Is It Considered Normal for an Air Conditioner To Run Every 10 Minutes?
Are you experiencing issues with your air conditioning constantly turning on, off, and on again? It’s normal for a central AC system to cycle on and off a few times an hour. On much hotter days or if your home is poorly insulated, you may also find that your AC system never stays off for all that long. However, there are also times when an AC that never runs for very long or cycles on and off constantly can indicate it has some type of issue. In this article, we’ll explain how long and often your AC should normally run so you can more easily determine if it isn’t working correctly or has any issues.
Typical AC Cooling Cycles
How often your air conditioning will run and how long it will stay off depends on the outdoor temperature, as this will impact how quickly your home starts heating back up after the AC shuts off. Thermostats are typically calibrated to signal the AC to start running when the temperature rises from 1 to 3 degrees above whatever the thermostat is set to.
A cooling cycle is when the air conditioning turns on until it cools the home down to the temperature set on the thermostat. An AC that works will typically perform two or three cycles an hour. On moderately hot days, your AC should typically only run for 10-15 minutes to cool your house thoroughly. This means it will often run for around 10 minutes before shutting off and then stay off for about 10 minutes. It will then repeat this same cycle twice more every hour. However, if your home is well insulated and has few places where hot air can leak, your AC may stay off for 30 minutes or so since your home won’t heat up as quickly.
Understanding Short Cycling and Why It’s Such an Issue
An air conditioning system that often only stays shut off for 10 minutes usually isn’t something you have to worry about. You do have to worry if your AC regularly shuts off in under 10 minutes, as this indicates it is short cycling. Another sign that your AC is short-cycling is if it frequently shuts off before the thermostat registers the correct temperature. If your air conditioner is turning on and off quickly, it may be short cycling.
Short cycling is a serious problem that will almost always lead to the AC condenser outside your house wearing out more quickly if you don’t repair the underlying problem. The compressor motor is always under lots of strain as it starts up. When an AC condenser constantly starts and shuts off, it puts additional wear on the compressor motor. It can significantly shorten the motor’s lifespan.
The compressor motor can’t be repaired and will always have to be replaced if it wears out. The problem is that replacing the motor costs about the same as installing a new AC unit. It generally never makes sense unless the compressor motor is still under warranty. Even then, the warranty won’t cover the cost of a replacement compressor if it wears out due to short cycling or a lack of maintenance.
Short cycling will also cause your energy bills to increase. The start-up current, or how much electricity the AC draws when powering up, is typically three to five times higher than the running current. This means that the more often your AC turns on and off, the more energy it will consume and the higher your cooling bills will be.
What Causes AC Short Cycling?
Central air conditioning systems can short cycle for a variety of different reasons. One of the more common reasons it will start happening is if the refrigerant level is low due to a leak. The refrigerant runs through an AC system in a closed loop. This means the only way the refrigerant level can decrease is if there is a leak in one of the lines or the evaporator or condenser coil.
Low refrigerant is a fairly serious issue, as it will usually cause the evaporator coil to freeze. If the coil is frozen, the refrigerant won’t absorb heat as it flows through the system. When the system works properly, the refrigerant absorbs enough heat that it changes from a liquid into a gas as it exits the evaporator coil and flows back outside. If the refrigerant remains in liquid form, it can cause the compressor motor to burn out. If liquid refrigerant enters the compressor, it can cause the oil in the motor to start burning. As a result, the motor will no longer be adequately lubricated and may quickly seize up.
All ACs have a low-pressure control switch that helps prevent this issue. If the refrigerant pressure drops below a certain point due to a leak or because the evaporator coil is frozen, the switch will immediately trigger the system to shut off to prevent it from being damaged. If the refrigerant level is too low, the switch will keep causing the system to shut off early and lead to its short cycling. The control switch can also malfunction and fail to correctly measure the pressure, leading to the system short-cycling and shutting off prematurely.
A miscalibrated, malfunctioning, or poorly placed thermostat can cause your AC to short cycle, as it may not correctly register the temperature. If your thermostat is too close to a supply vent, the cold air coming out of the vent will quickly make it think your home is cooler than it is. This will lead to the system frequently short-cycling and shutting off after only a few minutes.
If your AC condenser is oversized, it will almost always have issues with its constant short cycling. This is because it will work too effectively and cool too quickly, so it never runs for more than a few minutes. An oversized unit will also lead to the system freezing up more often and shutting down when the refrigerant pressure drops. Unfortunately, you can do nothing to overcome issues with an oversized AC other than replace it with a correctly sized unit.
Your AC can also start short cycling if the compressor keeps overheating. This can happen if the compressor motor starts to wear out, as it will then have to work harder and may quickly overheat. A dirty condenser coil can also cause the unit to overheat since this will prevent it from effectively releasing the heat it removed from your home. This last issue is easy to avoid by having the unit professionally serviced yearly. Annual maintenance and inspections often prevent most problems that can lead to short cycling.
If you’re experiencing issues with your AC short cycling, you can count on the expert technicians at Hoff Heating & AC for help. We service all makes and models of AC units, and we can resolve any issue. We can also assist with your AC maintenance and installation needs or if you need any heating service in O’Fallon or the St. Louis area. Call us today if you need an AC inspection or any HVAC service.