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How Often Should Furnaces Cycle?

Have you ever wondered, "How often should my furnace cycle?" There’s no set answer. On average, furnaces should kick on and off anywhere from 3-8 times per hour. However, if your furnace does so more frequently, don't assume it’s short cycling just yet.

Is cycling on and off normal?

How often your furnace runs per hour depends on several things:

  • Your home's insulation

  • Characteristics of the house

  • Outdoor air temperatures

However in some instances, frequent cycling may indicate an issue with the system. It may be because:

  • Wrong sized furnace: Short cycling is often the direct result of an oversized system. A larger furnace won’t heat a home faster nor will it evenly distribute air; the system will short cycle to keep temperatures equal throughout the house.

  • Overheating furnace: Overheating is a leading cause of short cycling. In many instances, restricted airflow is to blame. A blockage in the ducts or a clogged filter can stop air from flowing out of the system.

  • Your furnace is old: On average, furnaces last for about 15 to 20 years. As it reaches the end of its life, it may not run as efficiently as before. Short cycling is a common indicator that it is time for a replacement.

  • Malfunctioning Thermostat: The thermostat tells the furnace when to cycle. If it malfunctions or breaks, your furnace will not know when to stop running. Also, make sure the thermostat isn't too close to a heat source, it will not gauge the inside temperature accurately.

  • Dirty Flame Sensor: Does your furnace only cycle for a few seconds at a time? A dirty flame sensor may be the reason. Cleaning the sensor will help regulate cycles and prevent harmful gas leaks in your home.

If your furnace only turns on for a few minutes at a time, but your home never warms, call 72 Degrees Comfort Company at 515-965-7272 or email us at

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