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.
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. Outside temperature, for example, could contribute to how fast or slow the furnace cycles.
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.
Furnace short-cycling refers to a furnace that's switching itself on and off too frequently. 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.
A system that has been dormant for months suddenly finds itself working overtime. It should cycle throughout the day. An average furnace should turn on and off three to eight times per hour. If your furnace is turning on and off more frequently, don't assume it is short cycling.
A furnace “short cycles” when it turns off before reaching the desired temperature. This means that if your thermostat is set to 72 degrees, the furnace may shut down at 65 or 68 degrees, but will never reach 72 degrees. Short cycling can also be used to describe a furnace that turns on and off too often.
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.
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.
A high-efficiency furnace should be running at least 80% of the day if not longer.
Typically, a furnace should cycle three to eight times per hour. While furnace cycling is normal, frequent cycling can indicate that your heating is struggling to keep up. We've put together this guide to help you understand the difference between normal furnace cycling and short cycling.
Dirty Air Filters
So, the furnace is triggered to stop, then it cools down only to fire back up again. This short cycling continues to repeat until the furnace receives the airflow it needs. Dirty air filters are one of the most common reasons behind furnace short cycling.
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.
If your furnace is overheating, it could be shutting off prematurely before it reaches your desired temperature when the temperature safety limit is reached. Ensure that your furnace filter is clean and there are no other obvious signs of broken or loose parts inside your unit.
But in general, your furnace should not constantly be running. Otherwise, it could indicate a problem with your heating system. In this case, have a qualified HVAC (Heat, Ventilation, and Air Conditioning) technician inspect your system and address issues that make it run constantly.
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.
So how fast should a furnace heat a house? On average, once you turn on your furnace, it should take about an hour to increase indoor temperature by 1 degree. Afterwards, it's 45 minutes per degree.
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.
The smaller the difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be. You can easily save energy in the winter by setting the thermostat to around 68°F to 70°F while you're awake and setting it lower while you're asleep or away from home.
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.
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.
Furnaces typically run for about 10 to 15 minutes in moderate weather. Extreme cold can result in longer cycle times.
Your thermostat could also cause the HVAC system to cycle on and off rapidly, a process known as short 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.
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.