The Top 3 Reasons Why Your Furnace Is Turning On & Off Frequently

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Des Moines is known for its cold, harsh winters, which is why it is so important for your furnace to function properly. If your furnace is turning on and off frequently, it could damage the unit and cause you to pay higher energy bills. The frequency of the heater running may not necessarily be due to short cycling, which will be discussed later. It’s possible your furnace is turning on and off repeatedly because of other factors.

Keep in mind that the average furnace turns on and off 3 to 8 times an hour, so be sure to count the number of cycles and how long each cycle lasts before getting concerned that your furnace is turning on and off too frequently. You can find the most common reasons why your furnace is turning on and off below.

The Air Filter Is Clogged

This may be a recurring theme in our blog articles, but a clogged air filter is the number-one reason why your furnace may be turning on and off repeatedly. A dirty filter blocks the airflow, which causes the unit to overheat and automatically shut off as a safety precaution. Luckily for homeowners, a clogged air filter is the simplest and cheapest problem to tackle when it comes to maintaining your furnace. Turn the heater off, replace the dirty filter with a new one, and turn the furnace back on to see if it cycles normally. Changing the air filter will solve most of your furnace problems.

The Thermostat Is Faulty

The second most common reason why your furnace keeps turning on and off frequently is a faulty thermostat. If your thermostat is battery powered, replace the battery to see if that fixed the heater. If your thermostat is not battery powered, the panel will need to be opened to examine the low-voltage wires inside. Handy homeowners should be able to test their thermostats themselves; however, if you are not confident in your knowledge of thermostats and their wiring, call an HVAC professional to examine the thermostat for you. In some cases, the thermostat may just need to be relocated instead of replaced. Thermostats that are too close to a heat source, like a register or direct sunlight, think the house has reached its warm temperature and shut the furnace off too early.

The Furnace Is Improperly Sized

Unfortunately, an improperly sized furnace is the most expensive cause of frequent cycling since it will require replacing the unit. If the furnace is too big for your home, it will heat the house too quickly, causing it to shut off early. A furnace that is too large could also overheat. Likewise, a furnace that is too small could also turn on and off frequently. It’s best to call a heating and cooling technician to determine if your heater is the right size for your home.

What Is Short Cycling?

Frequent start-ups and shut-offs are often just a symptom of short cycling, which is why it’s common to believe your furnace is short cycling when the problem may really be any of the three causes mentioned above. A furnace that is actually short cycling will run for only one or two minutes before shutting off. Furnaces that operate the way they are supposed to will run for several minutes per cycle. That is why it is important to time your furnace cycle before it automatically turns off and count the number of times it cycles in one hour.

Whenever you have problems with your furnace, don’t hesitate to give Lenz Heating & Cooling a call. We’re here for all your furnace repairs or replacement needs and are proud to continue serving the Des Moines metro!