Have you ever looked at the thermostat in your home and thought about how cold you might be able to make the rooms if it could be set lower than the 60–63°F? That’s the usual limit on thermostats, and people rarely want the house any colder than that. They rarely want it colder than 68°F! But could the air conditioning system conceivably cool the house even lower? Or, to put it another way, just what is the cooling limit for your AC?
Answering these questions isn’t only an exercise in hypotheticals. You can learn important facts about how your AC runs and how best to manage thermostat settings when you know an air conditioner’s limits.
Capacity vs. Temperature Differential
What you need to know to understand the cooling limits of an air conditioner is the difference between an AC’s capacity and its temperature differential.
The capacity of an air conditioner is how much cooling it can put out—or literally how much heat it can pump out—from an indoor space in a given time. This varies significantly across different systems, and finding the right capacity is an essential part of selecting an AC for installation. An air conditioner must be correctly sized so its cooling capacity matches the house. Too little capacity and the AC won’t be able to meet standard comfort requirements and will continue to run and run. Too much capacity and the AC will short-cycle, turning off after a short time and then starting back up again because it’s too quickly lowering the temperature. AC capacity is measured in “tons” of cooling, which we discussed at length in a recent blog post. Most residential ACs have 5 to 10-ton capacity.
Temperature differential is the measurement of how much the AC can lower the temperature of the air that enters it through the return air ducts. This is different from capacity because it’s fixed—no matter the capacity of the air conditioner, the amount of space it cools to a comfortable temperature—the temperature differential is the same. An air conditioner can lower the temperature of incoming air by a maximum of 20°F. So no matter how low you set the thermostat, the air conditioner will only be able to drop the indoor temperature by 20°F. This is true even of an air conditioner that’s perfectly sized for a house. If the air going into the AC is 90°F, it can extract at most enough heat to get the air cooled to 70°F.
The good news is that this 20°F differential is more than enough to deal with the heat in a home on almost all days (provided the AC is the right capacity). The air inside a house is usually already cooler than the air outdoors because of insulation, and the recommended temperature for comfort is around 78°F. Even if you set the thermostat to 72°F, the AC can handle that as long as the air entering the return ducts is 92°F or lower.
We recommend not setting your thermostat lower than 68°F during the summer to ensure that you’ll keep the AC within its temperature differential. You shouldn’t have any trouble staying cool all summer long this way. If your AC does have trouble keeping up, you may need air conditioning repair in Conway, AR. Call us and we’ll take care of you.
Dewees HVAC proudly serves the Conway area. Call us for air conditioning service—we’re here to keep you comfortable!