Is Your Furnace Short-Cycling? Here’s What To Do

homeowner feeling chilly due to short cycling furnace

Winter is right around the corner. The temperatures are beginning to drop, and it’ll soon be uncomfortably cold even while you are inside your home. Keep your family from going through freezing nights by checking your furnace early. This way, you are sure that it is in perfect working condition. It might be having some issues, such as short cycling. This is when the furnace runs then shuts off and starts again in quick successions. If this is the case, contact a professional HVAC technician to inspect and repair any problems in your system.

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How Can I Tell If My Furnace Is Short Cycling?

A furnace that works properly will operate continuously until the set temperature is reached. After that, it will switch off and let the room maintain the temperature level. It typically takes a while until the temperature falls, and the furnace needs to turn on again. If your furnace is short cycling, the system will turn on and off again in fast and repeated succession. The thermostat setting won’t be achieved, and the constant switch on and off will only result in worn-out components. Not only that, but your house will still feel cold even with the furnace running all day.

Why Does A Furnace Short Cycle?

image of why furnace short cyclesWhen a furnace short cycles, it drastically reduces your system’s energy efficiency. It also causes wear and tear. If you suspect that your system is experiencing this problem, it is best to have it resolved right away. The solution will depend on the reason behind the short cycling.

In this article, we will delve into the different causes of this erratic behavior.

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HVAC equipment has built-in safety measures. This way, your system, and home are protected in case of accidents. When your furnace gets too hot, and the temperature has reached a dangerous number, your HVAC unit should turn off automatically. This emergency measure ensures that any damages are prevented. For instance, the heat exchanger could crack. If this happens, lethal carbon monoxide could leak and put your family at risk. Overheating typically occurs when airflow is blocked.

Bad Flame Sensor

gas furnace that isn't working properly

A faulty flame sensor will shut off the flame as soon as it is lighted. The sensor’s job is to keep track of the gas valve. It is a safety mechanism that ensures raw gas does not seep through your home by automatically shutting off the valve when there is no flame. However, a malfunctioning sensor will shut the valve off even if it is actually needed. An HVAC technician will need to clean or replace the problem to resolve this issue.

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Heat Grates Are Blocked

The heat grates are where heated air is pushed out into your home. If the air cannot flow as it should out of these grates, then the heat is trapped inside, and the system will eventually overheat and then short cycle.

Grates can be opened or closed using dampers. This is an energy-saving feature that allows homeowners to control which room gets heated. Keep in mind that at least 75 percent of these should be open at all times. Otherwise, overheating can occur.

Furnace Filter Is Dirty

image of a dirty furnace filter

The furnace filter is responsible for collecting dust, dirt, and other debris to have cleaner indoor air. However, the accumulation of these contaminants can block proper airflow. As a result, your furnace will run for a few minutes before turning off. The air that your furnace releases will also be noticeably hotter than usual. A dirty filter also results in overheating as the air cannot flow back to cool your furnace as it should. When the heat reaches unmanageable levels, the system will shut down automatically. Make sure to clean or replace the filter when necessary.

Exhaust Vent Is Blocked

The exhaust vent must remain open at all times. Unfortunately, there are times that the vents get blocked by various things, such as snow and shrubs. These should be removed immediately. The blockage can sometimes be tricky to remove, especially if nests, hives, or other dangerous animals block the vent. It is best to contact your local animal control to keep yourself from harm.

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Thermostat Is In The Wrong Spot In Your Home

hand increasing heating temperature at home

The thermostat is equipped with sensors to gauge the indoor temperature. This helps regulate your furnace so that it operates depending on the indoor environment. Your thermostat must be located in a neutral spot. There shouldn’t be any nearby heat sources as these could affect the sensor readings. The thermostat will think that the house is already too hot and will prompt the system to shut down.

Furnace Is Too Large For Your Home

Bigger does not always mean better. Although it might be tempting to purchase the biggest furnace for your home, it does not mean it would work best for your home. The excess capacity will only lead to short cycling. As a result, the components are more susceptible to wear and tear, and the temperature swings are more noticeable. Not only that, but there will be a drastic increase in your heating bills. Unfortunately, the only solution is an expensive one. You will need to replace it with a correctly-sized furnace. Contact your local HVAC technician so that they can conduct the proper calculations to find the right size, make, and model for your home.



A furnace that works as it should is necessary to keep your home warm and comfortable during the winter season. Determine the reason behind your short cycling furnace using the clues above. Get in touch with your local, trusted technician for proper diagnosis and fixes. This way, you can enjoy a stress-free and comfy winter.

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Miller Oil Company provides top-quality HVAC services in the greater Enfield, CT area. Our company hires only the best professionally certified technicians to conduct superior heating and cooling services, such as maintenance, repairs, installations, and replacements. Our techs are knowledgeable and experienced in providing accurate and quick HVAC services.

Miller Oil Company guarantees affordable heating and cooling services rates in the area. Our tune-ups can help increase your home comfort and energy efficiency while decreasing your home utility costs. We can also help you find the best HVAC replacement system for your home while staying within budget. All our works come with a guarantee. Book a service appointment with one of Miller Oil Company’s representatives today for a free, in-home estimate.
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