Why Does My Furnace Keep Turning On and Off?

Most homeowners adopt an “out of sight, out of mind” approach with their heating and cooling equipment, and rightly so. Aside from scheduling annual maintenance, and regular changing of the air filter, there’s not much else to be done—or is there?

While it takes a great degree of skill and training to become a qualified HVAC technician, as a homeowner, you’re more than qualified to determine when something’s not working the way it should, whether you come to that conclusion as a result of a decrease in comfort, unusually high fuel costs, or in the case of your furnace, frequent on and off cycling. While the cause of short cycling may be something minor, and easy enough to tackle on your own, it also may be a sign of a bigger issue, requiring the services of a professional. Read on for a list of possible reasons your furnace may be acting strangely, and some great advice on what to do about it.

Diagnosing Your Furnace Problems

Your thermostat is a master at regulating the temperature in your home, sending signals back and forth between your heating or cooling equipment, depending on the time of year. When you set the desired temperature, the thermostat senses the current room temperature, and calls upon the furnace once it dips below the set point. During normal operation, your furnace cycles off and on between three, and six times per hour. More frequent, brief periods of off and on activity, is known as short cycling, and should it continue undetected for a significant period of time, can cause irreversible damage to your furnace components, and an unwelcome rise in energy costs. Without scheduling an appointment for furnace repair with an HVAC specialist, you run the risk of your furnace dying on the coldest day of the year.

Why Is My Furnace Short Cycling?

Restricted Air Flow

If the airflow through your HVAC system is hampered, due to blocked supply or return vents, or most commonly, because of a dirty air filter, the heated air from your furnace will have nowhere to go. As it accumulates within your air ducts and back towards the furnace, your heating system receives a message that sufficient hot air has been deployed, and shuts off. Minutes later, the thermostat calls for more heat, the furnace starts up again, and the cycle continues. The solution? Change your air filter regularly, and ensure there are no objects blocking return or supply vents.

Malfunctioning Thermostat

While it may seem obvious, make sure your thermostat is set to “heat” before calling for service. Next, try changing the battery, and finally, ensure the unit is shielded from direct sunlight, drafts, or an alternate heat source such as a lamp.

Deteriorating Flame Sensor

This built-in safety feature can rust over time, and may require periodic cleaning, which is best left to a professional.

Improperly Sized Furnace

A furnace that is too large for your home may heat it quickly, but your interior will cool down just as fast, causing a series of continual on and off cycling. In addition to wasting energy, this repeated action will shorten the lifespan of your equipment, and result in more frequent repairs.

Furnace Repairs in Northern Virginia

At John Nugent and Sons, we want to help you and your family to stay warm and toasty this winter without having to spend any more than you have to on heating your home. We’re heating experts and have been helping Northern Virginia area homeowners like you for more than 40 years. If you’re experiencing any type of heating problem, our team is more than happy to help.

For furnace repair in Northern Virginia, schedule an appointment or call us at 703-291-1926.