Why is my furnace coming on when thermostat is off?

When a furnace keeps turning on and off, it is usually due to short cycling. This is the term used to describe problems originating from within the heating system. If short cycling is not promptly diagnosed and corrected, it could cause permanent damage to your heating unit and higher utility bills.

What would cause a furnace to keep running?





A dirty furnace filter is the number one reason we’ve found that furnaces run constantly. The air filter captures dust, pet hair, and debris that could damage the furnace and keeps it from getting to the heat exchanger. If the filter is dirty, it restricts airflow across the heat exchanger, which causes it to overheat!

Why would my furnace not shut off?

On your thermostat, look for the fan settings. There should be two, “ON” and “AUTO.” If it seems like your furnace won’t turn off, the thermostat may be set to “ON” for the blower. Toggle the switch to “AUTO” so your furnace’s blower fan only runs during a heat cycle.

Why does my furnace keep turning on and off?

So, if your furnace keeps turning off and on too quickly, your thermostat might be malfunctioning or broken. There are several things that could be causing your thermostat to not work properly. The wiring could be old and need replacing, it might need new batteries, or it could be the location of your thermostat.

Why does my furnace run every 10 minutes?

It cycles off because an inner safety is getting overheated from inadequate airflow. Either get a smaller furnace or enlarge the duct system to move the amount of air needed by the furnace.

Why does my furnace come on every 5 minutes?





Short cycle time: 2-5 minutes.

Your furnace has a part called a high-limit switch. If the furnace gets too hot, the switch shuts down the furnace. A dirty filter prevents a flow of fresh, cool air into the furnace to be heated and dispersed.

How many times should a furnace cycle in an hour?

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.

How do you know a thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken

  1. Thermostat Has No Power. …
  2. AC or Furnace Won’t Turn On. …
  3. Heater or AC Won’t Turn Off. …
  4. Thermostat Doesn’t Match Room Temperature. …
  5. Thermostat Doesn’t Respond. …
  6. Short Cycling. …
  7. Thermostat Forgets Programmed Settings.


How many hours should a furnace run in a day?

How Often & Long Should You Run a Furnace? Generally speaking, a healthy furnace runs for 15 minutes per cycle, two to three times per hour. The amount of these cycles will vary and depend on the time of year and how high you have set your thermostat.

Can a furnace run too much?

RUNS TOO MUCH & LOW HEAT – The gas furnace seems to run too long or the furnace kicks on too often. May be the result of a periodic safety shutdown that causes the furnace to stop burning during a heating cycle. This is often accompanied by a higher-than-normal gas bill and inadequate heating in extreme weather.

How long should a furnace run during a typical heating cycle?



10-15 minutes

With all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.

What temperature should you set your thermostat in the winter?

68 degrees Fahrenheit

The ideal thermostat temperature in the winter is 68 degrees Fahrenheit when you’re at home. Energy.gov suggests that 68 degrees is a good room temperature while you’re awake at home but recommends lowering it while you’re asleep or away.

Is 72 too high for thermostat in winter?



The lower the temperature is inside of the home, the slower the rate of thermal energy loss. To achieve optimal comfort, it is recommended for homeowners to set their thermostats between 68 to 72 degrees while there are people inside of the home.

Is 65 too cold for house in winter?

Even if you keep your temperature between 60°F and 65°F, your home or apartment may not be warm enough to keep you safe. This is a special problem if you live alone because there is no one else to feel the chilliness of the house or notice if you are having symptoms of hypothermia.