Guidelines to Air Condition Sizing

This belongs in the mechanical engineering area http://cr4.globalspec.com/section/mechanical-engineering

Factors to consider when sizing an air conditioner unit:

Cubic feet of interior space
Maximum number of anticipated occupants, including the dogs
Engine displacement

Most people buy a car with the air conditioner already installed.

Oh, it's not for your car? Then will you tell us what this air conditioner is for?

its for office buildings, the window type air con.

Whichever guidelines you use, remember that they are just that....guidelines.

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Adjustments need to be made for the specifics of your situation....

In addition to square footage and number of occupants, you could consider the following:

-What is the normal yearly high temperature for the location?

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-Does the area have high humidity?

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-It the building relatively free of leaks/drafts?

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-Is the building shaded from mid day sun?

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-Are there overhangs on the east and west sides of the building?

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-Orientation and treatments of windows and doors?

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-High ceilings?

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-How much traffic is expected through the office? How much exchange with outside air is caused by ingress egress?

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- How much electricity is used in or immediately adjacent to the office? Fax machines, copiers, monitors, refrigerators, cooking appliances...all are additional heat loads to be considered.

thank you very much for the clarification........its now more clearer because, i was using the guidelines as they were........thanx

This is easily found by searching:

1. How to Size a Central Air Conditioner | eHow.com
   

Properly Sized Room Air Conditioners - Home : ENERGY STAR

1. 
   Simple Guide to Air Conditioner Sizing
   

1. Selecting Air Conditioner Size - Alpine Home Air Products ...

Thank for the link lyn,..the real problem iam having is that....if i u all these different methods...the sizes differ, some with big variances.......how then do i gauge which formula to use.

OK,

Air conditioners are sized by tons of cooling. 1 ton of cooling is equal to 12,000 BTU/hour.

So, using the Energy Star web site, I'd estimate the size of the room and go with unit that comes close to that figure in tons. Most units are sized in 6,000BTH increments, so you might find that a 2 1/2 ton unit will suit your needs.

If you plan to buy multiple units the seller will probably be glad to assist you with sizing the units.

You need to run a heatload calculation...The air-conditioner size varies according to location and personal preference....Generally speaking here in Florida, 1 ton per 400-500sqft, or 1 tone per bdrm rule of thumb...A pro can size a house just by looking, if you want to be sure, get a pro...

Commercial space 350sqft per ton...

A pretty good way to size up is ( in meters, as everything should be ) length by width by 2.5 x 205.

This will give you a btu indictaion that is pretty accurate. Normally just go to the next model up from the btu calculated and this will account for most other loading issues you may encounter. (and make sure they aren't mounted too low or too high)

Do yourself a favor and get your hands on the 2011 ASHRAE HVAC Applications Handbook. Chapters 14 through 18 will give you the guidance you are looking for. You will have to consider ever source of heat gain, internal and external. The infomation in the Handbook will give you the guidlines you are looking for.

Good luck.

Lou Bindner

Lots of great suggestions so far, Rule of thumb 400 sq ft per ton - you a desk - fluorescent lights - 1 computer and monitor - and window with the door closed. Be sure there is a small amount of OSA in the unit (window shaker) you choose for proper air changes.

Any more than that load calculations, specific heat, latent heat will need to be known or shoot from the hip at 350 sq ft per ton which was the calc decided a few years ago before more efficient lighting came into play.

Ther is really so much to consider your best bet is to hire a Professional in your area that knows the ambient climate, room placement to the suns travels, humidity levels...etc.

Thanks very much guys...you have been very helpful...greatly appreciate yo responses