Solved: Nest Noticed Your Furnace Shuts Down Within 15 Minutes of Heating

Using a smart thermostat isn’t just wise for saving on heating costs. It can also let you know if there’s a problem with your furnace.

The Google Nest has a function called Furnace Heads Up, which will let you know if it detects a problem with your heating system. You’ll see the alert on the thermostat, in the app and in your monthly Nest Home report.

One of the most frequent problems is: “Nest noticed that your furnace shuts down within 15 minutes of heating.” Here’s why this is happening and how you can fix it.

Your Furnace is Short Cycling

When you get the message “Nest noticed that your furnace shuts down within 15 minutes of heating,” it's saying your furnace is short cycling. Short cycling is when the furnace turns on for a short period of time then switches off. This HVAC game of red light, green light prevents your home from heating up and can drive up your energy bill. It can also increase deterioration on your furnace. It may also be more susceptible to breaking down and may even require replacement more quickly.

Without Furnace Heads Up, you might not notice your furnace is turning on and off often, because its blower fan might keep running. This feature can detect power interruptions that occur during short cycling.

How Do I Keep My Furnace from Short Cycling?

There are a few simple ways you can keep your furnace from short cycling.

Replace Your Air Filter Often

If your air filter is too dirty, it will limit airflow. Your furnace will then shut off early to avoid overheating. We recommend changing flat filters once a month, and pleated filters every three months. It’s easy to stay on top of changing your filter by adding a Filter Reminder on your thermostat.

If you’ve changed your filter after receiving a Furnace Heads Up alert, you can do a test to see if that fixes the problem.

Push the ring to bring up the Quick View menu, where you’ll choose "settings" and then "equipment."
The thermostat will display the wires connected to it. Choose "continue."
You’ll see system components shown. Hit "test."
Select "Furnace Heads Up" and follow the instructions. Your furnace will go through a 15-minute heating test and tell you the results when it’s done.

Google says if the filter is clean or if your furnace didn’t clear the test, something else could be awry that needs professional help. If this happens, call Roland J. Down Service Experts at 518-417-2938 for furnace repair.

Clean or Replace Your Furnace’s Flame Sensor

Having a dirty or bad flame sensor is another top explanation why your furnace might short cycle. You can determine if there’s a problem by watching your furnace as it starts up. Here’s what to check for.

Remove the door from your furnace so you can look at the burners. If you have a viewport in the furnace door, you may not need to remove the door for this.
Turn on the furnace by setting the thermostat to a warmer indoor temperature.
When you switch on the heat, the fan will begin running first. You should notice it turn on.
The ignitor will begin to glow. The ignitor is either on the left or right of the burners, but it depends on the furnace model.
Once the ignitor is warm enough, the gas will switch on and the burners will ignite.
If the flame sensor can’t sense a flame, it’s usually due to the fact it’s dirty or faulty. Your furnace will then shut off as a safety measure. If your furnace is short cycling, you'll notice the flame and fan shutting off after a few seconds.

If you’re questioning how flame sensors could get dirty being bathed in fire continuously, a combination of moisture and chemicals in the air form a thin layer of carbon on the surface. Cleaning a dirty flame sensor will stop the short cycling issue. This job is best left to an Expert. That's because an HVAC professional like Roland J. Down Service Experts will be able to clean it without damaging it or be able to tell you if it needs to be replaced.

Check Your Furnace’s Exhaust Pipe Frequently

Your high-efficiency furnace vents combustion gases outside through a PVC pipe. This pipe can get blocked by snow or bird nests, so you’ll want to ensure that it’s always clear. If the pipe gets blocked, it can result in your furnace overheating. It could also cause carbon monoxide to flow back into your home, creating a potentially deadly situation.

However, modern furnaces have a pressure switch that generally will prevent these situations from happening. Families with small children will often find their kids have stuffed toy cars, sticks or nuts into the exhaust if it’s in a location that's accessible by little hands. Even this small amount is enough to trigger the pressure switch. The uneven flow of air into and out of the system triggers the pressure switch, which shuts down the burners. If this is the underlying cause of your problem, you will experience short cycling and a furnace error code indicating the pressure switch was triggered.

An Expert HVAC technician from Roland J. Down Service Experts can look up the codes for you and determine the problem. Unfortunately, Nest has not developed to the point where it can read the error codes furnace manufacturers create, so you will still require a pro to assist you.

Let the Experts Handle Your Short Cycling Furnace

If you receive the message, “Nest noticed that your furnace shuts down within 15 minutes of heating,” you know what to do. At Roland J. Down Service Experts , our Experts have the expertise to resolve any furnace problem quickly and affordably. What’s even better is that we stand behind our repairs with a 100% Satisfaction Guarantee for one year.* To book your appointment, contact us at 518-417-2938 or schedule online.

*Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.