Furnace Short Cycles | What is Gas Furnace Short Cycling?
We recently had a question come in from our Furnace FAQ page, where the visitor wanted to know more about gas furnace short cycles, and what it meant to him with his brand new furnace in his home.
In this quick gas furnace article, we want to help you understand what gas furnace short cycle means, and why its bad for your home heating system. Most often on new systems, it’s due to not having the right size furnace in your home!
Furnace Short Cycles
Short Cycling is the process in which the following occurs:
- Thermostat calls for heat
- Gas furnace turns on and runs
- Within just a few minutes (usually less than 5 minutes) the furnace turns back off.
- Process repeats several times an hour.
This is commonly called a furnace short cycle.
Imagine if you will, sitting in your car on a cold morning. You get cold, so you reach up and turn the heater onto full-blast in your vehicle. Within 1-2 minutes, its more than you can take, so you reach back up again and turn it off. Now, repeat that process for the next 30 minutes on your way to work.
The reasons short cycling can be bad for you are many. Most importantly however are that short cycling prohibits the area from being properly heated, cost you more money to run your furnace and reduces the life of the unit!
My advice to you if the furnace is new:
- First, call out the company who installed it, explain the situation and ask them to provide your load calculation. Along with that, ask them to correct the issue.
- If they refuse, or cannot do so, call the Manufacturer Rep in your area, and ask for assistance.
Reasons for Short Cycling
While the reasons for your furnace short cycles can be endless, there a few that are most common, especially on a new unit installation. Assuming everything is working properly, check the following:
- Thermostat too close to the vents or heat source (Relocate the thermostat) and when the heat turns on, the thermostat is immediately warmed to the set point, and shuts back off.
- Gas furnace much too large for the area! Even a moderately oversize furnace is going to run OK 90% of the time. Oversize systems are not uncommon and can generally be adjusted down to eliminate short cycling. A grossly oversize system on the other hand is not going to do.
- Several closed vents, forcing too much hot air into a confined space. (Open other vents)
- Other, technical issues in limit switches, pressure switches etc. (You should call a technician)
Is Your Furnace Short Cycling?
Share the situation in the comment box below. Someone will surely jump in and help.