A Google Nest thermostat is a fantastic way to keep your home comfortable. You can set your heat to run at certain times and even control it from your smartphone if you come home earlier than usual. It'll even tell you when something might be wrong with your furnace.
Usually, this comes as an alert on your phone that shows the Nest heads up alert: "furnace shuts down within 15 minutes of heating." But what do you do about this?
There are several reasons why you might be getting this alert. Read on to learn what causes these problems and how to fix "Nest noticed your furnace shuts down" within 15 minutes of heating alerts.
Lack of Airflow
A furnace is essentially a fire that heats the whole house. This means that air is necessary for the furnace to work. The furnace tries to start and then shut down when this happens.
These are some of the reasons your furnace might lack airflow and how to fix it.
Dirty Filter
The filter to your furnace is designed to prevent any dirt or debris in the air from getting into your furnace. Otherwise, your furnace could clog and become useless. However, this means that all of that dirt and debris collects on the filter.
When the filter becomes full, the air has a hard time flowing through it. This prevents the furnace from getting the airflow needed to heat the house properly.
The solution to this is to replace your furnace's air filter. Do this every ninety days to ensure that your furnace runs well through the winter.
Dirty Blower Wheel
The blower wheel is part of the blower motor of the furnace. This is why air flows in and out of the furnace in the first place. The blower wheel's job is to push air into the furnace to keep the fire going.
But it can't do this if there's too much dirt on it. Debris piled up on top of the blower wheel causes friction when it moves. This means that the wheel can't move the way it's supposed to.
If your furnace ignites but then shuts down, replacing or cleaning the dirty blower wheel might solve the issue.
Failing Blower Motor
The blower motor is what controls the blower wheel. It determines how long the blower wheel runs and how fast it spins. This is essential to getting air in and out of the furnace.
However, like all machine parts, the blower motor doesn't last forever. It gets old and stops working quite as well as it used it. This causes it to slow down or stop responding entirely.
When this happens, then it's time to replace the blower motor. This gets the blower wheel spinning just as fast as it used to so air can flow through the furnace again.
Failing Blower Motor Capacitor
The blower motor also might not be the issue. If this seems to be the case, you might want to look at the capacitor instead.
The capacitor is the power source for the blower motor. If this fails, then the blower motor can turn the blower wheel. This prevents the furnace from having the airflow needed to heat your home.
So if you're getting a furnace shut down error on your Nest thermostat, then it might be time to get a new capacitor so that the blower motor can start again.
Blocked Return or Supply Vent Registers
The blower wheel pulls the air from the return vents in the home. This cycles air through the house and then back out through the supply vents. That ensures that the house is staying consistently warm.
But this air carries debris that builds up on the air filter and sides of the vents. This starts to restrict your home's airflow and can even become a fire hazard if it gets bad enough.
So it's always a good idea to get your vents cleaned regularly so that your furnace keeps running smoothly.
Flame Sensor Is Dirty
In a gas furnace, the gas is ignited inside a chamber. This creates hot air that is then fanned through the entire house. However, this can also create problems.
If the gas isn't igniting correctly, for example, the chamber can fill up with gas. Then rather than hot air, it's the gas that fans out into the house. There's also the risk of an explosion if the gas ignites later.
Your gas furnace uses a flame sensor to account for this, preventing explosions and gas leaks. The gas is released into the chamber and ignited. The flame sensor creates an electrical current that releases more gas into the chamber.
If there isn't enough electricity to release the fuel, then the fuel stops filling the chamber. This reduces the risk of an explosion since gas can't fill the chamber without the spark to ignite it.
This also means that the furnace won't start if the flame sensor can't produce electricity or read the flame levels in the chamber. So if your furnace shuts down before reaching the temperature that you want, then it might be time to clean your flame sensor.
Oversized Furnace
Believe it or not, your furnace can be too big for your house. A furnace usually takes time to warm up a home. It will run for about twenty or more to warm it up and then stop when the thermostat reads the correct temperature.
However, the larger the furnace, the more heat it produces. This might sound like a good thing at first, but it means that the furnace has to turn on and then back off too quickly—constantly. This causes all of the parts inside of the furnace to get overworked.
This leads to the entire system short-circuiting. The electricity to the furnace fries is no longer able to release fuel or ignite the gas. In many cases, the furnace ignites but then shuts down before the house is warm.
The answer is unfortunately simple: your furnace is simply too large for your house. It's under too much pressure to turn on and off constantly. This causes it to burn out like an old filament lightbulb.
You may want to consider getting a smaller furnace for your home if you're constantly having issues. It's better for your home and your furnace's health.
Clogged Flue Pipe
When your furnace runs, it creates more than just heat for your home. The burning of the gas creates other chemicals in the air that are toxic to humans. This includes carbon monoxide, which can be fatal if breathed in for too long.
The flue pipe serves to resolve this factor. A damper inside the line regulates the air pressure inside your home and out. This effectively draws the toxic fumes and carbon monoxide out of your home instead of circulating it inside for you to breathe in.
But this pipe is also prone to clogs. If you don't have a filter on the outside of it, then it's an ideal place for birds to make a nest, for example. Such clogs would force those same fumes and chemicals to circulate in your home's air system instead of going outside like it's supposed to.
The furnace is also designed to shut off if the pressure from the carbon monoxide and fumes builds up inside the chamber, which prevents this issue. This means that if you have a clogged flue pipe, your furnace tries to start but then shuts down when it can't remove those chemicals. Having your flue pipes cleaned should resolve this if this is the issue.
Damaged Ignitor or Pilot Light Goes Out
For the fuel in the furnace to burn, a spark or small flame is necessary to ignite it. This is usually another smaller gas line that provides enough spark to light the rest of the gas to heat the home. These are the ignitors or pilot lights.
But like all pieces of machinery, the ignitor or pilot light is prone to breaking. This means that the fuel in the chamber won't ignite at all. When the flame sensor notices this, it stops sending electricity to release more fuel.
In effect, you get a furnace that tries to start but then shuts down almost immediately. This will continue to happen as the flame sensor keeps trying to see if the fuel will ignite.
The solution is to fix the ignitor or pilot light as soon as possible. This lets the furnace ignite the way that it's supposed to. This gets the whole house feeling warm again in no time at all.
So if you're noticing your furnace short cycling, then you might want to look at your ignitor or pilot light to resolve the issue.
Bad Heat Exchanger
A heat exchanger is a device that transfers heat from one fluid to another. In the case of your furnace, you're transferring heat from the gas in the chamber to the gas in your entire home.
This is the last stage for heating your home. It moves all of the heat where you and your family will actually enjoy it. That makes your home much more comfortable for everyone who lives in it.
But if the heat exchanger breaks, it isn't able to push the heat out into your home. The pressure builds up inside the chamber and causes the furnace to stop running to prevent an explosion.
This also means that your furnace will stop working. Your house will stay cold no matter how many times you try to turn the heat on. It might even trigger a flame rollout switch, which then needs to be manually reset before it works again.
But you won't get any hot air when it does try to start. So if you're getting a Nest "furnace heads up" notification, then you might want to look at your heat exchanger. Getting this replaced might be the solution, and your furnace will run like new again.
Bad Thermostat Location
Your Nest thermostat does more than just allow you to control the temperature of your home. The device itself reads the temperature of the air around it. This is how it determines when the furnace should be on or off.
The issue is that some parts of your house heat more quickly than others. This means that your thermostat's location is important.
For example, if your thermostat sits underneath a vent, the hot air blows directly onto it. This causes the thermostat to think that the house has already been heated up. When this happens, it'll turn off the furnace prematurely and cause furnace short cycling.
Your Nest thermostat will then send you a notification to warn you that there might be a problem with your furnace. Unfortunately, it's unable to tell you what precisely the issue is.
The good news is that this should be easily fixed. You just need to move the thermostat somewhere in your home that doesn't heat up as quickly. This gives the furnace more time to run before it needs to shut off again.
This will make your home warmer and is better for the health of your furnace.
Fix Your Furnace Shuts Down Within 15 Minutes of Heating Nest Alert Today
If you notice Nest sends you an alert telling you that your furnace shuts down within 15 minutes of heating, then chances are one of these is the issue. Now you don't need to panic whenever you have a problem with your furnace. You just need to find which of the above is the issue.
When you do, Technical Hot and Cold have all the parts you might need at the best prices. Contact us today and see how we can help you fix your furnace yourself.
About the Author
James Clark is the Ecommerce Manager of TechnicalHotandColdParts.com and HVAC Controls Specialist (certified in Tridium and Carrier i-Vu controls) with a decade of experience at Technical Hot & Cold. His extensive background includes service calls, installations, and providing technical support to parts customers. James has been featured in the Washington Post and continues to share his knowledge, helping homeowners navigate HVAC repairs. In his spare time, he's playing music with his children and spending too much time working on his lawn.