A furnace short cycling is a common problem some Inland Empire area homeowners experience over the winter months. This furnace issue should not be ignored. A short cycling furnace results in poor comfort management, energy waste, and more wear and tear to heating systems. The heating and cooling experts at Sanborn’s are here to let you know what furnace short cycling is, how to spot it, and what to do about it.

What Is Furnace Short Cycling?

The amount of time a heating cycle runs varies based on your temperature settings and how much heat the furnace needs to produce for the home. Typically, one heating cycle is several minutes long. You may hear a slight click from your thermostat when it sends signals to your furnace to fire up and shut down, notice the slight sound of airflow as warm air begins to enter your living areas and stops, or if you happen to be near your heating equipment, it may be possible to hear the burners ignite or blower motor begins to run. This is all normal.

Furnace short cycling is just as the name sounds – it’s shorter heating cycles. The heating cycles don’t run nearly as long as they should, so your furnace starts up and shuts down after just a minute or two, or even a few seconds of operation. A good way to tell if your furnace is short-cycling is if your heater turns on and off several times repeatedly without producing any heat. 

A furnace that is the right size for the home and working properly cycles approximately three to eight times per hour. When temperatures outside are extremely cold, it is normal for some extra cycles to occur. When a furnace is short cycling, it’s working hard to produce heat but isn’t making any, causing strain on your furnace. If left unchecked, this could cause major issues for your furnace resulting in hefty repairs. 

What Causes Short Cycling in a Furnace?

There are multiple malfunctions that cause furnace short cycling. Some of these issues are easily corrected on your own, while others require the help of an HVAC professional. Our heating contractors in San Bernardino review the causes of furnace short cycling and what you need to do in each situation.

Dirty Air Filters

When you don’t change your dirty air filter on a regular basis, the filter media becomes clogged with contaminants which restrict airflow through the heating system. When the furnace doesn’t receive enough airflow, it overheats. Furnaces have a safety feature called a limit switch that causes an overheating furnace to shut down when internal temperatures become too high – a lack of airflow often puts temperatures up into this range.

So, the furnace is triggered to stop, then it cools down only to fire back up again. This short cycling continues to repeat until the furnace receives the airflow it needs.

Dirty air filters are one of the most common reasons behind furnace short cycling. As soon as you notice the signs of short cycling, check your filter – make sure it is not filled with contaminants and is installed snugly facing the proper direction. If you have a dirty or clogged air filter, change it right away and see if short cycling stops. You can buy most replacement filters at your local hardware store. To prevent short cycling from happening again, be sure to change your furnace filter every 90 days. 

Bad Thermostat Batteries

When thermostat batteries begin to go out, they often interfere with how the thermostat signals the furnace. A faulty thermostat may have trouble accurately reading the home’s temperatures, which also affects cycle length. Check to see if your thermostat has batteries and if so, replace them. Some thermostats are wired directly to the HVAC system. If your thermostat is over 10 years old, you may want to consider a replacement

Blower Problems

Problems with the blower are a less common cause of furnace short cycling, but still possible. The blower is responsible for circulating air through the furnace and into your home. If the blower stops working, your furnace still fires up, but without airflow created by the blower, high temperatures are quickly hit, and the limit switch shuts the cycle down.

When you notice short cycling from your furnace, go to your vents and feel for airflow. If there is no air or a weak stream of air coming out as the furnace runs, this points to blower problems – call your technician for furnace repair.

Improper Furnace Size

When furnaces are oversized for a home, furnace short cycling becomes a constant issue. A furnace that is too big rapidly heats the home, so the cycles are shorter. This may sound like a good thing, as your home is heated faster with less energy use – but it’s not. Those shorter cycles stress components at a faster rate, leading to breakdowns. Plus, heating with an oversized furnace leads to great energy waste. If this is the case, the only way to solve it is to replace your furnace with an appropriately sized unit.

Call Sanborn’s for Quick Furnace Repair

If you experience furnace short cycling this winter, call Sanborn’s Air Conditioning & Heating right away for quick and reliable furnace repairs. Our skilled HVAC technicians diagnose system issues and perform accurate repairs to stop short cycling and protect your heating system. Contact us today to schedule service.