Three Reasons Why Your HVAC System May Be Short Cycling

If you are like most homeowners and are just turning your HVAC system to cooling for the season, you may not have had time enough to pay attention to how it is running. But if you notice that you system is turning itself on and off every few minutes, even if your system is cooling, you have a problem. Your system is short cycling and not only will this impact how well your system will work, but it could also possibly impact how long your system will last. Unfortunately, there are numerous reasons why this can happen, and you may need to eliminate each of these one at a time. 

You May Need A New Thermostat

One of the cheapest things that can cause your system to short cycle is your thermostat. This is one of the main features that determines how often your HVAC system turns itself on and off or cycles per hour (CPH). In addition to how your thermostat is set, CPH depends on many other variables. These include the following:

  • Outside temperature
  • Humidity
  • Infiltration rate
  • Size of your system and more

Most modern thermostats have a certain number of CPHs built in; these vary based on manufacturers, as well as on the size of the system. These can also sometimes be adjusted based on how long you want your cooling cycles to last. Your thermostat may allow you to choose 2, 3, 4, 5 or 6 CPH. A cycle is made up of both an on as well as an off period. 

For example: If you choose to have 3 CPH, your system will cool for 10 minutes, turn itself off for 10 minutes, cool 10 more minutes if needed, be off for 10 more minutes, and then do this one more time within the hour. Of course, it will also turn itself off once the temperature in your home reaches your desired level, and it may not come back on at the designated time if the temperature in your home has not changed. 

If you feel like your system is turning itself on and off a little too frequently, check your thermostat to see what your CPH setting is. Change this setting to see if this will have any impact on how often your system is cycling. If changing your thermostat setting does not have an impact on your system, there is a possibility that you have a bad sensor in your thermostat, or the information is not getting from your thermostat to your system. 

Your System Refrigerant May Need Charging

Low coolant levels in your system can possibly cause it to short cycle. Some systems even have a safety override that will not allow them to operate at all once the coolant level becomes too low. Normally, if your coolant levels are low, your system will not cool even during the brief periods that it cycles on. 

Unfortunately, if you have low levels, there is also a possibility that you have a leak somewhere in your system. For the best long term results, you will need your service technician to find and repair this leak, If not then you will find yourself having to call the service technician once your coolant leaks out again.

Your AC System May Be Too Big Or Trying To Work Too Hard

If you are in a new home, or you have performed renovations that have reduced the amount of space your unit is trying to cool, the unit you have may be too large and too strong for the size of the space that you are attempting to cool. This is often caused when you close off interior doors in an effort to reduce the amount of space that is being cooled. Closing off these doors, and reducing this space will often cause the space to cool too quickly. If your thermostat is located in the closed off space, once the desired temperature is reached, it will shut your system off. If you are going to keep this space closed off the majority of the time, you may want to consider moving your thermostat to a different location. 

These are just a few of the reasons that your system may be experiencing this problem. Your HVAC technician will be able to check these areas, as well as others. If you think your system is working harder than it should be then it probably is. Schedule an appointment with a plumber or HVAC technitian. to have it checked as soon as possible.