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

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

The Google Nest is equipped with a feature called Furnace Heads Up, which will alert you if it notices a problem with your heating system. You’ll see the warning on the thermostat, in the app and in your monthly Nest Home report.

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

Your Furnace is Short Cycling

When you see the message “Nest noticed that your furnace shuts down within 15 minutes of heating,” that means your furnace is short cycling. Short cycling is when the furnace switches on for a short period of time then switches off. This HVAC game of red light, green light stops your home from being warm and can drive up your energy bill. It can also increase wear and tear on your furnace. It may also be more likely to break down and may even require replacement sooner.

Without Furnace Heads Up, you might not detect your furnace is turning on and off frequently, because its blower fan might keep going. This feature can pick up on power interruptions that take place during short cycling.

How Do I Keep My Furnace from Short Cycling?

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

Change Your Air Filter Often

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

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

  • Press the ring to bring up the Quick View menu, where you’ll select "settings" and then "equipment."
  • The thermostat will show the wires linked to it. Select "continue."
  • You’ll see system components shown. Select "test."
  • Select "Furnace Heads Up" and follow the instructions. Your furnace will go through a 15-minute heating test and give you the results when it’s finished.

Google says if the filter is clean or if your furnace didn’t pass the test, something else could be awry that requires professional help. If this happens, call Bob Brown Service Experts at 623-243-4517 for furnace repair.

Clean or Replace Your Furnace’s Flame Sensor

Having a dirty or malfunctioning flame sensor is another top explanation why your furnace might short cycle. You can tell if there’s a problem by paying attention to your furnace as it turns on. Here’s what to look for.

  • Remove the door from your furnace so you can see the burners. If you have a viewport in the furnace door, you may not have to remove the door for this.
  • Switch on the furnace by setting the thermostat to a warmer indoor temperature.
  • When you turn on the heat, the fan will turn on 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 hot enough, the gas will turn on and the burners will ignite.
  • If the flame sensor can’t sense a flame, it’s usually because it’s dirty or defective. Your furnace will then turn off as a safety precaution. If your furnace is short cycling, you'll notice the flame and fan shutting down after a couple of seconds.

If you’re wondering how flame sensors could get dirty being bathed in fire continuously, a blend of moisture and chemicals in the air form a thin coating of carbon on the surface. Cleaning a dirty flame sensor will stop the short cycling problem. This task is best left to an Expert. That's due to the fact an HVAC professional like Bob Brown 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 outdoors through a PVC pipe. This pipe can get blocked by snow or bird nests, so you’ll want to make sure it’s always clear. If the pipe gets plugged, it can cause your furnace to overheat. It could also cause carbon monoxide to flow back into your home, creating a potentially life-threatening situation.

However, modern furnaces are equipped with a pressure switch that typically will prevent these situations from happening. Families with young children will often find their kids have stuffed toy cars, sticks or nuts into the exhaust if it’s in an area that's accessible by tiny hands. Even this little amount is enough to trigger the pressure switch. The uneven flow of air into and out of the system trips the pressure switch, which shuts off the burners. If this is the root of your problem, you will experience short cycling and a furnace error code specifying the pressure switch was triggered.

An Expert HVAC technician from Bob Brown Service Experts can look up the codes for you and determine the problem. Unfortunately, Nest has not evolved to the point where it can read the error codes furnace manufacturers produce, so you will still require a pro to help you out.

Let the Experts Handle Your Short Cycling Furnace

If you get the message, “Nest noticed that your furnace shuts down within 15 minutes of heating,” you know what to do. At Bob Brown Service Experts, our Experts have the knowledge 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 request your appointment, call us at 623-243-4517 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.

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