HVAC systems are designed to run for about 15 minutes per cycle, depending on the desired temperature and humidity levels in the space. However, sometimes units will “short cycle,” or run for a duration far less than the normal 15 minutes. This is typically not normal and can often be attributed to one of three main issues.
1. Oversized HVAC Unit – While a system too small is no good, a system too big also can lead to issues. When an air conditioner cools a room too quickly, it is unable to draw out as much humidity from a room, resulting in a less comfortable environment. To see if a system is properly sized, a heat/cool load calculation can be conducted.
2. Thermostat Location – Thermostats should be located on interior walls away from windows, air vents and direct sunlight to improve accuracy. The better a thermostat is able to sense the actual temperature of an area, the better the system will perform. Additionally, thermostats can be relocated as necessary.
3. Low Refrigerant Charge – Without the correct refrigerant charge, a system will not maintain proper pressure levels, which may activate the high-pressure control or low-pressure control switch. These are simply safety switches integrated in the HVAC system designed to protect the compressor from further wear and tear. Unfortunately, if a system is low on refrigerant, there is almost certainly a leak, which will require a repair of its own.
While short cycling may seem to be the least of your worries, it is actually an important issue that should be addressed. An inefficient unit will reduce system efficiency and energy savings. Furthermore, the overly frequent running of a system creates unnecessary wear on a system, leading to otherwise preventable issues down the road.