The brains of the operation

To understand how a furnace works to supply heat to your home, let’s first begin with some of the basic components that – when effectively combined -provide warm solace during the cold season.

  • Burners: deliver and burn fuel
  • Heat Exchangers: series of hot, metal tubes that warm cool air as it passes through
  • Blower: device that forces filtered air through the heat exchanger
  • Flue: a channel that vents harmful gases

It All Starts at the ‘Stat

Contrary to what most people may think, the heating process doesn’t start at the furnace itself, but rather from the thermostat. This nifty sensor determines what the current room temperature is, and allows you to adjust it accordingly to maintain a comfortable setting.

Thermostats are pretty intuitive devices. Once it detects your room temperature is below the preferred setpoint, it activates your oil or gas burner; setting off a chain of events that facilitate the heating cycle.

Under Pressure

As soon as the furnace receives the thermostat’s signal to get crackin’, that’s when things start to heat up – literally. Following suit are a series of controlled steps that ensure the safety and efficacy of the heating process. Step one of the operation focuses on activating the venter motor (more commonly known as the ‘induced motor’). Responsible for building negative pressure inside the heat exchanger, this device purges any lingering gases that may have been present from the previous heating cycle; ensuring air quality is suitable at the time of combustion.

Signal ‘da Flame

Now at this point of the heating operation, sensors should indicate enough negative pressure has been built, sending power over to the hot surface igniter (HSI), which will activate after some time. Once it does, the main gas valve opens; permitting gas to flow through the burners, where it is then ignited by the HSI and turning on the main burners.

Thar She Blows

Okay, so once the burners are operating, they heat a metal unit known as the heat exchanger. This gadget transfers heat from the flame to the surrounding air, once a certain temperature has been reached. That’s when the blower motor is subsequently energized. Acting like a fan, the blower is responsible for moving air through the heating system. The heated air is then dispersed through your duct system, supplying individual rooms with that sought-after warmth you crave during those frigid months. As soon as the thermostat recognizes that no more heat is required, the gas valve is de-energized, cutting off the gas supply provided to the furnace.

Round and Round It Goes…

By now, you should be basking in the heated glory that fills your room with comfort. As you sip your cider and flip through late-night TV, you probably don’t realize that once the desired room temperature has been achieved, your thermostat alerts the furnace to take a breather – for the time being, anyway. However, once heat escapes and your house begins to cool, it’s back to the cylindrical drawing board, as the heating process starts all over again. Like a song that plays on repeat, your furnace mimics the same cycle in order to maintain a comfortable temperature.

Final Thoughts

Who knew that from the exterior of that dulled metal shell, an intricate operation was taking place? Like the Domino Effect, each step of the heating cycle affects the entire outcome. If just one component was on the fritz, your furnace would merely be an obsolete box, collecting dust in some darkened basement corner. Hopefully this overview puts into perspective how much work this fella puts in, to ensure your comfort and air quality are at the forefront of its mission.