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Know the Limits of Your Home’s Air Conditioner

thermostat-and-woman-72-degreesSometimes an air conditioning system can seem like a magical device. For centuries, people knew how to create heat when they needed it, but they didn’t have methods that could cool the air aside from using water or opening up windows and doors. Then came the electro-mechanical air conditioner at the start of the twentieth century, and we had devices that could send cool air into a room—air cooler than that outside!—with just a few adjustments.

Of course there’s no “magic” to ACs aside from technology. And air conditioners do have limits. You can’t make your air conditioning system turn your house into a freezer, for example (not that you’d want to). A standard residential thermostat has the lowest setting of 60°F. So what are the limits of your home’s AC, and how can you best use this information?

The 20°F Temperature Differential

The limits of an air conditioner to lower the temperature is called its temperature differential. This is a measurement of the temperature of the air going into the air conditioner and the difference in the temperature that comes out. The general temperature differential for a central air conditioner in a home is 20°F lower than the current outdoor temperature. (In application, the differential can range from 16°F to 24°F when measured just against the indoor air, but 20°F is the standard.) 

The short version: your air conditioning system can make your home up to 20° cooler than the outdoor temperature. 

The Effect of the Temperature Differential

What happens if you set the thermostat to more than the AC’s 20° differential? Say it’s 90°F outside, and you put the thermostat at 68°F, which is more than two degrees lower than the AC’s maximum. The air conditioner will attempt to reach that setting on the thermostat and will continue to run until it registers that it’s reached it—which it won’t be able to do while the temperature outside is still 90°F. This makes the AC waste energy and put excessive strain on its components: an air conditioner is not supposed to keep running and running throughout the day, but periodically cycle-down. 

The good news is that the best setting for a thermostat during the day when people are home is 78°F, and that means the AC can handle most summer days. Once the temperature climbs over 98°F is when the cooling system will start to struggle to reach 78°F, and you may have to adjust the thermostat up higher to 80°F. If you know the limits of the AC, you can avoid making it waste too much power to run and putting it in jeopardy of a breakdown. 

For air conditioning in Plattsburgh, NY, the 78°F setting will work for most hot weather. This is the US Department of Energy’s recommended setting for daytime when people are in the house. If it seems a bit warm for your household, we advise you lower it to around 72°F and then raise it by one degree a day until people become acclimatized to it. 

Red Rock Mechanical, LLC serves Northwest Vermont and Northeast New York. Call us for 24-hour emergency service for your air conditioning.

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