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Why Is My Furnace Running Constantly?

Why is my furnace running constantly? Many people ask this question while wondering how long a furnace should run before shutting off. What if your furnace keeps running when the thermostat is off?

Gas furnaces that run constantly are annoying to listen to, wear down the system, and increase your monthly energy bill. Luckily, the possible causes are easy to spot and don’t take long to fix. 

Here at Air Specialties, we’ve provided a list of reasons to help you answer the question of why the furnace is running constantly. We’re your CT heating specialists, with a team of certified technicians that can diagnose and repair any problem with your HVAC system.

What Is the Typical Furnace Run Time?

How long should a furnace run before shutting off? Typically, you can expect furnace cycles to run two to three times per hour. Each cycle runs for about 10-15 minutes. During freezing weather, this cycle may increase slightly.

Reasons My Furnace Is Running Constantly

Why is my furnace running constantly? There are several reasons why this may be happening. Here are some steps to follow to troubleshoot the cause of the issue:

1. Dirty Furnace Air Filter

A dirty furnace filter is the most common reason why your furnace may constantly be running. Your HVAC system must pull air into the equipment to warm the air before it circulates back out through the vents. 

A dirty air filter can obstruct your furnace, causing it to work harder to meet your heating demands. However, it will continue to run until your home reaches the desired temperature. 

If your air filter is dirty, replace it with a new one. You should do this every 1-3 months.

2. Wrong Thermostat Setting

Why is my furnace running constantly? If your thermostat is set too high, it will keep running to get it to that temperature. You may notice your house is hot before becoming aware that the furnace keeps running. Check your thermostat to see the set temperature. 

It’s also possible that you have a malfunctioning thermostat. For example, if your thermostat runs after the temperature change, it may be faulty.

3. Blower Issues

When your furnace is turned on but not producing warm air, the cause is likely an issue with the blower. For example, the blower may have corroded wires, or the fuse may have blown. 

If your room temperature feels colder than usual, check your thermostat. Since this problem involves electrical components, contact a professional HVAC company to fix the issue. 

4. Faulty Limit Switch

The limit switch controls the heat in your furnace. When the thermostat sends a signal to the controller that it’s time to turn on the heat, the switch sends a signal to the furnace. 

If your furnace has a faulty limit switch, it may not receive the signal. This lapse can cause it to run more often than necessary. A faulty limit switch may also be why your furnace keeps running when the thermostat is off. You should call an HVAC technician to perform an inspection if you suspect this is the issue.

5. Malfunctioning Pilot Light

A pilot light ignites the gas before it reaches the burner. If it’s malfunctioning, the broken pilot light can cause your furnace to run constantly. The reason is that the system can’t reach the set temperature without a sufficient supply of gas to warm the air. 

If the pilot light is malfunctioning, you may need to call an HVAC professional to have it replaced. In addition, you can find the reset button on your furnace to try resetting the pilot light, which may solve the problem. If this doesn’t work, it may be an issue with the heat exchanger.

Schedule an Inspection or Repair With Our Service Experts

Why is my furnace running constantly? How long should a furnace run before shutting off? Does your furnace keep running when the thermostat is off? Air Specialties can inspect your furnace and repair any heating system problems. 

Air Specialties also provides furnace cleaning in CT to ensure your furnace runs efficiently for the winter. Contact us today!

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