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Here’s Why Your Oversized AC Unit Is Less Effective: Part 1

Here’s Why Your Oversized AC Unit Is Less Effective: Part 1


Air conditioner units. The bigger, the better … right?




As counterintuitive as it might sound, an oversized air conditioner unit is actually less effective. But what’s so bad about big a/c? Here’s the first reason why you need to avoid getting an oversized ac unit.


It’s All About Comfort


When your air conditioner is turned on, it’s doing 2 things.


First, it lowers the air temperature. And second, it takes moisture out of the air.


To take moisture from the air, the A/C needs to be turned on for an extended period of time. As the air is drawn over your air conditioner’s evaporator coil, it’s warm air passing over an extremely cold surface.


If everything works right, when the air passes over the coil, the air temperature loses 20° F. Because we live in a place with high relative humidity in the summer, the coil temperature must be below the air’s dew point.


Why? We need water vapor to condense on the coil.


Condensation requires time, and that’s where the air conditioner’s size comes in. An oversized air conditioner will only run for a short time because it cools your home very quickly. And then, it turns off.

When the a/c runs for a short of amount of time and everything gets really cold, but then returns to muggy shortly after it shuts off, this means your unit is too big.

That off-on-off action should be avoided. 


Water vapor will condense on your oversized AC unit coil. But it won’t be enough for the water to begin dripping into the catch pan beneath the coil. And for proper dehumidification, enough water must make it down into the pan for it drain to the outside of your unit.


That requires time. The air conditioner needs to run for a while to build up condensation.


Until the water actually drains to the outside, the air isn’t any less humid. The water on your coil is still able to evaporate – and make its way back into the air inside your home.


An air conditioner that’s sized right will run for a longer period of time before shutting off. If you want your a/c to reduce the humidity in your air as it cools it, make sure your cooling contractor doesn’t oversize it.




To make sure you get the right size air conditioning unit for your home, just call Dale’s Heating, Cooling & Plumbing. Our experienced comfort consultant will know just what you need.


This summer, beat the humidity in the comfort of your own home – with an a/c system that’s just right.