How Do Pilot Lights Work?

Furnaces have evolved quite a bit over the last few decades. Those of you who have lived in rural areas far from gas lines, have nice cabins, or have lived a few decades longer than me might have even used wood-burning furnace in order to heat their homes. Those have largely fallen out of favour; gas and electric furnaces are in, which means we don’t all need a small forest in our backyards. Even gas furnaces have evolved considerably, however, but those with a furnace built in the 80s will probably have an interesting little feature in their furnace; the pilot light.

Pilot lights serve a fairly straightforward purpose in gas furnaces; they ignite the gas that’s flowing through the furnace in order to create heat. When the furnace is turned on, gas flows from a valve into the burner, where it is lit. A small amount of gas is also fed from a valve into the pilot light, which is how it keeps burning all the time.

There does seem to be a bit of a safety problem with the pilot light in this case; if gas is flowing continually to the pilot light, when it blows out, where does that gas go? Were it to just flow freely, it could accumulate throughout your house, hazardous to breathe and even more dangerous if it ignites. Fortunately, furnace manufacturers came up with a pretty innovative solution to the problem; the gas valve is closed when the pilot light is off. You might think it uses an electrical current to do this; that’s astute, but it doesn’t quite paint the whole picture. If your home were to experience a power outage, the valve would still need to be able to shut off; how does it generate the electricity needed to close?

The answer is a fascinating little phenomenon known as the thermoelectric effect. Without delving deep into the physics of it, what you need to know is that when a metal is heated on one side but cooler on the other, an electrical current will flow through it. Using this effect, the pilot light heats a metal in order to create an electrical current that holds the valve open. When the pilot light shuts off, the metal cools, the electrical current stops flowing, and the valve closes. That means every time a pilot light shuts off, the valve will shut too; that’s when you have to press a button on your furnace to open the valve, light the gas to create another pilot light, and wait for the metal to heat up again so the valve can remain open.

Anyone who has had to relight a pilot light knows they can be a bit of a pain! Sure, it’s not as bad as burning wood, but there’s a lot of wasted gas that goes to keeping those things lit, so you should probably upgrade to a better, more fuel-efficient furnace. Get a professional furnace maintenance company to look at your setup and propose heating solutions that will fit your budget!

I just wanted to send a quick thank you letter for the excellent work you did for us installing our new air conditioner.  Everything about the job went smoothly due to your staff’s “Can-Do” attitude and we are super pleased with our purchase.  I had a feeling right from the first call back from Gavin that I was going to be looked after like a valued customer!  Within a couple of business days of that first interaction, Gavin had me scheduled for a visit for a site evaluation and air conditioner selection.  When Michael showed up for the site visit he was right on schedule and he patiently spent over 90 minutes with me helping me decide which air conditioner would be the best fit for me from a cost, size, noise level, energy consumption, and warranty perspective.  After I decided on the right unit for me, we walked through the installation process to make sure everything would physically fit and connect well to my existing furnace, just so there wouldn’t be any problems with where I wanted the new air conditioner located.

When the work crew ascended on our house a couple of days later, again they were on schedule.  Some of the team worked quickly to remove the old air conditioner and clean up that existing installation while others on installation of the new unit at the new location.  The installers were awesome!  They were respectful of our home and our curious little dog.  They cleaned up after they were done including properly disposing of the old existing air conditioner.  They even assisted with the warranty registration process.

I am simply amazed that every step of the process was treated with exactly the same customer first attitude!  It’s rare to deal with a trade where every member of the team is so totally customer focused!

Thank you Provincial! We love our new air conditioner!


Bruce & Karen R.
324 A Keewatin St Winnipeg, Manitoba