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leonbowen
08-11-2010, 07:54 AM
I've been trying to find out how many tons of a/c needed for a given amount of living space. Is it LxWxH=cubic ftx number of air changes divided by 400?

youarerelevant
11-02-2010, 01:12 PM
There is no way to know that info without a load calculation. Every location and structure has different internal and external heat gain loads.

fearlessfurnace
11-02-2010, 01:36 PM
yeah its realy the square footage of outside sufaces, insulation values, and outside tempatures

k-fridge
11-02-2010, 02:06 PM
Moved to residential HVAC forum.

dave1234
11-02-2010, 03:31 PM
::DD: This is my favorite load calc method as per another member in a similar thread

Originally Posted by dijit
I just usually look and see how many ton's their trucks add up to be and multiply that number by 3. If they have a 1 ton truck in the driveway, then you use a 3 ton unit. If they have two 3/4 ton trucks in the driveway, then you install a 4.5 ton unit. But I never exceed the maximum weight rating for the roof. Because duh, you can't install a 5 ton unit on a roof that is only rated to support 3 tons of dead weight. In that case, you need to use a split system. Because you can put 2 3 ton dead weight trucks on a bridge that can hold 5 tons, but not one 6 ton truck. That is maximum per truck.

At least that is what we do for ACs out here in the desert. Maybe a furnace is different.

For a second story, multiply by by 1.8 and add 3200 lbs. Or is it subtract 3200 lbs? It don't matter, it'll work either way.

Oh wait, that is the rule of dumb not thumb.

EugeneTheJeep
11-02-2010, 03:36 PM
I've been trying to find out how many tons of a/c needed for a given amount of living space. Is it LxWxH=cubic ftx number of air changes divided by 400?

If you live in a glass house it might work? If you live in a Styrofoam box, no way. Maybe you should get one of the heat loss/gain tape measures like the big companies use?

jpsmith1cm
11-02-2010, 03:42 PM
There is no way to know that info without a load calculation. Every location and structure has different internal and external heat gain loads.

This is the best advice you've been given.

bwalley
11-02-2010, 04:53 PM
I've been trying to find out how many tons of a/c needed for a given amount of living space. Is it LxWxH=cubic ftx number of air changes divided by 400?

I have a room in an office building that is about 800 square feet, we were going to put a 3 ton unit in it, but I am thinking about going to a 5 ton unit, do you think there is a square footage formula for that?

11-02-2010, 05:01 PM
I was taught to look at the drawings, make a fist, and cover the building. One fist covers one ton of cooling....lol....
bwalley, in Plant City, yeah, that should be fine.. unless you have big hands. Have some strawberries for me in March at the Strawberry Festival!

NCtech
11-02-2010, 08:04 PM
Yes, there is really no way to know by sq ft. and be totally accurate. There are many variables, # of windows, type of windows, direction of windows, R-value of insulation, roof pitch and shingle type/color ect ect...

Someone needs to do a proper load calc on the space :callpro:

beenthere
11-02-2010, 09:14 PM
ROFL...

The OP is from back in August.

He didn't get an answer until today.

btuhack
11-02-2010, 09:15 PM
If you accept that 1 ton always covers 400 sf, then I accept that all cars get 35 MPG. Your 2000 SF house needs 5 tons and my jeep needs a tune up.

Your question isn't a bad one, just based on coarse ideas and if used, will provide sloppy results. If you poke around thru the threads posted, you'll find some interesting results that may help you decide what you really are asking about. Load calculations are an " estimate" and rely heavily on the accuracy of the values used. Garbage in, garbage out.

Good luck

bigtime
11-02-2010, 09:28 PM
700 ft2 per ton for a normal house (with no duct in the attic) is a pretty good rule of thumb in the southeast. A load calculation is just an estimate also. There are to many unknowns for it to be absolutely correct.

snupytcb
11-02-2010, 09:39 PM
ROFL...

The OP is from back in August.

He didn't get an answer until today.

at the rate his post count is going he will never make it to pro status.lol.