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Proudly Serving the Conway Area

Proudly Serving the Conway Area


Dewees HVAC Blog

Sizing an Air Conditioner: Why This Job Is So Important


When it’s time for a new air conditioning installation in Conway, AR, what are the most important steps to take? The first we recommend is calling our technicians to help with the job. Having professionals with you from the start will make the other steps easier because you can trust the experts to know which one to take and how to do them correctly.

Few steps are more important for installing a central air conditioning system than sizing it. We don’t mean determining how physically large the air conditioner is, but rather its cooling capacity. Sizing isn’t a guesswork job—it requires precision, otherwise your home will end up with a system that won’t work right and will rapidly drain money.

How AC Size Is Measured

If you’ve looked at the stats for window air conditioners, you’ll see their cooling capacity listed in BTUs, or British Thermal Units. One BTU is the amount of heat necessary to raise the temperature of a pound of water by 1°F. (If you want the full technical specs, 1 BTU = 1,055 joules. Now you can impress your friends.) The BTUs for a window AC is the amount of heat the unit can remove from a room in an hour. Window units have capacities from 5,000 to 12,000 BTUs.

Central ACs have much greater cooling capacities because they have a larger volume of space to condition. Rather than use BTUs, the measurement for these units is tons. One ton equals 12,000 BTUs. Most homes will require an air conditioner of at least 5 tons. 

The Oversized and Undersized AC Problem

What will go wrong if your home has an AC that’s underpowered (undersized) or overpowered (oversized)? 

  • Undersized: The air conditioning system cannot remove enough heat from the house to cool it down to the comfortable temperature people need. The AC will run in long cycles as it struggles to reach a temperature that’s out of its range, resulting in massive power waste and the system running down. The house will remain too warm.
  • Oversized: It’s easy to think that erring on the side of too big isn’t that much of a problem. But it is! An oversized AC will short-cycle, meaning it will turn on and off rapidly because it lowers the indoor temperature too rapidly. This drains power and puts enormous stress on the system, leading to an early replacement. The house won’t receive even cooling because the system will continue to shut down too early.

How We Size Your New AC

The way we found out the proper tonnage of your new central air conditioning system is to perform a load calculation for your house. This calculation uses various factors about the house: its size, the number of people in it, how well it’s insulated, the amount of heat given off by lights and appliances, the number of windows and the direction they face, etc. We’ll find the precise size necessary for your new AC to perform exactly the way it should.

Dewees HVAC proudly serves the Conway area. Call us for air conditioning installation and other AC services—we’re here to keep you comfortable!

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