Why Is My Furnace Short Cycling?

Does it seem like your furnace is running shorter cycles and struggling to keep up with the temperature you set in your home? If this sounds like a familiar scenario, your furnace is likely short cycling – and you need to act fast to prevent further damage.

In our most recent blog, the HVAC professionals at Schebler Heating and Air discuss what furnace short cycling is, what causes it and how to fix this issue. For all of your heating and cooling needs, contact Schebler today.

What Is Furnace Short Cycling?

Short cycling is just as its name suggests – your furnace runs shorter heating cycles than it’s supposed to. A normal heating cycle lasts about 10 to 15 minutes on average, and perhaps even more during extremely cold weather. A short-cycling furnace may only have cycles of a few minutes, or even a few seconds. This inhibits your furnace from properly heating your home to the set temperature.

Short cycling isn’t an issue that should be taken lightly. The frequent starts and stops cause excess wear and tear to the system and its parts, possibly even affecting the unit’s overall lifespan. Damage to heat exchangers, blower motor and other expensive components may result. Short cycling also wastes energy and can cause your energy bills to skyrocket.

What Causes Furnace Short Cycling?

There are several issues that can lead to furnace short cycling. Some can be taken care of DIY, while others require the assistance of a professional HVAC technician to make the appropriate furnace repair. Common causes of short cycling include:

Dirty or Clogged Air Filters

A dirty air filter or clogged air filter is one of the most common causes of furnace short cycling and one of the easiest to fix. A dirty air filter inhibits airflow into your furnace, which can cause your furnace to heat up to unsafe levels. When this occurs, the unit’s controls shut down the system for safety precautions.

If you notice your furnace is short cycling, the first thing you should do is check the filter. Replacing a clogged air filter is simple and immediately improves air flow into the furnace.

Improperly Sized Furnace

The size of a furnace doesn’t refer to its physical size; it is based on its capacity to heat a home. A system that is too large, heats the home too quickly, causing cycles to shut down after just a few minutes. This often leads to uneven heating and cold spots, especially in areas farther away from the furnace.

A furnace that turns on and off too frequently can increase energy bills, wear out parts quicker and decrease the system’s lifespan. Unfortunately, the only solution to an oversized furnace is to buy a furnace that is the correct size for your home.

Closed Vents

Closed supply vents around your home can also lead to a short cycle. When vents are closed, heated air cannot escape into your living areas. Instead, it backs up into the furnace and causes the unit to overheat, forcing it to shut off. To avoid this cause of short cycling, make sure all of the vents in your home are open and not covered by furniture. That blocked exhaust vent under your rug could lead higher utility bills or even a broken heat exchanger.

Faulty Flame Sensor

A furnace’s flame sensor is responsible for detecting a flame from the burners. If the flame sensor becomes faulty over time due to corrosion or rust, it can malfunction. If it is unable to detect a flame, the furnace will shut down for safety reasons. Have a professional HVAC technician inspect the flame sensor to see if it can be cleaned or whether a new flame sensor needs to be installed.

Thermostat Issues

The thermostat is the heart of your heating and cooling system, as it signals the system when to start and stop a cycle. An old or faulty thermostat may struggle to read the home’s desired temperatures accurately which can affect cycle times. If your thermostat is more than 10 years old, it might be worth looking into installing a new programmable or smart thermostat.

Contact Schebler for Heating Repair Services

If you notice signs of furnace short cycling, it’s important to contact a reputable HVAC company as soon as possible. At Schebler, our HVAC technicians are expertly trained to identify any issues with heating equipment and make the appropriate repairs or replacements. Contact Schebler Heating and Air today to schedule an appointment.