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Why Does My Furnace Keep Shutting Off Early?

furnace-testingAs the temperatures drop at the start of the winter, you’ll have your home’s furnace running more often. Your furnace, however, may have other plans: it may start shutting downs far earlier than you expected. It may run for only ten minutes, or it may have the burner flames come on for only 30 seconds before going out again. No matter the situation, you’ll need it fixed for your home to enjoy comfort. 

Below we’ll look at potential causes of this problem to help you know when to call us for furnace repair in Cherry Hill, NJ.

A faulty flame sensor

If your furnace’s burners come on for only a short time and then go out again, the problem may be with a faulty flame sensor. The flame sensor is a safety device installed in the furnace designed to detect if the combustion gas coming from the burners has ignited. The sensor will shut off the flow of gas to the burners if there’s no flame to stop unburned gas from flooding the combustion chamber. If the flame sensor malfunctions, it won’t detect the flames and then turn the gas and burners off. Technicians can clean the flame sensor or replace it to correct this problem. 

The furnace is overheating because of poor airflow

This is another safety feature at work. The furnace has a limit switch that will shut the system down if the heat exchanger (the metal container where the hot combustion gas gathers) becomes too hot. This can occur if there isn’t enough airflow moving into the furnace and around the heat exchanger to cool it down. There are several potential sources for poor airflow:

  • The furnace filter is clogged up and needs to be replaced. We recommend replacing the filter every 1 to 3 months to prevent this. 
  • The blower fan is malfunctioning, possibly because of a lack of lubrication or too much dust and dirt on it.
  • Room vents around the house are blocked, placing a restriction on airflow.

If opening room vents and replacing the filter doesn’t solve the problem, you’ll need technicians to find out the cause of the low airflow. 

Malfunctioning thermostat

The problem might lie outside of the furnace itself and in the thermostat. If the thermostat is miscalibrated, it may sense incorrect indoor temperatures and signal the furnace to shut down too early. The furnace may also have faulty connections. Repair technicians can recalibrate the thermostat or whatever else is necessary to fix this. 

An oversized furnace

Is this a new furnace working its first winter for your home? Then it’s possible the furnace is too large (i.e. overpowered) for your house. A furnace that’s oversized will rapidly raise the temperature in the house, which may sound like a benefit, but it’s not. It will cause the furnace to shut down early, turn back on again, then shut down, over and over. You’ll probably need the furnace replaced—and make sure you work with our experienced professionals because we’ll see that you have the right-sized furnace. 

Make the Wise Choice, choose the home of the lifetime repair guarantee—Gibson Heating & Cooling!

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