Why does my furnace turn on and off repeatedly? (short cycling)
There are several reasons why a furnace may turn on and off repeatedly, a situation called “short cycling”. The longer a furnace runs, the more efficient it operates, using the least amount of gas and electricity. When it short cycles, not only do utility bills rise, but so does the possibility of mechanical breakdown. More importantly, however, is the significant reduction in the life of the furnace. As you can see, short cycling is an expensive problem.
Every furnace has a control system and a safety system.
The furnace safety system is designed to stop the operation of the furnace when it operates beyond specific safety limits. In most furnaces, many safety system components will automatically reset when the unsafe situation is relieved. The reset allows the furnace to operate again until the safety limits are exceeded, at which point it stops the furnace. If the problem that caused the safety system to turn the furnace off isn’t repaired, the furnace will continue to short cycle. Other safety system components must be manually reset by a technician after the cause for failure has been corrected. If a manual reset safety has failed, your furnace may not operate at all, or the blower motor may run continually, blowing cold air throughout the home.
Sometimes, short cycling isn’t easily identified because the blower fan may continue to run, but the heat works intermitently. The safety system may simply close the gas valve so that the furnace will stop heating. Once the furnace cools, the furnace ignites and begins to heat again, all while the blower fan continues to run. If the air temperature blowing from the registers is inconsistent, the unit is likely short cycling.
Annual furnace maintenance will identify short cycling issues and provide money saving solutions.
Every furnace has a control system and a safety system.
The furnace safety system is designed to stop the operation of the furnace when it operates beyond specific safety limits. In most furnaces, many safety system components will automatically reset when the unsafe situation is relieved. The reset allows the furnace to operate again until the safety limits are exceeded, at which point it stops the furnace. If the problem that caused the safety system to turn the furnace off isn’t repaired, the furnace will continue to short cycle. Other safety system components must be manually reset by a technician after the cause for failure has been corrected. If a manual reset safety has failed, your furnace may not operate at all, or the blower motor may run continually, blowing cold air throughout the home.
Sometimes, short cycling isn’t easily identified because the blower fan may continue to run, but the heat works intermitently. The safety system may simply close the gas valve so that the furnace will stop heating. Once the furnace cools, the furnace ignites and begins to heat again, all while the blower fan continues to run. If the air temperature blowing from the registers is inconsistent, the unit is likely short cycling.
Annual furnace maintenance will identify short cycling issues and provide money saving solutions.
