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  1. #1
    Join Date
    Sep 2008
    Location
    Dallas FortWorth Texas
    Posts
    3

    Rule of thumb: Sq Ft per ton of A/C

    Does anyone know where I can find a Rule of Thumb on how many square feet of per ton of A/C for different commercial/Industrial applications? Specifically an older bowling alley. I've seen a list before but can't find one.

    This is my first time ever using a forum. Hi hopes.

  2. #2
    Join Date
    Jan 2007
    Posts
    23
    Do yourself a favor and do a heat load calc or hire a contractor who will. That way you will have the proper a/c unit for your application.

  3. #3
    Join Date
    Dec 2007
    Posts
    13

    Sq foot per ton of AC

    2nd thought getting heat load calc. for comm. building

  4. #4
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    1,948
    RS Means has some 'rule of thumb' for sq ft per ton. But since they don't say what climate they apply to I think they are a way to get yourself in trouble. Just how many bowling alleys in Alaska need A/C anyway? About the same amount of heat as a bowling alley in Miami?
    If "I have always done it this way" is a good reason to do it again, how many times do I have to do something wrong - before it becomes right?

  5. #5
    Join Date
    Sep 2007
    Location
    SF Bay Area
    Posts
    130
    Use the old standards:

    400cfm/ton
    ¾ -1½cfm/sqft interior, well insulated
    1½ - 3cfm/sqft depending on exposure, windows

    -or-

    Do it right and follow jrbertalot's advice, do a load calc.

  6. #6
    Join Date
    Mar 2003
    Posts
    7,314
    Its a trick question, there are just too many variables to actually use something like that. If you do, prepare for callbacks.

  7. #7
    Join Date
    Jul 2007
    Location
    Eastern Shore of Virginia
    Posts
    108
    Quote Originally Posted by flange View Post
    Its a trick question, there are just too many variables to actually use something like that. If you do, prepare for callbacks.
    And take a lot of notes they maybe good for your lawyer when the case gets to court.

  8. #8
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,397
    You really can't use the rule of thumb. You are going to have different areas with different loads. Such as a kitchen with a lot of cooking equipment. You will have to account for make-up air for vent hoods depending on the rated CFM for the vent hood(s). A game room will need more air for heat put off by video games than the bar area. Lots of factors going into sizing.

  9. #9
    Join Date
    Sep 2007
    Location
    SF Bay Area
    Posts
    130
    I re-read the OP. What you are probably referring to is a table from the ASHREA Fundamentals hand book. They list ventilation requirements and heat gains for bowling alleys, hospitals, cafeterias, etc...

    Mechanical engineering reference books also have this kind of info.

    You can download Loren Cooks' "Mechanical Cook Book" here. (It's a .pdf)

    Try ASHREA's web site or Google.

    You've obviously got the "internet", try ASHREA's web site or Google.

  10. #10
    Join Date
    Nov 2004
    Location
    North Florida/South Georgia
    Posts
    983

    Oh boy,

    Against my better judgement I will add something to this.

    Besides, I can't sleep.

    Here in north Florida we heard 500 sq ft per ton tossed around for years. Then in the 90s, we were all told you could figure 600 sq ft per ton if the house had good insulation & if you used a "high efficency" unit.

    Pretty vague huh.?

    The only "rule of thumb" I've seen that I liked (just a little) was cubic ft X 3 = the BTU requirement.

    In other words:

    sq ft X ceiling height = cubic ft. So, cubic ft X 3 = BTUs needed.

    I only like it because it has a little bit of science to it & believe it or not, it's been close the the load calc more than once over the years.

    One more factor you can add for commercial sites: Humans = 600 BTUs per head & it can 900 BTUs per head if they are active, soulful church, dance hall, gym, etc.

    I don't want to hi jack the thread but I think it would more interesting to discuss where the term "rule of thumb" came from.
    All my leon freaked out!

  11. #11
    Join Date
    Mar 2003
    Posts
    7,314
    In my heritage classes, it was told to me that in the old days of a certain country, if you were longer than your thumb, you could indeed, rule the household. If not, your wife was the ruler.

  12. #12
    Join Date
    Nov 2004
    Location
    North Florida/South Georgia
    Posts
    983

    Thats funny

    So in the future when we see guys that have wives running the house, we can assume, hmmmmmm..........




    Actually, I always heard it was from the dark ages when men would discipline their wives & the law allowed the men to use a stick no larger than his own thumb.



    I'm glad times have changed because I'm pretty sure my wife would kick my a$$ if I hit her with a stick.
    All my leon freaked out!

  13. #13
    Join Date
    Sep 2008
    Location
    Dallas FortWorth Texas
    Posts
    3

    Got what I'm looking for from you guys

    Thanks all for the feedback.

    The rules of thumb you guys gave, especially Chiller Mekanik & HeatXfer, should give us a good starting point for a discussion with my customer.

    I know we will need to do a load calc if the customer decides to explore that route (capital expenditures).

    It's nice to see that this forum has helpful & resourceful people on it.

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