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Triple O Heating, Cooling, Electrical & Plumbing Blog

Why Does My Furnace Keep Shutting Off Early?

It’s a cold day outside, but you’ve got a powerful gas furnace to take care of keeping you and your family cozy. You hear the furnace kick on, warm air starts to come from the vents, and then … nothing. The furnace shuts down before it could get started making your home toasty and relaxing. Later, it turns on again, and this time … nope, it shuts off early again. Maybe it was one for several minutes, or maybe less than a minute.

What’s going on? Obviously it’s a problem, and you may need professional furnace services in Rochester, NY to solve it. Below we’ll take a look at reasons for a furnace that seemingly doesn’t want to do its whole job.

Thermostat malfunction 

One of the common reasons for a furnace that isn’t getting your home as warm as you want it is because it has an incorrect reading of how warm the house is in the first place. The thermostat, which senses the indoor temperature, may be miscalibrated so it’s registering the house as warmer than it actually is. This requires having professionals recalibrate the thermostat—don’t just raise the thermostat setting higher!

Clogged air filter

The air filter for your furnace will get dirty after one to three months and need to be replaced with a clean filter. If a dirty filter stays in place, it will cause a wide range of problems, among them, making the furnace overheat. A clogged filter will restrict the amount of air the blower fan can pull into the furnace and run across the heat exchanger. Without enough air, the heat exchanger will remain too hot, and a device called a limit switch will automatically shut off the furnace. Take out the filter and put in a clean one to see if this allows the furnace to complete a full cycle.

Faulty limit switch or flame sensor

We just mentioned the limit switch above, which is a key safety feature for a furnace. The flame sensor is another important safety feature that makes sure the gas from the burners has ignited so unburned gas doesn’t flood the combustion chamber. Both of these devices can fail so that they work too well, incorrectly sensing the furnace has a problem and shutting it off. You’ll need to have technicians repair these safety features to get the furnace working normally again.

The furnace is too large

If this is a new furnace in your home, then the problem might be that whoever installed it (probably an amateur) didn’t correctly size the system for the house and put in one that’s too powerful. An overpowered furnace will rapidly raise the temperature in the house so it will incorrectly sense it’s already finished its heating cycle and shut off early. The only solution to this problem is to replace the furnace with one that professionals have sized.

Don’t worry if you can’t figure out what’s wrong with your furnace. You can depend on our technicians to diagnose the issue and have it fixed right.

Triple O Heating, Cooling, Electrical & Plumbing Is Your One-stop Shop for HVAC, Plumbing and Electrical. Rely on us for all your home heating needs this winter.

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