Is My AC Unit Too Big or Too Small?

Summer is just around the corner, and for those who live in the Phoenix area, that can only mean one thing – seriously high temperatures. If you spent last summer thinking your home was a bit too hot, you could have a problem on your hands, and in some cases, it may mean that your current AC unit is not the right size. Upgrading to something bigger, though, isn’t always the best idea. Wondering why? Take a look.

Why Bigger Isn’t Always Better

Conventional wisdom would say that if you’re not cool enough in your home, you should just go with a bigger unit so you can get the most possible cooling power, right? Not exactly. When an air conditioner runs, there are two main goals it has to accomplish. First, it has to remove moisture from the air. Second, it has to actually cool the air. To get rid of that moisture, the unit actually runs for some time. The air itself passes over the evaporator coil, then it drops in temperature. A higher relative humidity means more condensation on the coil. It can’t actually drip to the pan until you have enough, and until all of that condensed water makes it outside, you’re not doing the de-humidification job. The bigger the unit, the less they run because of that equation, which means your home won’t actually be cooler and dehumidified.

While the humidity equation doesn’t always matter out here in Phoenix, what does certainly matter is the fact that starting up and shutting down wears out your HVAC system quickly. The more often it starts up and shuts down, the shorter the overall lifespan. Guess what? The bigger the unit, the more it starts up and shuts down because it only has to run a short amount of time to cool the house. So, it starts up, runs for a bit, then shuts down again. A few minutes later, it starts up, runs for a bit, then shuts down again. Over a given day, you’re going to see far more of this than you ever imagined with the wrong size AC unit.

What You Can Do

Looking to prevent this problem? Choose the right sized air conditioner from the start. Too big or too small and you’re going to have a problem on your hands. You need to know how many thousands of BTU/hour you’re getting. HVAC units are measured in tons. A one ton unit moves 12,000 BTU per hour. Home HVAC units range from one to five ton units. To decide how many tons yours should be, find out the home’s square footage. Multiply that by 25, then divide it by 12,000. Take that number and subtract .5. The resulting number should give you a range for your unit.

The right size means the perfect cooling capacity for your home, so do the math first and get an AC unit that’s just right.