If the time between cycles is less than five minutes, the furnace is most likely short-cycling. Heating cycles that run for shorter periods of time produce more frequent heating cycles. Depending on the outside temperature and how well-insulated your home is, these short cycles may occur five to eight times per hour.
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.
If your furnace shuts off after a few minutes and starts more than eight times an hour, it may require repair. Common causes of furnace short cycling include restricted airflow, a malfunctioning flame sensor, or a poorly placed thermostat.
A furnace cycling on and off repeatedly can be caused by various reasons, from dirty filters and obstructions in ducts and registers to incorrect thermostat settings and faulty limit switches. By following the steps above, you can help prevent your furnace from cycling too frequently and save energy costs.
During an average heating cycle, a furnace should operate for 10-15 minutes. If you're wondering how often furnaces cycle, the answer is: it depends. Furnaces in homes with average insulation might run two to three cycles per hour to heat the living space properly.
If the time between cycles is less than five minutes, the furnace is most likely short-cycling. Heating cycles that run for shorter periods of time produce more frequent heating cycles. Depending on the outside temperature and how well-insulated your home is, these short cycles may occur five to eight times per hour.
If your furnace turns on, and off, and back on again in a seemingly endless loop, you're experiencing short cycling. Essentially, short cycling occurs when the system cannot complete a full heating cycle. There's no one cause of short cycling, but with some troubleshooting you can get to the bottom of the issue.
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.
Short cycling is a common sign of a bad flame sensor. The sensor thinks that there isn't a flame, so it shuts off the gas as a safety mechanism. Except, there is a flame and without the gas to supply it, it dies. This is a frustrating problem, but an HVAC technician can fix it.
On average, furnaces should kick on and turn off anywhere from three to eight times per hour.
One of the most common causes of a furnace shutting off unexpectedly is low airflow. If your furnace keeps turning off, check for issues such as: Dirty Air Filters. A clogged filter restricts airflow, causing the furnace to overheat.
It's common for your furnace to kick on more frequently in cold weather. While it's okay if your furnace cycles on and off several times every hour, it shouldn't cycle on and off more than 8-10 times. If it does, this is known as short cycling, and it's a sign that something in your heating system needs to be fixed.
During the coldest days in winter, it is normal for a furnace to run almost constantly to keep the home warm. As long as the furnace is running efficiently and not making strange noises, the constant operation is likely nothing to worry about. But in general, your furnace should not constantly be running.
However, most heat pumps should complete about two to three cycles per hour, with about ten minutes of downtime between each cycle.
A dirty air filter is the most common cause of short-cycling. If the air filter is clogged with dirt, it won't allow proper air flow to the heat exchanger.
Thermostat Troubles Can Cause Short Cycling
Your furnace or central air conditioner spends a good amount of energy simply turning on and off, which is why you want yours to run for at least 15 minutes at a time before shutting off.
Uneven Heating
Inconsistent heating patterns often point to thermostat inaccuracies, as the device struggles to regulate the temperature evenly. On the other hand if the entire house feels uniformly cold then the furnace might be the problem.
In the heating, ventilation, and air conditioning (HVAC) business, short cycling is a phrase used to describe when a heater or air conditioner cycles on and off too frequently. It signifies a problem in your heating system's proper functioning and efficiency, in which it is not completing its heating processes.
But when your furnace won't shut off, the thermostat is often the first place to inspect. A common issue is incorrect settings. Make sure your thermostat isn't set to a constant “heat” or “on” mode, which can cause the furnace to run continuously.
Industry research shows some expected time frames for how long a furnace runs during a particular cycle. 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.
A dirty or clogged air filter will prevent the furnace from delivering the proper amount of heated air to the space and will often cause the furnace to cycle on and off on its over-temperature device.
While moisture and rust are one of the most common causes of delayed ignition in furnaces, dust and lint can also accumulate and cause problems. This can be easily remedied by having your furnace inspected and cleaned by professionals before each heating season.