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What It Means to “Size” an Air Conditioner


It’s time to get a new air conditioner for your home. Great, you’ve come to the right people to help you with your central AC installation in Greenville, SC. We’ve got the NATE-certified technicians who can do the job right, starting with sizing the unit and…

Wait, what does “sizing” mean, you ask? Good question! Understanding what it means to “size” an air conditioner and why it’s so important will tell you plenty about why it pays to work with the best licensed HVAC professionals around.

An Air Conditioner’s “Size” Isn’t How Large It Is

Although it may sound as if “sizing” an AC means finding a unit that will fit in the available place, that’s not what it means at all.

What “size” means in this case is the cooling capacity of the air conditioner. In other words, how much cool air it can push out, or the AC’s “cooling power.” To make an easy comparison, think of how much cooling you get from a window air conditioner: enough to cool a medium-sized room. Would this same level of cooling work for a whole house? Not at all! You’d need an air conditioner with a much larger cooling capacity. 

Measuring AC Size

The cooling capacity of an air conditioning unit is measured as the amount of BTUs (British Thermal Units) of heat the AC can pump out of a space in an hour. Because BTUs are small units, they’re grouped together in units of 12,000 BTUs, which is known as a ton. (Why a ton? Because 12,000 BTUs is the amount of heat needed to melt one ton of ice over 24 hours.)

This can also be a bit confusing to people because these tons don’t measure weight. When you hear technicians talking about a 5-ton air conditioner vs an 8-ton air conditioner, they don’t mean how much the system weighs. 

The Sizing Process

Most central air conditioning systems for homes are between 2-8 tons. To find out the right size AC, technicians perform a heat load calculation that combines factors like the square footage of the building, the insulation levels, the number of heat-generating appliances, the number of residents, the number of windows, the direction they face, etc. When the technicians complete the calculation, they’ll know the tonnage necessary for a new AC. 

Why Sizing Must Be Accurate

If the wrong size air conditioner is installed in a home, it’s bad news! An air conditioner that’s too small won’t provide enough cooling power to make the house comfortable. It will instead run incessantly, wasting power without delivering comfort.

But an oversized air conditioner is just as bad because it will short cycle: shut off early before completing a cooling cycle and then turn back on again a short time later. The continual stop-start of short cycling is also a massive energy waste, and it wears down an AC much faster so it fails years too early. 

You can trust that our team will accurately size your new AC so you’ll get many years of energy-efficient and effective performance from it. 

Contact Carolina Climate Control when you need the best in new HVAC installation. The Moose Is Loose in Your Neighborhood!

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