How long should furnace blower run?

Author: Janie Goodwin  |  Last update: Sunday, August 31, 2025

Your blower motor circulates air through the furnace and can provide uniform temperatures. Many people leave their HVAC fan on all day, while others opt for two to three cycles per hour, ranging from ten to 25 minutes, depending on how close to heating or cooling temperatures they are.

How often should a furnace kick on and off?

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.

Should I let my furnace fan run constantly?

Running it continuously may lead to more frequent maintenance and repair needs. However, the added comfort and air quality benefits often outweigh these concerns. Noise: If you're sensitive to background noise, you might find the constant hum of the furnace fan bothersome.

How long should the fan run after the furnace shuts off?

It will stay on for the duration of the heat cycle and then shut off within a few minutes. If you notice the fan runs long after the furnace stops producing heat, you'll have to investigate further.

Why does my furnace run every 10 minutes?

A malfunctioning or improperly placed thermostat can cause your furnace to short cycle. Common issues include: Old wiring or dead batteries: Replace batteries or old wiring to ensure accurate temperature readings.

Should I Run My Furnace Fan or Not?

Is it normal for furnace to kick on every 20 minutes?

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.

Why does my furnace run for 8 minutes then shut off?

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. You should change your furnace filter at least once every three months.

Is it expensive to leave furnace fan running?

The average kWh in the US costs about $0.12 so it costs about $43 per month, or about $520 per year, to run a fan continuously. At this point, it should be pretty obvious that AUTO costs less than ON but let's math it out to its logical conclusion.

What is the typical time the blower fan off delay is set for?

Most are fixed on 30 sec. As for off, some time longer is better, it give a chance to cool down the heat exchanger and left over heat into the house. As for the blower speed for A/C, it may been dropped to match the CFM for the A/C size.

How long is a furnace supposed to run?

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.

Is it better to leave furnace fan on or auto?

Using the “Auto” Setting

Increased energy efficiency by running the fan only when needed. Extended filter life as the fan operates less frequently. Lower energy bills due to reduced electricity usage.

Is it bad for my furnace to run constantly?

When a furnace runs constantly, it probably means that something is dirty or clogged.

Why won t my furnace fan quit running?

If your furnace fan won't turn off, you most likely have one of these 3 problems: Your furnace fan limit switch is set to “manual override” The fan limit switch is faulty and needs to be replaced. There's a problem in your thermostat wiring.

Why does my furnace run for 30 minutes then shut off?

The most common problems that cause a furnace to short cycle include: An overheating heat exchanger. A dirty flame sensor rod. A blocked flue pipe.

How to tell if furnace is short cycling?

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.

How long should heat stay off between cycles?

However, most heat pumps should complete about two to three cycles per hour, with about ten minutes of downtime between each cycle.

How long should a furnace fan run?

If you wonder, “How long should my HVAC fan run per hour?” then the answer is between ten to 20 minutes for two or three cycles. This works best when your home has a mild outdoor temperature. When temperatures shift strongly towards 0 or 90 degrees (heating or cooling), you will need to run the fan longer.

Can I leave my blower fan on all the time?

Some homeowners naturally worry about the risks of a breakdown if they run the fan all the time, but this will not be a concern for you if your HVAC system was properly installed and maintained. The only possible exception here is a very old fan system, which should generally be replaced in the near future anyways.

Why is my blower fan staying on?

The most common cause of a furnace fan running continuously is that the blower setting on your thermostat is set to “on.” This means that the fan will run constantly as long as there's electric power. This will happen regardless of whether or not your furnace is actually heating.

Is it OK to run furnace fan constantly in summer?

Although it is perfectly safe to run HVAC continuously, there are a few times you should shut it down. First, if your home is experiencing high summer temperatures and you have ductwork in the attic. It is difficult for even the best-insulated systems to fight off extreme temperatures.

How long does a furnace blower fan last?

Blower motors are designed to last just as long as your furnace itself, anywhere from 10 to 20 years. Just as with any HVAC system, the better maintained and serviced your equipment is by experienced HVAC technicians the longer it will last and the fewer repairs you'll face.

Why is my furnace blowing cold air?

With a furnace blowing cold air, the first question you should ask is if the furnace has been turned ON. Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.

How long should my furnace run before shutting off?

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.

What temperature to set thermostat in winter?

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.

Can a dirty filter cause a furnace to short cycle?

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.

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