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

Using a smart thermostat isn’t just smart for saving on heating costs. It can also alert you if there’s an issue with your furnace.

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

One of the most common 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 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 brief period of time then switches off. This HVAC game of red light, green light prevents your home from being warm and can drive up your energy bill. It can also increase deterioration on your furnace. It may also be more likely to break down and may even need to be replaced sooner.

Without Furnace Heads Up, you might not detect your furnace is turning on and off frequently, because its blower fan might keep running. This feature can recognize power interruptions that occur 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 Regularly

If your air filter is too dirty, it will limit 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 easy to stay on top of replacing your filter by setting up a Filter Reminder on your thermostat.

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

  • Press 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."
  • Choose "Furnace Heads Up" and follow the instructions. Your furnace will run 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 clear the test, something else could be wrong that needs professional assistance. If this happens, call Strand Brothers Service Experts at 512-592-3072 for furnace repair.

Clean or Replace Your Furnace’s Flame Sensor

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

  • Take off 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 higher indoor temperature.
  • When you switch on the heat, the fan will begin running first. You should hear it turn on.
  • The ignitor will start to glow. The ignitor is either on the left or right of the burners, but it varies according to the furnace model.
  • Once the ignitor is warm enough, the gas will switch on and the burners will light.
  • If the flame sensor can’t sense a flame, it’s usually because it’s dirty or malfunctioning. Your furnace will then shut off as a safety precaution. If your furnace is short cycling, you'll observe 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 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 due to the fact an HVAC professional like Strand Brothers Service Experts will be able to clean it without breaking 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 clogged by snow or bird nests, so you’ll want to make sure it’s always clear. If the pipe gets plugged, it can result in your furnace overheating. It could also result in carbon monoxide flowing back into your home, creating a potentially life-threatening situation.

However, modern furnaces have a pressure switch that typically will stop these situations from happening. Families with small children will often find their kids have jammed toy cars, sticks or nuts into the exhaust if it’s in a location that can be reached by tiny hands. Even this small amount is enough to trigger the pressure switch. The irregular flow of air into and out of the system triggers the pressure switch, which shuts down the burners. If this is the root of your problem, you will encounter short cycling and a furnace error code indicating the pressure switch was tripped.

An Expert HVAC technician from Strand Brothers Service Experts can check the codes for you and diagnose the problem. Unfortunately, Nest has not evolved to the point where it can interpret 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 get the message, “Nest noticed that your furnace shuts down within 15 minutes of heating,” you know what to do. At Strand Brothers Service Experts, our Experts have the knowledge to resolve any furnace problem quickly and affordably. What’s even better is that we back our repairs with a 100% Satisfaction Guarantee for one year.* To book your appointment, call us at 512-592-3072 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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