October 8, 2016

Purchasing a system that is too large for a home is wasteful both in the initial investment and in the cost of utilities. But making the mistake of purchasing a system that is too small for a house means that you will struggle to heat it in the winter and cool it in the summer. It just won’t keep up with the demand, because it cannot process air fast enough to cool the whole house.

Choosing the correct size HVAC system is as simple as following about 5 steps. That being said, it is usually best for a trained professional to assess the size need for your home, as these steps are somewhat tedious and may be daunting. But at least you can get a general idea.

The first step is to purchase Manual J by the Air Conditioning Contractors of America. This manual helps you calculate the cooling needs and heating needs based on a complex set of calculations including size, type, and location of windows, and even certain appliances (which produce heat).

The second step is to download a copy of the Air Conditioning Contractors of America’s Speed Sheet Excel worksheet. This makes those complex calculations easier. Third, plug in all the measurements of the windows and doors, etc. You will also need to enter the latitude and elevation of your geographical area.

Fourth, take the total square footage of your home (and if you don’t know it, measure it) and then divide that number by 600 for the air conditioning size in tons. The Weather Channel states that homes need one ton of air conditioning for every 600 square feet.

Finally, if all else fails, just use the size of HVAC that is currently in the home as a judgment. That is, however, unless you have found that the current system just never seemed to be able to properly heat and/or cool the house which may indicate that the last person to put one in did not do due diligence to ensure the correct size.

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