During hot weather your air conditioner runs a cooling cycle that chills the evaporator coil using rapidly expanding refrigerant. Fans draw air over the coil and force the air through the ducts that lead to the rooms in your house to lower the overall temperature. This cooling cycle runs for a few minutes until the temperature is right; it then shuts down to save energy and prevent the air from getting too cold inside. How long the unit runs a cooling cycle varies based on several factors.
Based on Temperature
Your air conditioner's cooling cycle should last until it cools the house to your preference. There is no set time it should run. Instead, the cooling cycle is designed to create colder air in the house until the temperature on the thermostat is reached. It shuts off at that point and starts again when the house begins to warm up naturally. If it is just slightly warm outside, it probably won't run more than a few minutes. If it is blazing hot when your temperature is set fairly low, it may need to run much longer to reach the goal temperature.
How long your air conditioner cycle lasts may also be affected by the size of your system. The size of an air conditioner is measured in output BTUs. This indicates the amount of cooling it can produce in a given time. One BTU is equal to the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. If your air conditioner has more BTUs than it needs, it will run very short cycles more often. If it has too few BTUs, it will run much longer per cycle.
Assuming your installer recommended the perfectly sized central air unit for your home, it should be able to get both of its jobs done in seven-minute to 10-minute cycles. The air conditioner does more than blow cold air. It also removes moisture from the air to make the home more comfortable. If properly sized, the air conditioner will cool to the desired temperature and remove the proper amount of moisture within this time frame.
The Long and Short of It
If your air conditioner tends to run cycles much shorter than seven minutes or much longer than 10 minutes, there is a problem. Short cycling will overwork your air conditioner and use up unnecessary energy from starting and stopping cooling. It will also leave too much moisture in the air. Longer cycles have the obvious downfall in that they use excessive power to run the cycle for long periods of time.
Lee Morgan is a fiction writer and journalist. His writing has appeared for more than 15 years in many news publications including the "Tennesseean," the "Tampa Tribune," "West Hawaii Today," the "Honolulu Star Bulletin" and the "Dickson Herald," where he was sports editor. He holds a Bachelor of Science in mass communications from Middle Tennessee State University.