What is that burning smell when turning on the furnace for the first time each year?
As the winter season approaches, a lot of you will turn on the furnace for the first time this year. That can be a very intimidating situation for some people. You may have just moved into your first apartment. Or perhaps you’ve just moved into your new home this past summer. The AC worked fine, but now it’s time to see how the furnace is going to work this winter.
Whether you walk over to the thermostat or turn it on manually, what’s that burning smell the first time you’re turning on the furnace for the year? In this week’s blog, let’s break down the gas furnace, and some of the sounds and smells you get when it comes on for the first time each year.
About Turning on the Furnace
You should understand the nature of the furnace is to provide warm air for your home. And it does that with a gas flame. But that gas flame isn’t just flying around uncontrolled the way it does in a fireplace for example. A very structured flame is sent into the furnace. If the flame were to roll out or overheat the furnace, a series of safety switches will engage, turning off the furnace.
Whether you walk over to the thermostat or turn it on with your smartphone, the sounds and smells that you experience can be confusing. That’s not how the air conditioner sounded when it came on, and that’s definitely not how the air conditioner smelled when it was working.
When the furnace gets turned on, the thermostat on the wall tells the furnace which is in your attic, your garage, or your closet in the hallway to initiate a sequence of events that will ultimately shoot a gas flame into the firebox, or heat exchanger.
Turning on the Furnace: the Basic Parts
There are a few parts that come on before that flame starts to heat the home. The thermostat tells the control board inside the furnace to come on. The control board is the brains of the system that will control the following events.
The first motor to come on will be the inducer motor.
Not a large motor by any means, but it’s the one that gets rid of the fumes spent by the flame that warms your home. The control board and a pressure switch acknowledge that the inducer has come on and is working properly.
The ignitor will come on next.
Usually, it’s a hot surface ignitor made of silicon carbide that glows red hot. About 2500 degrees. The timer on the control board then allows the gas valve to open up and pour a controlled amount of gas over the red-hot surface ignitor.
Creating the Flame
This creates the flame we were talking about earlier, that shoots into the metal firebox, which is better known as a heat exchanger to us technicians. A small flame sensor then verifies the flame is on and sends a signal to the board that everything is burning properly, and the system is safe to continue heating the home.
Blower Fan Comes On
If the flame sensor says everything is okay, the control board then tells the blower fan to come on. The sequence is complete. Warm air will then start flowing into the rooms until it gets to the desired temperature.
That whole sequence of events that happens takes about 1 minute from the time thermostat tells the furnace to start, to the time the blower turns on and gives you heat through your registers.
When the thermostat senses the room’s warm enough, it tells the control board to end the call for heating, which then cuts the flame. Meanwhile, the blower stays on just long enough to cool the furnace down quite a bit, about 60 to 90 seconds. This helps extend the life of the system.
So how does the heat exchanger work? Well, it “exchanges heat” by keeping the flame and its fumes inside the metal box while a fan blows air over the outside of the metal. The heat that comes off that metal and the air from the blower is then carried into your rooms where you feel the warm air.
What’s That Burning Smell?
Folks call in every fall when they’re turning on their furnace for the first time and say the system IS working but there’s a strange smell coming through their vents. Almost like a burning smell. When we get out to their home and verify all the motors are working properly, we let them know something most people don’t know until it’s happened to them.
So what’s that smell the first time you turn on your furnace each season? It’s just a fine layer of dust that’s settled onto the heat exchanger. The dust from your house has made its way past the air filter and blower assembly to the metallic heat exchanger. As the metal heats up, the dust burns off and creates that burnt smell. It can happen the first few times you turn the system on, but after that, you shouldn’t get that burning smell any more.
If the smell bothers you, you can just open the doors or windows to your house and let it vent out that way for about fifteen minutes. But rest assured it’s not carbon monoxide. That odorless gas can only be picked up by a carbon monoxide detector.
If you do turn your furnace on for the first time or ANY time this year and your home’s carbon monoxide detector does go off, don’t just remove the batteries. Don’t treat it like it’s some nuisance alarm, either. Go ahead and step outside of the home and call the Fire Department. Let them come out to make sure everything is okay before going back inside. It might cause a big show for everyone in the neighborhood, but who cares? It’s your family’s life on the line.
If you don’t currently have a carbon monoxide detector on each floor and the main hallways of your house, now would be a good time to pick those up from your local hardware store.
Speaking of detectors in your homes – if you haven’t done so already this year, it’s time to change out the batteries in those detectors around your home. Your local fire department usually will come out for free and help you replace those batteries if you have trouble reaching those detectors on your own. If they won’t and you’re in our area, just provide the batteries and we’d be happy to come out and change them for you. Otherwise, any handyman in your area would be up to the task.
As a reminder, the single-most-important-thing you can do to keep your furnace clean is to change those air filters. If the system can’t breathe in because of a dirty air filter, then it won’t be able to breathe out for you at the supply registers in your rooms either. Again, if you can’t do it because you’re elderly or physically unable to reach the filter, give us a call!
Remove Flammables Before Turning on the Furnace
Another bit of advice we’d like you to consider is to make sure there are no flammables around the furnace. Remember, we said that the furnace is either in the attic, the closet, or the garage. These are common places to store items that tend to be forgotten over time.
A metal flue pipe that gets very hot when the furnace is turned on can be dangerous if left unattended. Broomsticks, cardboard, newspapers, clothing, and other materials can scorch over time if they’re resting on the flue pipe. Setting away from the furnace any flammable varnishes, lacquers, oils, and gasoline will help keep your home safe.
Don’t Wait to Turn on the Furnace
Although you might be nervous to turn your furnace on that first time every year, do it. Turn it on when it’s still mild outside. Maybe don’t wait for the first winter snap to hit before finding out your furnace doesn’t work. If you do wait, you might find yourself at the end of a long line. Other homeowners and property management companies may be requesting service at the same time you are.
Taking Care the Easy Way
If you don’t already have someone coming out to your house each year just to make sure everything is running safely for you and your family, we’d love to be the company that gets to do it for you. Fox Family offers an easy way to automate this. You won’t even have to remember to call us. We take care of it all.
Your furnace runs better when it’s been cleaned and maintained, much like your car. Every Fall or Winter is a good time to get the required maintenance done on your heating system. Don’t have a desire to be on an automatic program? Call for a furnace tune-up. A typical cleaning lasts 45 minutes to an hour and a half. It’s usually about a 30 point checklist, but I’ll go into that on another post.
Turning on the Furnace: a Recap
The nature of a gas furnace is to use a controlled flame to warm your house. It’s done in a VERY controlled way by a series of safety switches. Any unexpected events within the furnace components tell the control board to shut down the unit.
Thanks so much for stopping by, and we’ll see you on the next blog post!