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ServiceMax Blog

How Long Should My AC Stay Running?

spinning-fan-closeupOne of the most common reasons customers call our HVAC technicians for air conditioning repair in Chicago, IL is when they have an AC that’s turning on and off almost constantly over a short time. This is known as short-cycling, and there are many different potential causes:

  • A clogged air filter
  • Undercharge of refrigerant due to leaks
  • Leaks in the ventilation system
  • AC is too powerful for the space
  • Dirty or iced-up refrigerant coils

Short-cycling is both a symptom of a problem and a problem on its own since it significantly increases the workload on the air conditioner. Parts wear down faster, cooling bills rise, and the system will end up needing an early replacement.

But how long should an air conditioner’s cooling cycle last? Understanding this is important so you can know when you’ve got an AC that’s short-cycling.

The cycle-length depends on the heat and the thermostat

An air conditioning system uses a compressor to create the process of heat exchange. Only when the compressor turns on do the fans in the air handlers start to send around cooled air the rooms. When the compressor shuts off, the fans will circulate room temperature air. Whenever the thermostat in the house detects temperatures are hotter than the set temperature, the thermostat signals the compressor to turn on.

On an extremely hot day, the air conditioning system’s compressor may run continuously until the outdoor temperature cools down or an adjustment to the thermostat signals the compressor to cycle down. Essentially, as long as the house is still warm, the compressor will remain running to reach the temperature target. To avoid spending too much power to run the compressor, we recommend you place the thermostat to as high a setting as comfortable, such as 78°F.

(If the compressor is literally never turning off, no matter the setting or change in temperature, something is wrong. Turn off the AC at the circuit breaker and call for repairs.)

Too short a cycle

When the weather isn’t as hot, an air conditioner will usually run in cycles of around 15 minutes. This is enough to lower the indoor temperature to the thermostat setting whenever it gets too hot indoors. When the temperature cools down enough, the compressor will simply not activate.

But if the compressor is running for less than ten minutes at a time, then it’s landed in the in-between zone of short-cycling. Not only will this put too much strain on the air conditioner, but it will also waste immense amounts of electricity since the start-up phase of a cooling cycle is when the system puts the most demand on power. Call for a technician to find out which of the problems listed above is the source of the short-cycling.

The long and the short of it

To sum up: On extremely hot days, the air conditioning should run for long stretches. On warm days, it should run for 15 minutes at the shortest. If runs for briefer cycles than this, the system is short-cycling and needs help.

ServiceMax is open 24/7—All Day, Every Day! Schedule air conditioning repair whenever you need it.

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