One characteristic of an efficient air conditioner is its long, on-cycle operation. The air conditioning cycle time means the amount of time the air conditioner is running to cool your home to your desired temperature. Normal air conditioner cycle times are dependent on an HVAC unit of the correct size, but you also need a home with a sound and well designed airflow distribution system to meet your home cooling needs. The cycle time can also vary based on the weather, with the unit running for longer periods when it's very hot.
Normal air conditioner cycle times can vary depending on the size of the unit and the distribution system in your home. A minimum of 15-minute cycles is typically considered efficient and keeps humidity in your home under control.
Groundwork for Normal Cycle Times
Proper airflow distribution is an important part of keeping cycle times normal. The Air Conditioning Contractors of America (ACCA) has developed specific guidelines for proper airflow distribution design and correct AC equipment and size selection to reach cooling load requirements. Manual D of the ACCA, for example, sets proper air speed at the return grille of the AC system below 500 feet per minute and a maximum supply air speed at the register under 700 feet per minute. This should provide for long and efficient AC cycles and prevent humidity from creeping into your indoor air.
Normal Air Conditioner Cycle Times
If your HVAC system is properly sized with appropriate ductwork, air conditioning cycles should run at least 15 minutes at a time. The cycle will run two to three times per hour. In very hot conditions, the air conditioning can run nonstop for hours to try to lower the temperature to your thermostat settings. If your air conditioner cycles are under 10 minutes, it could indicate that the unit is too large or that there's a problem with the HVAC system.
A proper AC unit running under a normal cycle time in your home should help keep your energy bill low, keep indoor moisture out and create a comfortable and quiet flow of air throughout the house. Airflow inside your home should move at a relatively low speed, allowing the air filters in your AC system to do their job and prevent the system from placing undue stress on your AC unit. Furthermore, normal cycle times will keep AC system maintenance low.
Choosing the Right AC Unit
For an air conditioner unit to provide a correct cycle time, it has to match the cooling load needs of your home. When choosing the HVAC unit size, you need to take into account the normal temperature for your geographical area and the ideal indoor temperature as well. If you're replacing your AC, your HVAC technician will calculate the cooling needs of your home and recommend the appropriate AC unit size.
Normal Cycle Times Problems
Perhaps the most prevalent cycle time problem is due to an oversized AC unit, which causes shorter cycles. This is not the only one or the most damaging one, though. A larger than normal home with restrictions in the duct system and inadequate ceiling insulation leads to electric utility peaks and high-energy costs.
Another potential cause of short cycling is a clogged air filter. So proper inspection and an adequate maintenance schedule for your HVAC system will help you reach and maintain normal air conditioner cycle times.
- Carolina Comfort Heating and Air Conditioning: For What Length of Time Does an Air Conditioner Cycle?
- Conditioned Air Solutions: How Long Should My Air Conditioner Run in a Cycle?
- Touchstone Heating and Air Inc.: The AC Cooling Cycle: How Long Should It Last?
- Air Conditioning Contractors of America: Residential Duct Systems Manual D
Since 2003 Dan Ferrell has contributed general and consumer-oriented news to television and the Web. His work has appeared in Texas, New Mexico and Miami and on various websites. Ferrell is a certified automation and control technician from the Advanced Technology Center in El Paso, Texas.