A common question we receive from customers is about run time of their current air conditioning system. Many question what is viewed as excessive run time. Actually, a properly sized air conditioner should run non stop while maintaining around 75 degrees inside when it is 95 degrees outside.
When we size air conditioners, we size for a 20-degree temperature spread between inside and outside. This means when it is really hot outside, your properly sized unit will run almost non-stop without changing the indoor air temperature much. This is important and is required to keep humidity levels as low as possible in your home.
When we are cooling, what really makes us comfortable is lowering of the humidity, not just making you home cooler. Lower humidity helps us to evaporate perspiration from our bodies. When an air conditioner is running, not only is it cooling the air, but the a/coil in the plenum is sweating like a cold glass of water. This is how we remove the humidity from the air. The water is collected in a drain pan and discharged to a floor drain. Most home air conditioners are removing about one gallon of water from the air per hour of run time.
So, if you have say and air conditioner that is twice as big as it should be, the run time would be half. Rather than removing that gallon of water from the air every hour, it is now only ½ gallon. The temperature will drop fast but the humidity will still be high. This will make the inside of your home feel like a cave. Cool but damp. Not the most comfortable situation.
Don’t worry about a properly sized unit running and using excess electricity either. An air conditioner that is sized properly will use way less energy that one that is oversized as any machine is most efficient when it is up and running, not cycling on and off. Compare it to city verses highway driving in your car.
Todays two-stage air conditioners actually take humidity control to an even higher level as they change their capacity based on how hot it is outside. Two stage units run slower, longer cycles when the weather is not severe and do a much better job with humidity control than a properly sized single stage air conditioning system.