When you have a furnace that turns on and then off abruptly or before it finishes it’s heating cycle, this is known as short cycling. Short cycling can lead to premature wear of the furnace. In addition, your home will never reach a comfortable temperature. Often short cycling can be due to a simple problem that can be easily corrected. Depending on the cause, short cycles may or may not require a visit from your HVAC technician. Hal Mechanical will share the different causes for a furnace to short cycle and what needs to be done to correct the problem.
Dirty Air Filters in House
It can be surprising for some homeowners to learn that a problem like short cycling can be caused by a simple issue such as a dirty air filter. However, it is also very true that a dirty air filter can cause more than short cycling. I can cause many other problems with both the furnace and air conditioning. When an air filter is dirty or the furnace’s direct filter is dirty, it causes stress on the furnace and the furnace will begin to overheat. The limit switch which is the furnace’s safety system will activate, which in turn will turn off the furnace. If the filters are never changed, the furnace will continue to overheat and the furnace will never be able to complete a single cycle. The answer is simple, change the air filter or the furnace’s filter when needed.
Sometimes a furnace will short cycle due to a problem with a thermostat. One common issue is as simple as a misplaced setting. Make sure the thermostat is on the “heat” setting and the thermostat is set to the right temperature setting. After checking these basic thermostat problems, another common problem is if the thermostat is installed too high on a wall. Heat rises fast and can cause the thermostat to trigger the furnace to turn off. Sometimes the thermostat is installed too high and it can cause short cycling, a thermostat should be 60 inches off the ground and no higher.
Furnace Flame Sensor Needs Replacement
Another cause for a furnace to short cycle is when the flame sensor is dirty. When the flame sensor is dirty it will cut off the gas supply and will not allow a flame to be produced. Because the flame isn’t there the furnace will not run and the system will shut off. An HVAC technician will need to come and inspect the furnace and the flame sensor. If the flame sensor is dirty it needs to be cleaned. In some cases, the flame sensor may even need to be replaced.
What Happens if a Furnace is Oversized?
There are those who think it is a good idea to install a furnace that is bigger than the one you may need. However, you should never install a furnace that is too big. One of the expected reactions of an oversized furnace is short cycling. Unfortunately, when you need to replace a furnace never install an oversized furnace. Short cycling is one of the many problems you get with an oversized furnace. If you made this mistake, you will need to replace the furnace with a proper sized furnace.