How Often Should a Furnace Cycle?

Worried about how often your furnace should cycle?

A normal furnace should cycle between 3 to 8 times per hour. Cold weather can cause your furnace to cycle more often as it struggles to keep up with the cold outside temperatures. Your furnace cycling often doesn’t always mean it’s short cycling.

Below you’ll find reasons why your furnace is cycling and how to fix the issues.

Let’s get started.

How Often Should Your Furnace Cycle?

Your furnace should cycle 3 to 8 times per hour. If your furnace is cycling frequently, it could be a sign that your furnace is short cycling.

There are a variety of reasons why your furnace is cycling, so don’t jump to conclusions before you diagnose the issue.

You can find more reasons why below!

Why Your Furnace is Cycling Often

Furnace is the wrong size

If you’ve purchased an oversized furnace for your home, the oversized system will cause problems when it attempts to heat a smaller sized home.

Symptoms of an overly large furnace are temperature imbalances, excess noise, humidity issues, and higher utility bills.

You have an old furnace

Your furnace may just be nearing the end of its lifespan. With an expected life of 15-20 years, it may be time to have it replaced.

If you aren’t sure how to diagnose an old furnace, then you should look into hiring an HVAC technician to do a check-up.

Furnace is overheating

A clogged filter will lead to restricted airflow which can cause furnace cycling.

Replace the filter and sure that there aren’t any blocks in the ducts.

Thermostat is broken

If your thermostat malfunctions, it’ll signal a furnace cycle.

Ensure that your furnace is following your thermostat’s settings.

If your thermostat is too close to a heat source, then it might not be able to detect the temperature properly.

Dirty flame sensor

An indication that your flame sensor is dirty is that your furnace will cycle for a few seconds at a time. Clean your sensor and see if your furnace continues short cycling. Cleaning the sensor also will prevent harmful gas leaks.

It’s really, really cold

Colder temperatures will require your furnace to work longer to reach your desired temperature.

It’s possible that the outside air temperature is so cold that your furnace is struggling to keep up. This will cause your furnace to continue working and may seem like it’s short cycling but it’s functioning normally.

Heat exchanger is broken

If your heat exchanger is cracked, warped, or broken, then it can increase the time it takes for a furnace cycle, causing a short cycling.

Your heat exchanger is responsible for transferring the gas flames to the incoming air to heat your home.

How long should my furnace stay off between cycles?

A furnace cycle should run anywhere between 10 to 20 minutes.

If your furnace cycles 4 times an hour and runs for 10 minutes at a time, it should stay off for 5 minutes in between each cycle.

Your results will vary as outside air temperatures will dictate how long your furnace cycles.

What is considered short cycling for a furnace?

A short cycle is when your furnace turns off before it reaches your desired temperature.

If your thermostat to 75 degrees and it shuts off at 68 degrees, that’s considered as a short cycle.

A short cycle can also describe a furnace that shuts on and off too often.

Is Furnace Short Cycling Dangerous?

A furnace short cycling can be indicative that your furnace is overheating, which can be dangerous.

This can reduce the lifespan of your furnace and cause higher energy bills.

In extreme cases, an overheating furnace can cause a housefire.

When to Call HVAC Technician?

If you suspect that your furnace is overheating or cycling too often, you should call an HVAC technician to diagnose the issue.

Constant cycles can cause your furnace to wear out and lead to higher energy bills.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

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