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Does It Really Matter What Size AC I Get?


When you start to consider your AC installation options in Portland, OR, you’ll run up against several questions: Should you get a high-efficiency air conditioner? Maybe switch to a heat pump? Or go for special features such as a scroll compressor? One question that may occur to you is how big an AC you need, and whether it’s important or not if you end up with one that’s on the larger side.

To clarify: when we talk about the “size” of an air conditioner, we don’t mean the physical size or how much size it takes up. We mean the cooling capacity of the AC system, how much heat it can remove from the air. AC size is measured as “tons,” with 1 ton equal to 12,000 BTUs of heat removed an hour. (For a point of comparison, a window AC removes about 5,000 BTUs/hour, just enough for a single room.) Standard residential central air conditioners range from 1 to 5 tons of cooling power.

AC Size Is Critical!

To get to the basic question, it matters a great deal what size air conditioner you have installed. Obviously, an AC that’s too small is a problem because it won’t deliver the cooling the house needs, and the system will run and run without stopping as it tries to reach a temperature setting out of its capacity. For example, putting in a 1 ton AC for a three-bedroom house is a no-go. That 1 ton AC might handle a small, open plan home, but not anything larger. 

But why not pick an AC that’s as large as you can afford? That way you’ll be able to beat the heat no matter what, and you can always turn it down lower when it gets too cold.

Unfortunately, air conditioners don’t work this way, and this line of thinking has gotten many amateur installers into trouble. 

Here’s why the oversized air conditioner is bad news: The system will lower the temperature at the center of the house so rapidly that the thermostat will incorrectly register that the AC has finished its job and shut it down early before it completes the necessary cooling cycle. The thermostat will then turn the AC back on again a short time later and repeat the process. HVAC technicians call this short-cycling, and it puts immense strain on an air conditioning system, leading to a shortened service life, while at the same time driving up utility bills because of all the energy that goes into starting the system multiple times. (An AC consumes the most power when it starts the compressor.) 

Finding the Right Size AC

To find the right size of AC for a house, leave the work to professionals. Our technicians will perform a load calculation for your house to factor together various criteria (house size, number of windows, heat-producing appliances, insulation, etc.) to determine how much cooling the building requires. We then match you with an AC that has the correct tonnage, and you’ll live comfortably for many summers to come.

Work with Clawson Heating & Air Conditioning when you need a great new air conditioning system in the Greater Portland Area. “Connecting People to Comfort!”

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