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Not Too Small, Not Too Large: Why AC’s Must Be Just the Right Size

Air-conditioner-repairmanWhen it comes to the size of an air conditioner in a house, the “Goldilocks Rule” applies: you don’t want an air conditioner that’s too small or too large, but one that’s just right. Finding the right size of air conditioner is a tricky job, however, and it’s not something you want to make a guess at. You must have skilled professionals handle the job of sizing a new central air conditioning installation so you don’t end up with either an AC that can’t keep your home cool enough or an AC that drains energy because it’s too powerful.

What “size” means when it comes to an air conditioner

“Sizing” an AC makes it sound at first as if we’re looking at how physically big the system is. But what we’re really talking about is the cooling capacity of the air conditioner. To make it a bit more confusing, the cooling capacity is often referred to as “tons.” But it has nothing to do with how much the system weighs!

In HVAC terms, one ton of cooling is equal to removing 12,000 BTUs of heat from a home in an hour. (This is the amount of heat necessary to melt one ton of ice, which is where the name ton comes from.) Most homes will use an AC between 1.5 and 5 tons. HVAC professionals perform a heat load calculation to determine how many tons of cooling is necessary to provide comfort without turning into an energy waster. The calculation takes factors like the number of windows in the home, the amount of heat given off by appliances and people, and the insulation in the walls and attic, and uses them to determine how powerful a new AC must be.

Why going too large is as much a problem as going too small

You can probably guess why having an undersized AC is going to cause trouble. If your home requires 4 tons of cooling to keep all the rooms at a comfortable temperature, a 1.5 ton air conditioner just won’t cut it! The AC will run constantly trying to reach its set temperature, and the house will be too hot.

But why is oversized a problem? Can’t the AC just be turned down lower? Why not simply put in a 5 ton air conditioner if you can afford it?

The problem from an oversized AC is that it can’t simply be “turned down lower.” Air conditioner compressors turn on and run for as long as necessary to reach their temperature setting. An oversized AC will register too early that it’s reached its temperature goal and shut off the compressor before completing the cooling cycle. The compressor will then turn back on a short time later, then shut off again, and over and over… This is called short-cycling, and it’s absolute murder on an air conditioner’s parts. It wastes energy and leads to the system needing to be replaced early.

You can trust to our air conditioning experts in Staten Island, NY when you need to install a new central AC or replace an old one. Contact us today and we’ll get you started on the road to the AC that’s just right for you.

Bob Mims Heating & Air Conditioning has served Staten Island’s heating and AC needs since 1955.

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