadn't seen anything below 500 sq. ft. except for commercial cooling.

  6. #19
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by bernm
    I have heard every square footage per ton to use from 500 sq. ft. to 750 sq. ft.
    Personally, I like 1000 square feet per ton. It makes it really easy to get rid of those surplus 2.5 T systems from my local warehouse.

  7. #20
    Join Date
    Apr 2004
    Posts
    7,680
    Travis has a point, if your going to use a rule of thumb, at least toss a little convienince in there for yourself.

    I think 1.5 tons will do it because the equipmetn costs less.

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