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How Does a Furnace Work?

When people say “furnace” what they are typically referring to is the system in place that heats their home.  While your furnace is likely sitting down in your utility room (commonly called a “furnace room”), know that the system that heats your home is actually a combination of appliances that work in conjunction with one another.

A Typical Home HVAC Setup

Most homes will have a standard HVAC setup, with a furnace and a thermostat.  The thermostat measures the temperature of the ambient air surrounding it.  When it reads an air temperature lower than what it has been set to regulate, it sends a signal to the furnace to turn on.

The two most common types of furnaces found in Calgary are natural gas and electrically powered.  Once the furnace has received the signal from the thermostat to turn on it will take in air via its intakes (called “cold air returns”, found throughout the home), heat the air up, and then send it throughout your home via the duct system.

A Slightly More Elaborate Home HVAC Setup

While nearly all homes in Alberta will have the basic thermostat/furnace combination (save for homes that are heated with alternate sources, such as radiators or solar heating), many feature other components that work in conjunction with the furnace/thermostat to regulate the internal environment.

In addition to a furnace and thermostat your home may also have:

  • A humidifier – Used to regulate the humidity of the air inside your home, a humidifier can greatly increase the ambient air quality.  Alberta (Calgary, in particular) is a very arid province, and a humidifier offers many benefits (such as providing a better environment for wood products, preventing them from warping/cracking from dehydration; keeping your skin moist and comfortable, etc.).
  • Central air conditioning – An air conditioner helps regulate the indoor air temperature by cooling the air if the ambient air temperature rises above the level specified by the thermostat.
  • Air filtration – While nearly all furnaces come with a filter installed, many homes also have separate air filtration systems that improve the indoor air quality.

The Basics Behind How Your Furnace Works

You have your thermostat set to 22°C.  The thermostat will regulate the air temperature by engaging the furnace whenever the temperature drops below your specified amount.

When a modern furnace engages a few things happen:

  • First, the signal from the thermostat is received – Many programmable thermostats will make a “clicking” sound when the signal has been sent.
  • Fuel is then sent to the burners – At the heart of a gas furnace are burners, designed in such a way so as to maintain an even, controlled flame.
  • Once ignited, the furnaces internal sensors check to verify that all burners are lit – If a burner has not lit the entire mechanism will shut down and wait a predetermined period of time (varies based on each furnace) before attempting to reignite.
  • The burners heat a device called a heat exchanger – A heat exchanger more efficiently warms air (compared to the burners on their own).
  • A blower engages to circulate air through the heat exchanger – Once the heat exchanger has reached its operating temperature the blower motor is engaged, circulating air that has been sucked in through cold air returns.  This air is forced over/through the heat exchanger and then sent throughout the home.
  • A network of ducts directs the air throughout the house.

Modern furnaces are far more efficient at this process compared to older, antiquated furnaces.  They also utilize a series of fail safes and safety mechanisms designed to protect both your home and the furnace from failure. Learn more about your furnace from the experts at Action Furnace.

Note that the process for electric furnaces is nearly identical, though instead of burners an electric furnace uses resistance coils/tubing to create heat.

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