The Oversized Air Conditioner: Yes, You Can Have Too Much of a Good Thing

August 16, 2013
Ross and Witmer

The concept of bigger “is better” is a way of life, but it’s not the best in all areas. When to comes to your home’s HVAC system, an oversized air conditioner can cause any problems.

An oversized air conditioner is uncomfortable.

The operation of your A/C both cools and removes moisture from the air. To remove moisture, however, your system has to run for a while. As air passes over the evaporator coil and cools, the temperature drops below the dew point of the air and the resulting water vapor condenses on the coil. However the water has to do more than condense on the coil-it needs to drip into the pan and fill it enough for it to drain outside in order for this process to dehumidify the air. If this doesn’t happen, the water on the coil evaporates back into the indoor air. With an oversized air conditioner, the cooling load is quickly reached and the unit shuts down, preventing this process. If you don’t want your home to have rainforest-like humidity despite the temperature, don’t oversize it.

An oversized A/C has to be repaired more often and replaced sooner.
An oversized air conditioner starts up and shuts down a lot more because it doesn’t take very long to meet the thermostat setting. Every few minutes throughout the day as the temperature rises, it cycles on and off. A properly-sized unit would need to run longer-meaning less cycling-to maintain that same temperature. The more frequently your system kicks on and off, the more it wears, shortening its lifespan and resulting in potentially costly repairs.

Make sure your contractor properly sizes your A/C.
Don’t let a contractor estimate your cooling load based solely on the size of your home. Load calculations should include run-time, design conditions and more.

For more information about the challenges of an oversized air conditioner or any other home comfort needs, contact Ross & Witmer. Since 1945, we’ve made indoor environments more comfortable throughout Charlotte, Mecklenburg, Gaston, Union and surrounding areas.

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