Ever wondered what happens on the inside of your furnace? It's important to know how a home furnace functions so you have a good idea what to do when something goes wrong, and when to call for help.
Since the majority of today's home furnaces are gas (heat pumps are a subject for another post), we're going to specifically talk about how the gas furnace works, and what you need to know about their components. Let's take a look at the process!
Gas Supply Line
The gas has to come from somewhere, right? The gas supply pipe is usually located under or to the side of the furnace. It pumps either natural gas from a local infrastructure or propane from a nearby tank, depending on the gas setup. It's good to know where the supply line is and where its shutoff valve may be, in case you ever need to shut off gas to your furnace.
Burners and Pilot Light
Now the gas has to be ignited! This is the job of the pilot light, a small light that typically sits behind the burners on a furnace or gas fireplace. This small blue flame is typically kept alight by a trickle of gas devoted to sustaining the pilot light, although sometimes the light goes out by accident, gets blocked off with trace amounts of soot, or gets turned off for the summer. That's why furnaces usually have pilot light controls for turning the light off or re-igniting it. It's important that the pilot light does not go off by accident, which could fill the furnace with unused gas.
When the primary gas line is turned on, the gas is ignited by the already-lit pilot light, and the furnace burners themselves come to life, supplying the heat that the furnace needs. In full house systems, sensors usually turn the burners according to how the thermostat is set.
Today's furnaces don't usually heat the open air — this is inefficient and can spread contaminants. Instead, they use a heat exchanger, which is basically a metal chamber where air from the house passes through. This chamber is just above the burners, so it grows very hot and must be made of very durable materials. The heat passes from the burner flames to the metal of the exchanger, and then into the air waiting there, quickly heating it up.
The Fan System
Now the heated air needs to move throughout the house or building! This is often done through a fan system located in the furnace, and a series of ducts that connect to the rooms in the house. The fan blows the hot air out into the rooms while using another duct to draw in the cold air for more heating. Most of the noise you hear when the furnace is on is the fan system working.
Looking for more information specific to your furnace, or considering a replacement? Give us a call at Action Heating and Air Inc. for more information!