In general, most furnaces run for approximately 10 to 15 minutes before cycling down. With an effective air delivery system and a well-insulated home, this should be long enough to establish your preferred temperature throughout the building.
Most furnaces kick on and off between three to eight times an hour, depending on things like outdoor air temperatures, the furnace's age, and how much insulation you have. That's why, instead of asking how often a furnace should cycle, it's best to stay alert to changes in how your furnace is running.
So, how long should a furnace run before shutting off? Most furnaces perform two to three heating cycles per hour. Each cycle lasts ten to 15 minutes and evenly distributes warmth throughout your home. However, longer or shorter heating cycles aren't always a cause for alarm.
This is commonly caused by a dirty air filter. Once high temperatures are reached within the equipment, the limit switch shuts down the heating cycle for safety reasons. Then the furnace must cool down before another cycle starts – but the issue just happens again.
Restricted airflow
Blocked vents or a clogged air filter may cause your furnace to run and then shut off too early. It's easy to fix these issues on your own.
Common issues include: Old wiring or dead batteries: Replace batteries or old wiring to ensure accurate temperature readings. Thermostat location: If your thermostat is too close to a heat source (like sunlight or a heat register), it can misread the temperature and cause your furnace to keep shutting off.
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.
When a furnace runs constantly, it probably means that something is dirty or clogged.
Having a dirty air filter in your furnace can cause short cycling. While a faulty flame sensor will lead to an immediate shut-off, a dirty filter will allow your furnace to run for several minutes and then shut down. You might notice that the air being pumped out of the heat grates is significantly hotter than normal.
One of the leading causes of short cycling is an oversized furnace. If your heating system is too powerful for your home's heating demands, it will quickly heat your living space, causing the thermostat to reach the set temperature and signal the furnace to turn off.
The Average Runtime for Furnaces
HVAC maintenance companies explain that a furnace will normally perform an average of two to three cycles in an hour, with each cycle lasting 10 to 15 minutes.
With all that being said, if there are no extreme factors involved, the average run time for a furnace is 10-15 minutes per cycle. Your furnace may need to run two to three times an hour to maintain your desired temperature if your home has average insulation.
If someone is at home in the daytime, 72° F (22° C) is a good start, but aim for 68° F (20° C). If everyone is away from home in the daytime or you're asleep at night, we feel 66° F (19° C) to 62° F (17° C) is best.
While it should cycle throughout the day, clicking on too frequently may indicate a problem. Homeowners often find themselves wondering, "How often should my furnace cycle?" The answer lies in a gray area. On average, furnaces should kick on and turn off anywhere from three to eight times per hour.
Rather than running constantly, your furnace operates in cycles allowing it to heat your home without constantly being “on.” Generally speaking, your furnace will only be actively producing heat for up to 9 hours a day over multiple cycles.
Routine Furnace Cycles and How Often the Heater Runs
Running 10 to 15 minutes per cycle seems acceptable. So is running as long as 20 minutes. Even running every seven or eight minutes may not be a problem, as other factors could lead to more frequent cycling.
There are multiple reasons why your furnace is short cycling. These could include a dirty filter, blocked vent, or malfunctioning flame sensor. You can switch for a clean furnace filter, or have your HVAC technician resolve a more complicated issue.
Leave the breaker(s) off for at least 10 minutes while the system is off and “rebooting.” After 10 minutes have elapsed, go back to the breaker box and flip the HVAC breaker(s) back on.
A furnace limit switch is a component of a forced-air furnace that is responsible for turning on the furnace blower once the desired heat has been met inside the furnace. Without a functioning furnace limit switch, a furnace would not be able to regulate the temperature in conjunction with a thermostat.
A furnace that's running non-stop is not necessarily bad. During the coldest days in winter, it is normal for a furnace to run almost constantly to keep the home warm.
Here's Why Your Furnace Won't Turn Off. The short answer is your furnace won't turn off due to some kind of error or malfunction within your furnace, thermostat, or HVAC system. It could be the wrong thermostat setting is being used, a clogged air filter or your thermostat itself is no longer working properly.
No fixed duration for how long a furnace should stay off between cycles. But, aiming for three to six cycles per hour in cold weather conditions is a good guideline.
If your furnace is well maintained and working properly, it will typically perform two to three heating cycles per hour with each cycle lasting for around 10 to 15 minutes. That being said, there are a few different factors that can affect either the length of each cycle or how many cycles the furnace has per hour.
The simple solution: Turn your furnace off and check the filter. If it's dirty or it's been 3 months or more since you changed it, put a new, high-quality filter in place.