7 Furnace Safety Features to Stay Safe in the Winter

When the cold fronts start rolling in on the Texas Gulf Coast, many of us begin to think about furnace safety and what maintenance might be needed. Turning on the furnace attached to your central air system is one way to keep everyone toasty warm.

Today’s furnaces have more safety features built-in than ever before. Still, yearly heater tune-ups and inspections are one way to make sure your heater is operating efficiently and safely.

How do furnaces work?

Modern furnaces burn fuel, natural gas or propane, to heat the air which is distributed via fans throughout the home. When the thermostat calls for heat, the furnace creates warm air and blower motors send it throughout the ductwork in your home so every room can stay warm. In other parts of the country, you might see furnaces fueled by coal or heating oil.

Because furnaces are an appliance that relies on combustion, more safety features are built-in to prevent high temperatures that could cause a fire and the build-up of carbon monoxide. When a furnace is in good working order, carbon monoxide and other exhaust fumes are ventilated outside the home through the flue pipe system.  

Other sensors and limit switches spring into action to ensure the flue pipe is clear and inducer fan is running, monitor the presence or absence of a flame, and automatically check the fan to distribute conditioned air is operating. These sensors also make sure the fire is where it is supposed to be and not rolling out of the cabinet, and they can shut down the system if it is overheating. 

Here’s what you should know about safety measures in your furnace. And what else you can do to keep your furnace in good working order.

Safety Feature #1 – Furnace Pressure Switch

Burning fuel for heat results in exhaust, which needs to be safely removed from the home. The furnace pressure switch monitors the air pressure from the fans, called draft inducers. These fan motors pull the flame and flue gasses through the heat exchanger. After the fuel is burned, the fans push the resulting exhaust through the flue pipe system up through the roof. This circulation of air ensures that all the exhaust is being safely removed from your home.

If your flue pipe, which is where the exhaust exits your furnace and your home, is blocked or the fans go out, the furnace pressure switch will trip and cut off the furnace. The switch trips and turns off the furnace because it cannot operate safely without the exhaust system in place. Turning off your furnace will prevent the build-up of exhaust and heat in your furnace’s combustion chamber. 

If this switch trips, contact a licensed HVAC technician who can get to the bottom of the issue and get your furnace running again. Sometimes lack of maintenance can cause this switch to fail.  

Furnace Safety Feature #2 – Furnace Flame Sensor

A furnace flame sensor is a safety feature that switches off the gas supply if it detects the gas is not burning. 

Most modern furnaces have a furnace flame sensor that detects if there are problems with the igniter or spark ignition, the system that turns on the gas and automatically lights the flame when your thermostat says: “More heat, please!”

All of the new furnaces these days use instant ignition to start the furnace.  The only time a flame is present is when the thermostat is calling for heat. While many of us may remember having a pilot light with a thermocouple from furnaces we grew up with, standing pilots have been phased out for improved safety and efficiency.

A furnace flame sensor turns off the gas if a flame isn’t ignited,  so there is no danger of gas build-up or an explosion.  If you hear your furnace start to turn on and a lot of clicking noises, there could be a problem with your igniter and your furnace flame sensor could be tripping.

If this sensor trips, we recommend calling a licensed HVAC professional to come out and find out the root of the problem.

Furnace Safety Feature #3 –  Flame Roll-out Switch

Your furnace also likely has a flame roll-out switch to monitor the flame and ensure it stays in the combustion chamber. It is called a roll-out if a flame enters another part of the furnace. That situation as you’d expect is dangerous and can cause a fire. 

If your flame rollout switch keeps tripping it’s usually indicative of a serious problem.  It could be caused by a blockage in the heat exchanger, a failed heat exchanger, or improper gas pressure. These are the most common causes a flame roll-out switch will activate.   

We advise you call a licensed professional to inspect your furnace and troubleshoot this problem immediately. 

Safety Feature #4 – Furnace High Limit Switch

Every furnace has a high-temperature limit switch, upper limit switch or furnace fan limit switch that prevents your furnace from overheating. The furnace limit switch works like a thermometer. This furnace sensor tests the air above the heat exchanger and turns the fan on when the air is warm enough to circulate around your home to raise the indoor air temperature.

In addition to turning on the blowers to share that warm air, the sensor also can turn the furnace off if it detects the furnace is overheating. This can prevent a fire. 

We see furnace high limit switches activate more often in homes that use zoned systems and when we have a cold snap that persists for some time. Essentially, you have a furnace that is bigger than one zone can handle and it overheats. This circumstance can require some adjustments to the zones.

Again, do not try to bypass safety systems on your own. Rather, call your favorite HVAC technician who can investigate the cause of the issue and restore your furnace to good working order. 

Furnace Safety Feature #5 – Surge Protector

While not built-in to your furnace, one or more surge protectors are an important safety feature your furnace and central air system should have to protect it from power surges, flickers, or brownouts. Electrical parts are particularly vulnerable to power spikes and outages. We recommend surge protectors which are installed as an accessory, especially for ultra-high-efficiency furnaces and HVAC equipment.

Though furnaces create heat by burning gas, their fans and sensors require electricity. This is why your furnace will not operate if your power is out. Working with gas and electricity is a good reason to hire a licensed professional who can troubleshoot and fix what might be going on.

Safety Feature #6 – In-duct Smoke Detector

While often used in commercial settings with equipment blowing more than 2,000 cfms, in-duct smoke detectors are required by some Houston, Texas and surrounding area municipalities for residential and commercial applications. These smoke detectors are located inside of the air ducts, so they are an accessory that is an add-on to a central air and heating system. If these devices detect the presence of smoke, it shuts down the blower motor to limit the spread of smoke throughout the home to prevent smoke inhalation.

On the negative side, in-duct smoke detectors require maintenance, testing, and regular cleaning. Because they are located in-duct, it takes more labor to maintain them. If they are set off by something minor, such as burnt toast, it will require a service visit by a professional.

Some Houston area municipalities require these types of smoke detectors, including as of this writing, West University, Southside Place, Bunker Hill, and others. They are not a replacement for smoke and carbon monoxide detectors distributed throughout your home but they can add an additional level of safety in the event of a fire.

Safety Feature #7 – Smoke and Carbon Monoxide Detectors

Most homes have multiple appliances or features that create heat by burning fuel. Consider your gas oven, water heater, furnace, clothes dryer, and fireplace. In good working order and well-ventilated, these appliances are perfectly safe.

However, house fires and instances of carbon monoxide poisoning can happen. Why take the chance when an inexpensive smoke and carbon monoxide detector can provide an elevated level of safety for your furnace and all of your indoor appliances.  A smoke and carbon monoxide detector at a minimum should be in every single bedroom. You can purchase these separately or purchase a detector that includes both a smoke and carbon monoxide detector inside.

Smoke detectors

Did you know that your city might even install a smoke detector for you at no charge? The Texas Department of Insurance lists smoke alarm programs for cities all over Texas. Here’s a few cities that install or provide smoke detectors for cities in our service area:

Carbon monoxide detectors

If a furnace has a clogged exhaust pipe (also called a clogged flue pipe) or the heat exchanger cracks, carbon monoxide can build up in the home and cause illness and death. Carbon monoxide is a by-product of incomplete combustion which is why HVAC technicians look at the color of the flame as one of the tests they do when they are inspecting your furnace during a seasonal tune-up. The flame should be blue, with no yellow or red flames which indicate incomplete combustion. We have done thousands of furnace tune-ups, and we carry a carbon monoxide detector on our person as we perform every furnace inspection for safety. While we have seen fewer carbon monoxide problems with furnaces that put us in immediate danger, we do frequently spot carbon monoxide problems with water heaters during our furnace checks. 

Some 50,000 Americans each year according to the Centers for Disease Control visit the hospital emergency room because of accidental carbon monoxide poisoning. 

This is why HVAC technicians always recommend having a smoke and carbon monoxide detector in your home. You can easily install them yourself or ask your technician if they can add one or more for you. Our technicians at Terry’s A/C & Heating keep these regularly in stock on our trucks.

Schedule Your Furnace Maintenance in the Fall

A seasonal inspection and furnace tune-up is what we recommend to spot any areas of concern well before they become problematic. There are HVAC maintenance tasks that homeowners can do, such as changing air filters and checking the batteries in your smoke and carbon monoxide detectors, and some areas best left to a licensed HVAC professional.

It is never okay to hear from an HVAC technician that they recommend bypassing safety features of your furnace for any reason. If someone tells you to bypass a safety feature, think twice and get a second opinion because your safety is paramount.

A good question a homeowner can ask is, “Is my furnace safe to operate?” We have heard of some firms that imply a furnace is bad because it has a little rust, giving homeowners the mistaken impression that their furnace could be dangerous and should be immediately replaced. Furnaces that are not operating safely are required by law to be disabled or  “red-tagged.” If your technician will not condemn your furnace, then you may not need to replace it right then.  Even furnaces that would require condemnation can be repaired sometimes, though sometimes replacement is the best choice when the equipment is older or parts are difficult to obtain.

Terry’s A/C & Heating, located in Richmond, Texas and serving Far West Houston and communities in Fort Bend County, offers a scheduled maintenance plan called the Peace of Mind Protection Program that can make scheduling your furnace tune-up quick and easy. Give us a call at 281-495-7830 to set up an appointment today or call us if you’d like a second opinion or quote on a new furnace. We’d love the opportunity to keep you and your family comfortable.

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