How to Tell if Your Furnace is Short-Cycling & What to Do

Winter is just around the corner. You can feel the cold breeze starting to kick in, and soon, the temperature will drop even more. This is the time of year where you need to make sure that you and your family remain warm and comfy despite the freezing weather outside. Now is the time to check your furnace, schedule a furnace tune-up, and inspect your unit to see if it is working as it should. After a period of inactivity, it may have some problems, some that can be repaired easily while others, not as much. One of such issues is furnace short cycling. This is when your furnace runs then shuts off and starts again repeatedly. This major problem needs to be checked by an HVAC professional as soon as possible.

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Is My Furnace Short Cycling?

A functional furnace will switch on and run until the set temperature is achieved. After that, it will switch off while the home maintains this temperature level. It will take some time until the furnace needs to switch on again, once the thermostat sensor detects that your home is cooling down. In contrast, a furnace that’s short-cycling will switch on and off repeatedly and it will do so in quick succession. The furnace will shut down before it can reach the desired temperature. This continuous turning on and off again will cause the system to wear out faster as well. You will also feel cold throughout the day even if the furnace is running.

Reasons Behind A Short-Cycling Furnace

homeowner feeling chilly due to short cycling furnace

A short cycling furnace should not be allowed to persist. It uses more energy than it should, causes damage to furnace parts, and makes your house feel uncomfortable. If you suspect that your furnace is short cycling, it is best to resolve it quickly. The correct remedy depends on what is causing the problem. Here is a list of the few things that cause furnace short cycling:

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Overheating Furnace

HVAC systems are equipped with features to protect them from damage. Your furnace is responsible for heating your home. However, your furnace can still get too hot. Fortunately, it can tell if the heat has reached a dangerous level. This will trigger the furnace to switch off immediately. This emergency measure helps prevent damage, like heat exchanger cracks, from happening. Toxic carbon monoxide can leak from these cracks, so it is better to stop them from developing in the first place. Overheating is typically caused by airflow restrictions due to clogged air filters and blocked exhaust vents.

Having A Furnace Bad Flame Sensor

gas furnace flame

A furnace with a bad flame sensor means that the flame will shut off immediately after it ignites. The sensor’s job is to monitor the gas valve. It acts as a safety precaution so that raw gas doesn’t get into your home. The sensor switches off when it doesn’t detect a flame. When you have a malfunctioning sensor, it will shut off the gas valve even when it is unnecessary. A dirty sensor can cause this, so cleaning it might fix the issue. Otherwise, the sensor needs to be replaced. Call an HVAC professional to help you do this.

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The Heat Vents Are Blocked

Furnaces heat air that is then pumped out the air vents. If this hot air can’t flow out of these grates, the heat is trapped inside and overheats the system. This will cause another short-cycling episode, which will persist unless the issue is fixed. Vents are equipped with dampers which are control mechanisms that allow the occupants to control if a room receives hot air or not. It is a helpful energy-saving feature. However, remember to keep at least 75% of all dampers open at all times. Otherwise, it can lead to overheating.

Furnace Filter Is Dirty

hvac air filter replacement

A dirty furnace filter can cause short cycling. When you have a malfunctioning flame sensor, it will immediately shut off your furnace. However, a dirty filter will let your heating system run for several minutes before shut-off. The heat grates might also be pumping out hotter air than average. A dirty filter can restrict air from flowing back into the furnace. Therefore, it cannot cool down and cause heat to build up to uncontrollable levels. As a safety measure, the furnace will shut down automatically. Clean washable filters or replace disposable ones when necessary.

Thermostat Is In The Wrong Spot In Your Home


Thermostats have sensors that measure the temperature inside your home. It then regulates the activity of your furnace per what is sensed in its surroundings. A thermostat that’s in the wrong spot might not work correctly. For example, it might be near a sunny window, lamp, or heating vent. These areas can skew with your thermostat’s sensor readings. It might think that the home’s ambient temperature is already hot, triggering the system to shut down prematurely. Make sure it is in a neutral location far from anything that can affect its temperature readings.

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The Exhaust Vent Is Blocked

It is recommended that exhaust vents are kept open at all times. Unfortunately, vents can get blocked by nearby shrubs, nests, beehives, and snow, among others. These blockages need to be removed as soon as you can. You should also check the vents regularly. This should be included as part of your system maintenance. In some cases, a dangerous animal might be what is blocking these vents. If this is the case, it is better to call animal control instead of exposing yourself to harm.

Furnace Is Too Large For Your Home

Buying a large furnace might seem like an attractive choice. After all, homeowners want to feel secure about their heating system’s capabilities. However, having a bigger heating system doesn’t mean that it is better for your home. A furnace that has excess capacity can result in furnace short cycling. Therefore, its parts will wear down faster, heating costs will be higher, and temperature swings will be more noticeable. The sensible but expensive solution is to replace it with a correctly sized furnace. Have a professional HVAC tech help you find the right one using precise calculations.

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Fix furnace problems early so that you have a comfortable home when winter arrives. If you are dealing with short-cycling, find the cause using the clues listed above. Consult with a professional HVAC contractor for proper inspection, diagnosis, and repairs. This way, you’ll enjoy a stress-free winter and have a heating system with a long service life.

Tevis Energy’s sister company, Modern Comfort, performs HVAC installations, replacements, tune-ups, and more. Our technicians can provide you with expert HVAC services to ensure that your system provides you with the comfort and efficiency you deserve. Call now to schedule an appointment.

Call Tevis Energy For All Of Your HVAC Requirements

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Tevis Energy offers superior HVAC services in central Maryland and southern Pennsylvania. Rest assured, we have the best professionally certified and highly trained technicians for all your excellent heating and cooling service needs, including maintenance, installations, repairs, and replacements. Each of our friendly techs has years of experience and extensive knowledge to service any HVAC system correctly.

Our company provides the most competitive HVAC service costs in the area. Our tune-ups can increase your energy efficiency and improve your comfort while also reducing your energy bills. When you need to repair or replace your HVAC system, we can recommend the most suitable solution for your home while staying within your budget. All of our work comes with a guarantee because your satisfaction is our priority. To book a service appointment, call Tevis Energy today. We offer free, in-home estimates.

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