furnace work

Furnace 101: How Does Your Furnace Work?

Your thermostat is likely the first thing you check when your home gets cold, but it’s not your thermostat that produces the heat. That important job is done by the furnace, usually situated in the basement. But how do furnaces work and what are some of the common reasons they can break down? To help give you a basic understanding of this essential home appliance, we’re going to look at some of the most important components, explain how they work, and where issues can arise.

Why do we use gas furnaces?

Because of our climate, our abundant natural resources, and our home building standards, nearly all residential in Alberta furnaces operate on natural gas. The benefit of gas furnaces is their reliability, relatively easy maintenance, and superior efficiency. Most new gas furnaces have an efficiency rating between 90% to 98%. What does that mean? A furnace with a 98% efficiency rating will transfer 98% of the heat produced during the combustion of natural gas to heat in your home, (while only 2% is lost to the exhaust). In comparison, upwards of 30-50% can be lost on older, mid-efficiency, and standard-efficiency furnaces. Today’s high-efficiency furnaces not only keep your home consistently warm, but they also help reduce your gas bill.

How do gas furnaces work?

Your thermostat serves as the brains of the operation. You set it to the temperature you want in your home and the thermostat signals to your furnace when your home drops below that set temperature. When that happens, your furnace kicks into action. It works by first drawing in fresh combustion air into the burner box and through the heat exchanger, then igniting the pilot (or ignitor), then opening the gas valve delivering natural gas to the burners. Once the furnace is ignited, the blower motor is engaged, circulating air through the furnace, and then through the vents located throughout your home.

Now that you have a high-level idea of how a furnace works, let’s get into how all the parts work in that process, and the ways they can break down.

Furnace parts: how they work and where they go wrong

A lot like your car, your furnace is made up of all sorts of small parts, each of which serves an important purpose to ensure things run safely, efficiently, and smoothly. But over time these parts can wear out or fail and require occasional repair, maintenance, or even replacement. Here are some of the key components that are essential to your furnace’s performance.

Blower Motor

What it is: The blower motor is what distributes air through the furnace (and air conditioner) into the home. Its job is to blow the hot or cool air through your duct system and out the vents to heat or cool each room.

Common issues: When overworked, blower motors can overheat causing bearings to wear out. Blower motors are wear items, meaning eventually they will fail, but certain factors can accelerate the wear on this part. Most commonly, this happens from poor airflow due to clogged or dirty filters. Once a furnace’s blower motor begins to make noises on startup or during normal operation, it’s a sign that this part is on its way out and should be looked at by a service technician. If the blower motor fails, your furnace will not heat or cool your home.

Inducer motor & blower

What it is: You might not know what this part is, but you may be familiar with its sound. This important component is made up of a small, electrical motor, a blower wheel, and an inducer housing assembly. The inducer motor is effectively a fan that circulates combustion air into the furnace heat exchanger. You may recognize this part by the gentle whirring noises you often hear right before your furnace turns on. This is your inducer motor purging air and gas from previous cycles prior to starting the new ignition cycle. The inducer runs whenever the furnace is producing heat and is responsible for bringing in the correct volume of air to the furnace for complete, clean combustion.

Common issues: Like all motors, this component can wear out over time. One of the easiest ways to tell if there is a problem is to listen carefully to your furnace. A burnt-out or worn, inducer motor will often be noisier than normal and produce a higher frequency sound. The same can be said of the blower itself. When it is off-balance or worn, the blower will be louder than normal. A general rule of thumb is that if your furnace is making unusual noises, it is worth calling a professional and scheduling an inspection.

Igniter & pilot light

What it is: The gas that fuels your furnace needs to be ignited to create a flame, which keeps the burner running (think of this like a gas, or a camping, stove). This combustion of natural gas is what creates heat in the furnace’s heat exchanger. At one time, gas furnaces were kept lit by a pilot light (a constant flame inside the furnace burner assembly). However, today all high efficiency, natural gas furnaces do not have pilot lights and instead use electric igniters.

Common issues: Pilot lights can go out due to drafts – meaning you occasionally have to relight them. Also, thermocouples (a safety mechanism that ensures the pilot light stays on) wear out over time and occasionally need to be replaced. Igniters are more reliable but can fail as often as every 5 years if not sooner. Regularly changing your furnace filters can improve the life span of your igniter by keeping it from getting dirty and dusty.

Flame Sensor

What it is: This component is present on mid-efficiency and high-efficiency furnaces and takes the place of a thermocouple. The flame sensor is a safety feature designed to ensure natural gas is always being burned. If the ignitor fails, or the natural gas fails to ignite when the gas valve opens, the flame sensor will alert the furnace to shut off the supply of gas to the burners from the gas valve.

Common issues: Flame sensors rarely break, but they can certainly get dirty from carbon built-up. This reduces the effectiveness of the sensor, causing it to send a message to the furnace that there is no flame present even when the burners have ignited. This can be prevented through regular filter replacement, and annual maintenance or tune-up appointment to clean the sensor.

Note: All homes should be equipped with carbon monoxide detectors. Like a fire alarm, they will beep and alert you if there is a natural gas leak in your home. 

Gas Valve

What it is: The gas valve controls the flow of gas released to the burners for ignition by the pilot light or igniter. In older furnaces, there are two parts: the pilot tube valve which controls the release of gas to the pilot light, and the main valve which releases gas to the burners.

On newer, mid-efficiency, and high-efficiency furnaces there’s only one valve that allows gas to flow to the burners when there’s a call for heat. Higher-end furnaces offer two-stage and modulating gas valves. These vary the flow of natural gas, allowing the furnace to vary the amount of heat output.

Common issues: There are a number of reasons these valves can fail. The most important thing to know here is that a professional service person needs to be brought in if you suspect your gas valve has failed. They will be able to determine if it’s the gas valve or another component that has failed and will be able to safely replace it while preventing possible gas leaks.


What it is: The furnace burner is where the combustion air mixes with the natural gas and is ignited to produce the heat that gets transmitted throughout your home.

Common issues: Burners rarely fail but do get dirty which can cause incomplete combustion of natural gas and reduced energy efficiency. This can be corrected (and prevented) through regular professional furnace tune up’s.


What it is: The furnace filter is a component built to clean the air entering your furnace of dust, dirt, pet hair, and any other particles. This is important to ensure that these particles don’t damage your system through buildup. Some filters also work to improve home air quality depending on your furnace and filter type.

Common issues: Filters are not meant to last forever. They need to be replaced every 30 to 90 days (depending on the filter) or they will quickly become clogged and ineffective. Luckily, filters are quite easy to change out yourself and are relatively inexpensive. Learn more.

A final word of advice

As do-it-yourself YouTube videos become more popular, many homeowners are more empowered than ever to tackle projects in their homes. This is fantastic for some basic wear and tear issues; however, we strongly caution you to call a professional for your annual maintenance check and repair work. In some cases, performing your maintenance may void your warranty.

A yearly check-up can significantly increase the life of your furnace, so be sure to schedule in with a professional to avoid a costly replacement sooner than necessary.

It takes some training and serious know-how to technically understand each part of your furnace, but it’s good to have the general knowledge to keep an eye out for issues. If you suspect something may be wrong with your furnace, or if you’d like to schedule general maintenance, reach out to us today. We’re always happy to help.

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Furnace & Duct Cleaning Checklist




Quote guarantee

When we receive an online furnace or air conditioning quote request and the customer accepts the initial quote, we’ll send a comfort advisor to confirm the provided information and quoted price in person. 


If the comfort advisor finds any inaccuracies during the in person visit, we’ll revise the quoted price on the spot. After the quoted price is confirmed with an in person visit, the price is set. 


If there are unforeseen complications on the date of install, Advanpro will not pass the additional costs along to the customer. (See exceptions in Terms below.)



The guarantee is not valid if the customer provides inaccurate information when Advanpro seeks to confirm any information about the quote. This also applies to the on-site confirmation visit. 



In the exceptional circumstance that the chimney liner required for most furnace installations cannot be installed or gets stuck during installation, the guarantee no longer applies and we will provide a supplementary quote to complete installation. 


We do not warranty or guarantee customer-supplied thermostats.

Repair guarantee

If the diagnosed issue is not fixed by our initial repair, we will dispatch the first available service technician to return and fix it at no additional cost.


If we determine that there is an additional unrelated issue, there may be a charge for the additional repair.

Correct A/C sizing guarantee

If the air conditioner Advanpro installs is determined to be improperly sized for your home, we will supply and install the correctly-sized A/C condenser at no additional cost. 


Advanpro must be immediately notified of any install issues. The guarantee applies for 3 months, starting from the installation date. The guarantee no longer applies if, at any time after the quote or installation, modifications are made to the home that impact cooling requirements.

Correct furnace sizing guarantee

If the furnace Advanpro installs is determined to be undersized for your home, we will supply and install the correctly-sized furnace at no additional cost. 


Advanpro must be immediately notified of any install issues. The guarantee applies for 3 months, starting from the installation date. The guarantee no longer applies if, at any time after the quote or installation, modifications are made to the home that impact heating requirements.

Hot water tank types

Natural draft or atmospheric vented hot water tanks have a 3″ – 4″ steel vent pipe, which runs to a vertical chimney. The chimney is usually shared with standard or mid-efficiency furnaces.


Power vented hot water tanks have one or two black or white plastic vent pipe(s), which are 2″ – 3″ in diameter. The vent pipes usually exit from the side of the house.

A/C Tune Up

Regular preventative maintenance improves efficiency and extends the lifespan of your air conditioning system, with the following benefits:


  • Reduced electricity bills and operating costs. When the unit operates as designed, electricity usage is reduced.
  • Maximized cooling capacity. Home comfort on the hottest of days with minimum run time.
  • Minimized repair bills. Detect and fix small problems before they get worse.

HRV Cleaning

In Calgary, all homes built in 2016 or later have a Heat Recovery Ventilator (HRV). Some homes built or renovated after 2013 may also have an HRV. 


An HRV efficiently replaces stale indoor air with fresh outdoor air, all year round.


As with any other air-handling equipment in your home, your HRV should be cleaned regularly to ensure the best possible indoor air quality.


If you aren’t sure if you have an HRV, call our team to find out how you can tell.

Duct Work Sanitizing

If you or your loved ones suffer from respiratory issues or allergies, or you’re concerned about the quality of the air that you are breathing, then our sanitizing treatment will give you the reassurance that your ductwork is sterile and free of debris that could negatively impact your respiratory and overall health.


Microban is our hospital-grade sanitizing solution, which kills 99.99% of germs, viruses, funguses, molds, and other pathogens.


We also offer Benefect, an all-natural sanitizer made from plant extracts, which also kills 99.99% of germs, viruses, funguses, and molds. ​

Exhaust Flu Stack Cleaning

Mid-efficiency furnaces produce a sand-like, mildly-corrosive byproduct. This substance condenses in the exhaust flu stack and collects over time near the inducer/venter motor, restricting exhaust gas flow. Eventually, it enters the inducer motor and causes premature wear on the furnace.


Exhaust flu stack cleaning removes the build-up to reduce the chance of motor failure and maximize the life span of your furnace. Preventative maintenance ensures your furnace runs efficiently all Winter long — without costly no-heat emergencies. 

A/C + High-efficiency Bypass

The secondary heat exchanger in a high-efficiency furnace or A/C coil has delicate, closely spaced fins that must be protected during your furnace and duct cleaning.


For furnaces that require a bypass, we temporarily install a filter above the heat exchanger or A/C coil, and position our duct vacuum above the filter.


This bypass procedure prevents damage by ensuring all dust and debris in your supply duct work is collected before reaching the heat exchanger or A/C coil.


Standard furnaces without A/C don’t have secondary heat exchangers or A/C coils and don’t require the bypass procedure.

Furnace Tune Up

Regular furnace tune ups are essential to maximizing the lifespan and efficiency of your furnace, so you can rely on it to keep you warm all Winter long.​


During our 30+ point inspection, we check all furnace systems to identify components that are worn out and need replacement. Replacing parts before they break — preventative maintenance — maximizes heating efficiency, avoids no-heat emergencies, and saves on costly service calls. 


Home furnaces can last for 20 years or more if well-maintained. A professional furnace tune up every two years helps to preserve your investment for decades.

Reverse Octopus Whip Tool

The reverse octopus whip has eight 16” flexible tentacles, which whip around blasting high-pressure air in all directions as it moves through your duct work.


The tool agitates and dislodges the most hard-to-reach dust, debris, and contaminants, moving them toward our duct vacuum for collection and disposal.

Brush Cleaning Method

Our high-speed rotary brushing equipment sweeps the entire interior surface of your duct work, ensuring that all dust, debris, and pet hair are vacuumed away.


Physically cleaning the entire length of your duct work ensures that no contaminants are left behind, increasing your indoor air quality and peace of mind.

Dryer Vent Cleaning

Dryer fires are a top-five cause of house fires. Cleaning your dryer vent regularly greatly reduces the chance of a dryer fire, plus the following benefits:


  • Reduces clothes drying times
  • Lowers utility bills through greater efficiency
  • Extends the life span of your dryer
  • Lessens the amount of allergens in your house

Back Skipper Tool

The back skipper is a 1” diameter rounded ball connected to a long, flexible high-pressure airline.


The 1” ball has jets that discharge high-pressure air, pulling the tool and airline through the length of your duct work.


The high-pressure air moves the dust and debris toward our duct vacuum, where it is collected for disposal.​