It's normal for a furnace to turn on and off periodically. They are designed to cycle on and off, but a standard home furnace should only turn on and off between three to eight times per hour. That means normal heating cycles last from seven to 20 minutes.
What Causes Short Cycling? Furnaces have built-in safety systems that prevent dangerous situations like fires, carbon monoxide leaks, or gas leaks. The most likely cause of short cycling is the fan limiter, which prevents fires and furnace damage by shutting the system down if the heat exchanger becomes too hot.
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.
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.
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. But to keep temperatures at a comfortable level during cold weather, a furnace might need to increase this range to three to 10 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.
They are designed to cycle on and off, but a standard home furnace should only turn on and off between three to eight times per hour. That means normal heating cycles last from seven to 20 minutes. You can tell your furnace is short-cycling if that on/off cycle happens every couple of minutes.
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.
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.
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.
However, most heat pumps should complete about two to three cycles per hour, with about ten minutes of downtime between each cycle.
Many homeowners face this common issue which can lead to higher utility bills or costly repairs if not addressed quickly. A furnace that frequently turns off and on, a condition known as furnace short cycling, could be a sign of underlying issues that need immediate attention.
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.
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.
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.
A clogged furnace air filter will negatively affect the airflow throughout your house and HVAC system. The lack of fresh air in your furnace will cause the heat exchanger to become too warm and deactivate. Dirty filters indirectly cause short cycling issues and will make it hard to keep your home warm.
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.
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.
Ask twenty professional HVAC contractors the question, “How Much Does A New Furnace Cost?” and you'll probably get the same answer... “It depends.” On average, the cost of a new furnace can range from $2,000 - $14,2001. However, factors like furnace efficiency, type, size, and much more can impact this range.
Luckily, a few causes of short cycling are easy to fix yourself. An incorrectly sized unit, refrigerant leaks, and other issues demand a professional repair. If your short cycling issues are due to air filter problems or a frozen evaporator coil, you can address the problem before calling the professionals.
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.
When your furnace starts and stops, it could be an indication that you have insufficient airflow. If there is inadequate airflow, the heat exchanger in the furnace will frequently heat up. This problem is more likely to occur if the heating unit is in a congested storage area.
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 having trouble igniting or maintaining a consistent flame, it can lead to short cycling. Common ignition issues include: Dirty or malfunctioning flame sensor: A dirty flame sensor can't detect the presence of the flame correctly, causing the furnace to shut down as a safety measure.