East Coasters melted in the heat and high humidity last week. Some people are probably wondering if their air-conditioners are big enough.
All too commonly, we see comfort issues caused by air-conditioning systems that are TOO BIG. Too big? A lot of people are concerned about systems that are too small. And many contractors will size up “just in case” and to avoid call back complaints that the air-conditioner isn’t keeping the house cool. Sometimes they’ll replace existing systems with bigger systems. Generally that’s not the right answer.
An A/C that is too big pretty much ensures that you won’t be as comfortable as you should be most of the time. Systems that are too big can cool you house down quickly. But if you live in a humid climate, it’s more often the humidity that really makes us uncomfortable. To reduce the humidity, you need a smaller system that runs longer and pulls a lot more humidity from the air. The smaller system uses less energy per minute, so having it run longer doesn’t mean you’ll be using more electricity. Longer run times also mean that your system hit peak operating efficiency, something that it can’t do if it’s running only for very short periods of time.
There’s an additional problem caused by sticking a larger air-conditioner onto your existing duct system. Often the ductwork cannot handle the increased capacity and air-flow required. And again, this means your system won’t be operating efficiently.
If your system is older, you should consider replacing it with a system that is “right-sized” and more efficient. In terms of efficiency, look for Energy Star as a minimum—and a higher efficiency in warmer climates. And ask your contractor to size properly using “Manual J”—ask for the report. Multistage and variable speed equipment can help, too. If your current system doesn’t seem to be keeping you and your home cool enough, there may be other things that make a lot more sense than a bigger A/C. Good insulation, tight ductwork, and controlling heat gain are all important strategies to make you more comfortable and save money.