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  1. #1
    Join Date
    Aug 2008
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    79

    using square foot per ton basis

    Are things changing so much that 600sqft per ton is not the standard for A/C any more? I know I am not taking in account the load calculation but I here of so much undersizing going on based on the SEER that in my thinking I thought that the SEER is only dealing with current usage. (Seasonal Energy Efficiency Rating) If an individual had a 2.5 ton 8 SEER it would be replaced with a 2.5 13Seer because the home insulation has not changed. An inquiry would be appreciated.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,189
    It never was a "standard" as construction quality and amount of windows varied as did outdoor temp. Around here, 600 sq ft/ton might work, in Arizona where they don't build the houses, especially older, like we do, might take twice that.

    Only answer is an accurate load calc.

  3. #3
    Join Date
    Aug 2008
    Posts
    79

    square foot per ton

    I do not know about Arizona but I do not think that will work here in NC

  4. #4
    Join Date
    Aug 2008
    Posts
    131
    Here in (The Detroit area) the rule of thumb is 600sf per ton on old construction and 800sf per ton on new construction. Not allways accurate. Best is a heat load calc.

  5. #5
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    Quote Originally Posted by Gopirates View Post
    Are things changing so much that 600sqft per ton is not the standard for A/C any more? I know I am not taking in account the load calculation but I here of so much undersizing going on based on the SEER that in my thinking I thought that the SEER is only dealing with current usage. (Seasonal Energy Efficiency Rating) If an individual had a 2.5 ton 8 SEER it would be replaced with a 2.5 13Seer because the home insulation has not changed. An inquiry would be appreciated.
    Sqft per ton is useless.

    My 2 ton 14 SEER Trane heat pump cools my 4,000 sq. ft of house quite well.

  6. #6
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by pipefitter636 View Post
    Here in (The Detroit area) the rule of thumb is 600sf per ton on old construction and 800sf per ton on new construction. Not always accurate. Best is a heat load calc.
    Only hacks use those numbers. i am in the same area as you and don't know any independent who would stake their rep on those ambiguous numbers.

    Are you in service or the fitting end of 636?

  7. #7
    Join Date
    Jun 2004
    Location
    Howell, Michigan
    Posts
    16,176
    Square ft per ton.........hmmm..............let's use an example.

    2000 sq ft home divided by 750 = 2.67 tons.

    Now that house has an 18' great room ceiling, 10' ceilings everywhere else, tons of windows facing west, east and every which way, built in 1970, it just might need more than that.

    That's why we do load calcs.

  8. #8
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by HeyBob View Post
    Square ft per ton.........hmmm..............let's use an example.

    2000 sq ft home divided by 750 = 2.67 tons.

    Now that house has an 18' great room ceiling, 10' ceilings everywhere else, tons of windows facing west, east and every which way, built in 1970, it just might need more than that.

    That's why we do load calcs.

  9. #9
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by HeyBob View Post
    Square ft per ton.........hmmm..............let's use an example.

    2000 sq ft home divided by 750 = 2.67 tons.

    Now that house has an 18' great room ceiling, 10' ceilings everywhere else, tons of windows facing west, east and every which way, built in 1970, it just might need more than that.

    That's why we do load calcs.
    Robert just for kicks say there are no such thing as load calcs, what size does you hvac sense tell you?

  10. #10
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    Quote Originally Posted by paul42 View Post
    Sqft per ton is useless.

    My 2 ton 14 SEER Trane heat pump cools my 4,000 sq. ft of house quite well.
    that's a crock!



    ,

  11. #11
    Join Date
    Aug 2008
    Posts
    79

    Reply

    Quote Originally Posted by hvaclover View Post
    Only hacks use those numbers. i am in the same area as you and don't know any independent who would stake their rep on those ambiguous numbers.

    Are you in service or the fitting end of 636?
    Yes I am in service. I started out doing residential and now I am doing controls whether it is on the equipment or doing it through several types of BAS. I asked the question due to the reading I have been doing on this web site and other web sites and I have noticed the changes in sizing units verses what is generally taught in the classroom besides heat load calculations. Heat load calculations are how it should be done no doubt about it.

  12. #12
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by Airmechanical View Post
    that's a crock!



    ,
    yep assuming he had only a single furnace a two ton evap would restrictt the flow with out by pass dampers in the heat cycle.

  13. #13
    Join Date
    Aug 2008
    Posts
    131
    Quote Originally Posted by hvaclover View Post
    Only hacks use those numbers. i am in the same area as you and don't know any independent who would stake their rep on those ambiguous numbers.

    Are you in service or the fitting end of 636?
    I didn't say they were accurate did I!!! What did I say was the best method???

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