How do you determine what size central air unit you need for your home?

Question

I was told several years ago that you need 1 ton for every 600

square ft. of finished space in your home. Someone please let me know about this, THANKS

Answer 1

i would count the rooms, then as a rule it will take 8,000 btu,s to cool that room, so 8,000 btu per room  times  other rooms,

Answer 2

That is probably a rule of thumb for an average home in your area and may be close.

The proper way is to get measurements of the home including window sizes and insulation values and have a heat gain calculation done.

This is typically done by the professional HVAC contractor and is done when they come out to give you a quote or estimate.

Answer 3

Vaulted ceilings,extra windows,etc.will make a difference from the norm but  500 sq ft per ton is average.

Upsizing the indoor unit by 1/2 ton only, larger than the outdoor unit will provide better cooling and extra latent (humidity) heat removal.

Answer 4

1 ton for every 4-500 sq ft is the rule but it depends on how well your insulated what kind of walls, windows, doors etc.you have it also depends on your region, if you currently have an a/c I would go by that if you were satisfied/ unsatisfied or check with your neighbors with similar homes

Answer 5

The best thing to do with a "rule of thumb" is to stick that thumb where the sun don't shine.

An accurate measuring of the house, rooms, windows, doors, insulation and taking into account exposure directions then using Manual J the load can be determined properly.

Then the ducts need measured and the blower capacity needs checked so corrections can be made as needed for proper air flow.

Upsizing coils in today's equipment can cause nightmares.

Systems should be installed as to manufacturers specifications and ARI ratings. Otherwise efficiency will suffer, and performance can be very poor.

The "rule of thumb" and "wing it" method is for JACK LEGS, or HACKS as we call them around here.