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Serving the Treasure Coast


Serving the Treasure Coast


Mechanical Air Conditioning Blog

Sizing an AC—Why It’s Important and Why It Needs Professionals


If you’re considering getting a new air conditioning system before the summer, you’ll have to make several decisions about what type of AC installation to get. 

One of the critical factors to get right when installing a new air conditioner is ensuring that it’s correctly sized. This is another way of saying you need to find an air conditioner with the right level of cooling power for your home. Correct sizing is necessary for an AC to work effectively and energy efficiently—and this requires experts, as we’ll explain below.

What “Size” Means for an AC

No, it doesn’t mean the actual physical size of the air conditioner. The size we’re concerned with here is the cooling capacity of the unit, how much heat it can transport out of the house to cool it down. 

The cooling capacity of central air conditioners is measured in units called tons. One ton of cooling capacity is equal to 12,000 BTUs of heat removed per hour. Residential central air conditioning systems average from 1 to 5 tons. You want to find the tons of cooling necessary to keep your house at a comfortable temperature during the heat. 

Too Small, Too Big

It’s important for sizing to be exact. You don’t want to guess at this, since that makes it likely you’ll end up with a unit that’s too small or too big for your home.

Undersized AC

An AC that doesn’t have enough cooling capacity for a house will not be able to reach the target temperature on the thermostat. The air conditioner will instead run continuously as it attempts to achieve an impossible indoor temperature. This means extremely high bills and a house that isn’t comfortable. 

Oversized AC

It might sound as if it’s better to err on the side of an AC that’s too powerful. However, an oversized air conditioner is as big a problem as an undersized one. An oversized AC will lower the indoor temperature so rapidly that the HVAC system will register it has already completed its job and shut the compressor off early, then turn it back on a short time later and repeat the process. This rapid starting-and-stopping is called short-cycling, and it causes immense energy waste and extra strain on the system that can lead to an early replacement. It also prevents the AC from running long enough to evenly cool off the whole house.

Professional Sizing

So how do you accurately size your new AC? Simple: you rely on professionals. Licensed HVAC technicians will conduct a load calculation on your home that takes into account various factors (size, number of rooms, number of residents, insulation, heat gain from lights and appliances, radiant heat from windows, etc.) to determine the right size of AC to keep it cool without energy waste. We don’t recommend trying to do this calculation on your own: getting this right is essential, and you can trust our experts to ensure you have the ideal new cooling system for your family’s comfort.

Contact the Mechanical Air Conditioning team to schedule an appointment for your central heating and air conditioning needs. Serving all of Palm Beach County and the Treasure Coast. 

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