Gas Furnace Short Cycling [4 Easy Solutions]

Is your gas furnace short cycling and getting you concerned? Don’t worry because in this guid4e we have compiled a list of the possible causes of a short cycling furnace. And, because we hate to leave you without solutions, we have provided solutions for each of the reasons for furnace’s short cycles.

Before we dive into details let us first look at what is considered as the normal cycling period for a furnace.

How Often Should a Gas Furnace Cycle?

There are several variables that determine how often your furnace should cycle. But On average, the heating cycle should last from 10 to 15 minutes depending on factors such as the AFUE rating and the speed of the blower, characteristics of your house, the type of insulation, outdoor temperatures, and the age of your furnace.

The heating cycle time will also depend on the type of furnace you have. For example, average heating cycle will not be the same for furnaces with variable-speed blower fans and furnaces with single stage fans.

Possible Causes for Your Gas Furnace Short Cycling

1)Your Furnace is Overheating

 Gas furnaces come with built in safety system that shuts off the system when there is overheating. When your furnace is cycling too often, this could mean there is overheating within your heating system. There several causes for overheating, including restricted air flow into your furnace. There are several reasons why there is restricted airflow into and out of your furnace including the following:

Dirty or Clogged Air Filters:

• When was the last time you replaced your furnace air filters? If you replaced them more than 3 months ago, its high time you made another swap. Clogged air filters restrict air flow from coming through the heat exchanger. This can stop your furnace from blowing hot air.

• This causes the heat exchanger and other components of your gas furnace to overheat. And when there is overheating in your furnace, the built-in auto switch-off system kicks into action and shuts off your heating system to prevent damage to your furnace’s critical components.
  • Solution: Check your air filter to ensure that they are not dirty or clogged. And if they are, replace them. Filters can go for 3 months before they are replaced. But if you have pets or your environments has lots of dust, you can change them more frequently.  Clean air filters should stop the overheating in your system and the furnace should run properly without short cycling.

Blocked Exhaust Pipe.

• The venting exhaust pipe can become blocked with rats, bird ice or other objects and this can prevent the carbon monoxide from going outside. When the sensors detect that there is no exit for the burnt gases, the safety measure will flow into action and shut off your system. This can cause the short cycling that you are experiencing.
  • Solution: inspect the exhaust pipe for any objects that could have blocked it. If you cannot unblock it is a good idea to call in an HVAC professional

Dirt and Contaminants In Your Furnace

• They can affect how your blower fan works.  When too much dirt accumulates, the blower will struggle to blow away the air from the furnace for distribution into your home. This causes the internal components to overheat and shut off the system.
  • Solution: Regular and proper maintenance will keep your blower clean and debris free. If has dirt has accumulated on it, try cleaning it. If you are unsure of what do to with it, call for professional help.

Blocked Registers or Vents.

• Make sure the vents and registers in your home are not blocked for proper ventilation. Blocked vents and registers cause similar problems caused by clogged air filters.  If you have vents and registers that are blocked, air will not be able to get into the furnace for heating and so the furnace will overheat. Make sure the vents/ registers are not blocked by objects such as curtains, chairs, tables, or rugs
  • Solution: Sometimes registers and vents can be close accidently, if they are closed, open them. Remove objects near the vents such as the curtains, chairs, tables, and rugs.

2)Dirty Flame Sensors

• Flame sensors guard against leaking of the gases. They achieve this by closing the gas valve if they can’t detect the flames or natural gas in your furnace. Flame sensors can stay for a long time without the need to clean them. But as your furnace ages, dirt and dust can accumulate on the flame sensors and this could affect how they work.
  • Solution: The easiest way to fix a gas furnace that is short cycling is to remove the flame sensors, have it cleaned and put it back in your furnace. If the flame sensor issue is not fixed after removing and cleaning it, you may need to replace the flame sensor to get back your furnace to work.

3)Gas Furnace is Short Cycling: Oversized Furnace

• When your gas furnace is too big for your home it will be cycling frequently. This is because the furnace will be producing too much heat for your home quickly and be performing short heating cycles of 5 minutes or less. Quick heating cycles will affect the even distribution of heat in your home. It will create cold spots in rooms or spaces coupled with ridiculously high bills.
  • Solution: Call for professional service to come and find out if the furnace you are using is oversized or not. But always remember, before buying a new furnace get advice from experts one what size fits your home.

4)Location of Your Thermostat

• Make sure your thermostat is placed away from the furnace or any other heat generating appliances such as stove. If it is placed near heat generating appliances, it will always send signals to the thermostat to shut down before the heating cycle completes. Eventually your home won’t be Heat up enough due to the frequent short cycles. Another location to avoid placing your thermostat is near the windows. Sunlight can affect the operation of your thermostat.
  • Solution: Fixing this problem is easy. Remove your thermostat from locations such as window, air vents and other heat generating appliances. There shouldn’t be any short cycling problem with your furnace when the thermostat is sending it the correct signals.

Final Thought

A gas furnace short cycling could mean issues with your gas furnace. We have highlighted the common causes for short cycling furnace.  We hope that our solutions provided will get your furnace back to normal running. While some of these issues can be fixed as easily  as changing the furnace air filters, others need a professional hand.

Tim David

HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.