Short Cycling: Furnace Keeps Turning Off And On

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Short Cycling: Furnace Keeps Turning Off And On

When a furnace begins to start and stop frequently, this is called short cycling. 

Continuous short cycling could cause severe damage to the furnace, as well as increase your monthly energy bills.

Here are the top signs that your furnace may be short cycling.

Thermostat Is Malfunctioning

If your thermostat is malfunctioning, it will give incorrect readings to your furnace.

If your thermostat seems poorly calibrated or like it doesn’t respond to your commands, a technician may need to repair it.

When a thermostat sends incorrect signals to the furnace, the unit may turn on and off quickly, confused by its receiving signals. This is known as short cycling.


One reason that your heater must be turning down is because of the overheating of the heat exchanger.

The reason the furnace shuts down is to protect it from cracking as the exchanger overheats.

As the exchanger cools down, the furnace cycle turns on.

Area Around the Furnace

A furnace generates heat, so warmth around the unit is expected, but if it’s unusually hot near your furnace, the system may be overheating.

Overheating for any reason, like clogged filters or buildup inside the machine, can make a furnace short cycle.

Short Bursts of Air

You may not notice the furnace itself turning on and off repeatedly, but you may be able to tell if it’s releasing short bursts of warm air indoors.

Do your vents seem to expel short-lived gusts of warm air, shut off quickly, and repeat multiple times?

The furnace should release a steady stream of heat; otherwise, it may be short cycling.

Denver furnace service by First String Heating

If you have any questions about these furnace short cycling tips, or if you’d like a heating system serviced or installed in your home, contact us at First String Heating or call us at 303-250-4422.



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