Fall is upon us, but this is a great time to take advantage of discounted prices to replace your air conditioner if you need to. All too often I see HVAC that is not properly sized during inspections. The first thing you should do is to determine the square footage of your home. The second would be to make sure you get the proper size unit for that square footage.
Air conditioners are sized by the ton. There are 12,000 BTU's in a ton, so a 2 ton unit would have 24,000 BTU's.
Here are the recommended tons per square footage for the Kansas City area:
1.5 tons = 600-1000 square feet
2 tons = 1001-1300 square feet
2.5 tons = 1301-1600 square feet
3 tons = 1601-1900 square feet
3.5 tons = 1901-2200 square feet
4 tons = 2201-2600 square feet
5 tons = 2601-3200 square feet
When buying a unit it is important not to buy one that is too large. A system that is installed that is too large for the space will short cycle (the compressor will not run long enough to dehumidify the space to your comfort level). It will also operate more frequently, resulting in higher operating costs and shortening the life of the unit.
For heating, it's recommended that we have 40-45 BTU's per square foot here in Kansas City. Use the lower number if your home is well insulated and the higher if it is not. For example, if your home is well insulated and is 3000 square feet, your calculation would be:
2000 sqft X .40 = 80,000 actual BTU output.
Next step would be to find out your gas furnace output. To do this you would multiply it's efficiency rating by it's listed input rating for the BTU output of heat. For example, if a furnace has an actual input rating of 100,000 BTU's and an efficiency rating of 80% it will be:
100,000 BTU input X .80 efficiency = 80,000 actual BTU output
So if you have a 2000 square foot home with a 80% efficiency rating, you will need a 100,000 BTU input furnace to produce the 80,000 BTU's output of heat.
This may all sound confusing and if so, contact a qualified local HVAC contractor to ensure you have the properly sized air conditioner and furnace in your home.
Devereaux Van Dyne, Certified Professional Home Inspector