When a furnace short cycles it will turn on to only shut off suddenly or before the inside of the home is properly heated. Short cycles can occur for a few different reasons. Some are easily corrected even without the aid of an HVAC technician. However, other short cycling problems can require deep diagnostics and repairs. Ambient Heating & Air Conditioning will share some of the causes for furnace short cycling and how they can be corrected.
Furnace is Overheating
One of the primary reasons why a furnace will end a cycle early or shut off suddenly is when it begins to overheat. If a furnace overheats, a number of components can be damaged and even lead to a fire. A furnace has an internal safety mechanism that is designed to detect overheating and turn off the furnace. Essentially, a short cycle is mainly due to overheating. However, what is causing the overheating needs to be determined. The source of reason for the overheating needs to be located and corrected to stop short cycling and prevent a potential disaster. Following are some of the reasons why a furnace will overheat.
Dirty Air Filter
A dirty air filter can lead to a furnace overheating. This is because the air flow becomes more and more restricted as the filter accumulates more dust. The air flow restriction causes the furnace to work harder. This leads to longer cycles which equals overheating. Make sure to change out the air filters to prevent overheating.
Closed or Blocked Air Vent
As the heated air is created, the blower will send it through the ductwork and into various areas of the home. If the air vent is blocked or closed the heated air hits a wall. As more and more is produced, the heat will push back and into the furnace. This will cause heat to build up. The limit switch will detect the heat and turn off the furnace. Make sure all of the air vents are fully open even in the areas you don’t need to be heated. Next, check all of the air vents that may be lower to the ground and make sure no furniture is blocking them.
Blocked Flue or Exhaust Vent
A furnace uses an exhaust vent or flue to release the harmful gas safely outside. The exhaust or flue can become blocked, and quite often by a bird nest. The exhaust or gas which is fairly warm, can get backed up inside the furnace, again causing overheating. The flue or exhaust vent will need to be cleaned to prevent the furnace from overheating.
A furnace that is too big for the actual heating space is never good. One of the expected side effects of an oversized furnace is overheating. Many homeowners will install a larger furnace in hopes to improve efficiency. However, this isn’t how furnaces work. They will overheat the home and themselves when they are too big. Never install an oversized furnace.