What Causes a Furnace to Short Cycle

furnace inspection

Winter is steadily approaching and that means you have no time for a furnace that short cycles. You depend on your furnace to keep your home and family warm. Troubleshooting this problem can be fairly easy and you can also prevent your unit from short cycling in the future.

What does short cycle mean?
The term “short cycle” refers to the unit turning on and off quickly. When your furnace is working properly, the unit will come on and heat your home until the desired temperature is reached and then turn off. You’ll notice a major difference when your unit short cycles, as it’ll only come on for a moment and then stop very abruptly, your home also won’t be able to reach the temperature you’ve set on the thermostat.

Air Filter
During the months when your furnace is constantly in operation, you should be changing the air filter every 30 days. A dirty air filter could potentially cause your furnace to short cycle. The clogged and dirty air filter won’t allow the warm air to pass through into your home. All that warm air has to go somewhere, so it backs up into the unit. Since all the warm air backs up into the unit, this informs the thermostat that the room is already at the desired temperature so it turns the unit off.

Thermostat
If your thermostat is located in direct sunlight or located close to another heat source, it could be getting false readings. The heat source is heating just the thermostat so it’ll think that the room is warm enough and as a result, your furnace will short cycle. The thermostat could also be broken or not set to the correct settings, so before tearing your unit apart, inspect the thermostat to ensure it is working correctly.

Other issues
If the air filter and thermostat are not the root of the cause, there are several other possibilities that could be responsible for your unit short cycling. Your unit could possibly be either too big or too small for the space that it’s trying to heat. If you think your unit is not the proper size for your home, call an HVAC specialist for an expert opinion. There’s also a possibility that an object has fallen into the air vent, restricting the air flow. Whether it be a child’s toy or a part of the ventilation, you’ll want to call a professional for further inspection. A corroded flame sensor would also result in a furnace short cycling.

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Tom Gillece Sr. is the founder and president of Gillece Services in Pittsburgh, providing residential Plumbing, Heating, Cooling, Electrical and Waterproofing services throughout Western Pennsylvania. Established in 1980, Gillece has helped homeowners with all of their emergency, maintenance, repair and replacement needs for more than 30 years. For the latest news and offers, Gillece can be found on Facebook, Twitter, LinkedIn, and Google+.