How to Tell if Your Gas Furnace is Operating Properly
Heating Systems Seasonal HVAC Tips
How Does a Gas Furnace Work? Ways to Tell Your Heating System is Operating Properly
According to the American Gas Association, close to half of all furnaces in U.S. homes are natural gas, making them the most prevalent type of furnace in the country. Natural gas furnaces have a lifespan of up to 20 years, can keep up even in extreme cold climates, and are available in high-efficiency models. If you have a gas furnace or are considering one for your home, it pays to understand how it works, and how to keep it in excellent shape. Why? The condition of your gas furnace can have a direct impact on your home’s energy cost and the health and well-being of your family.
Here, we’ll explore what makes gas furnaces different from other types, exactly how they function, what parts they’re likely to contain, and the steps you can take to ensure your own gas furnace is in good working order.
Types of Furnaces
Before we get into how a gas furnace works, let’s better understand the different types of furnaces available to homeowners:
Electric
Electric furnaces utilize electricity to generate and distribute heat within your home. They are popular choices in areas where natural gas is not readily available. Electric furnaces are usually cheaper at installation and have slightly longer lifespans than gas furnaces, but they aren’t as efficient or as effective in colder locations.
Heat pumps are not electric furnaces, though they do run on electricity. The main difference is that an electric furnace generates heat, while a heat pump shifts heat from an outside source (the air, the ground, or water) to the inside air.
Propane
Propane furnaces are a popular choice in rural areas where gas lines can’t be easily accessed. They also require properties that have the space to host a large tank. Propane is a type of gas furnace that is cleaner burning and more efficient than oil. It is also considered safer than some other gas furnaces.
Oil
Oil furnaces operate by burning fuel oil that is stored in a tank outside the home or in a basement. Oil heat is reliable and consistent, but as fuel prices rise, many homeowners are looking for lower-cost options that are more energy efficient.
Natural Gas
Natural gas furnaces connect to gas supply lines and burn that gas to heat the home. Gas furnaces are often considered cheaper to run and more efficient to operate than electric furnaces. Some homeowners with gas HVAC systems also say natural gas furnaces feel warmer and are better in colder areas.
Across these four categories, there are other furnace types and terms you may encounter. Some of those include:
- Forced-air furnaces: This includes any furnace that uses a blower motor and fan to circulate air through the home.
- Condensing furnaces: These are furnaces that use two heat exchangers to extract more warmth from the exhaust gases and water vapor created during the combustion process, and is a very high-efficiency type of furnace.
- Variable speed furnaces: These furnaces have blower motors with adaptable speeds that adjust to meet the heat demand, which offers consistent heat and better control.
How Does My Gas Furnace Work?
Both propane and natural gas furnaces work similarly. The heating process begins with the burning of gas to generate heat. The warm air heats up the heat exchanger. Indoor air pulled from the home is passed over the heat exchanger where it is warmed up to the appropriate temperature, then recirculated throughout the structure via a system of ducts. Heated air then blows out of the air ducts through vents, which raises the ambient temperature of the space. The thermostat registers this temperature change and signals the furnace to kick off. Once the temperature drops, the heating cycle begins again.
Parts of a Gas Furnace
To better understand how your gas furnace works, it’s helpful to know what parts it might contain. Some of those common parts include:
Blower Motor
Even in a gas furnace, the blower motor itself runs on electricity. The blower mechanism is what pushes warmed air throughout the house.
Blower Fan
The blower fan is run by the blower motor, and is what sucks in the indoor air and pushes it over the heat exchanger to be warmed. Often, the terms blower motor and blower fan are used interchangeably to refer to one unit that includes both elements.
Gas Burner
The burner is where gas flows into the combustion chamber and meets the air, allowing the igniter to spark and burn the gas, producing heat.
Combustion Chamber
The combustion chamber is where the gas is ignited and turned into heat. It is a contained space made of heat-resistant materials, and its proper function is critical to furnace operation and to the safety of anyone inside the home.
Igniter
The igniter is the spark that starts the gas burning to generate heat for your home. It often uses electricity to create the spark, or heated metal which is called a hot surface igniter (HSI).
Pilot Light
Pilot lights have been largely phased out in modern gas furnaces, but they can still be found in older systems. The pilot light is a flame that burns constantly and ensures quick ignition once the gas is released.
Flame Sensor
The flame sensor is an important safety feature of a gas furnace. It detects when a flame is present within the furnace’s burner, and prevents natural gas from building up unburned inside the furnace. Unburned combustion gases can lead to dangerous leaks, fires, and even explosions.
Heat Exchanger
The heat exchanger is the heart of the gas furnace. It often looks like a series of metal coils, similar to a radiator, that generates heat by absorbing warmth from the burning gas and then transferring it back into the air.
Thermostat
The thermostat is what signals your gas furnace to kick on and off. It registers the temperature around it and when the temperature drops below the desired setting, it lets the furnace know it’s time to power on. When the desired temperature is reached, the sensors in the thermostat will let the furnace know it can cycle off.
Flue Pipe
Your gas furnace’s flue pipe is what removes any unburned gases from your home, and is a prominent safety feature of your HVAC system. Unburned gas and byproducts are expelled from your home via the flue, which is connected to the outside.
Ductwork
Your air ducts carry heat throughout your home, then return it to the furnace once it’s time to warm it up again. Ducts can run through the ceiling or beneath the floors to distribute heat to various locations. Some duct systems will be zoned, and use dampers to direct airflow only to select areas of the home.
Control Board
Also called a circuit board, your gas furnace’s control board acts as its brain, receiving signals from the thermostat and sending signals to turn the heat on or off. It is also responsible for starting up key electrical processes within your gas furnace, such as starting the igniter and the blower motor.
Tips for Making Sure Your Gas Furnace is Working Properly
Although your HVAC professional can give you the best analysis of your system’s performance, you can still estimate its condition by inspecting it periodically. Take these DIY steps and troubleshooting tips to keep your gas furnace working properly:
Listen for Unusual Sounds
Some furnace noises are created during normal operation. However, loud pings, pops, rumbles, and screeches are not sounds that you’d normally hear from a furnace that’s running as well as it should. Any of these sounds may indicate it’s time to have a professional tend to your system. Remember that total silence is not the norm, either, so if you can’t hear your furnace running at all, that could also be an indication of a problem with the furnace’s blower or other key components.
Make Sure it Passes the Sniff Test
After sitting for a long period without running, you may notice a slight burning dust or dirt smell during your furnace’s first few cycles. These are usually normal, and should dissipate relatively quickly.
Any other odor can signal trouble, especially if you smell gas, burning rubber, or plastic. Natural gas in its pure form is odorless, but gas companies add scent to warn homeowners of leaks. This type of odor is very sulfurous, and is often said to smell like rotten eggs. If you notice an eggy natural gas smell, leave your home immediately and walk away before calling 911 or your gas provider. Turn your furnace off immediately if you smell burning odors other than dust and call your HVAC technician for emergency service.
Conduct Regular Visual Inspections
Make sure your HVAC system looks to be in good condition. Your gas furnace should show no signs of wear, rust, soot, or dirt deposits. When your furnace runs, the color of the flame inside the burner should be blue. If your gas burns yellow, this may indicate it’s not getting enough oxygen and is creating carbon monoxide.
Clean in and Around Your HVAC System
Checking your air filter monthly and changing it when it’s dirty will prolong the life of your system and keep energy bills lower. If you feel that your HVAC system is struggling to keep up, make sure the air filter isn’t excessively dirty or clogged. Be sure to follow this advice in the hotter months as well, checking your outdoor air conditioning unit to ensure you don’t have a buildup of debris that can keep it from running efficiently.
Keep an Eye on Your Energy Bill
Are your utility bills going up, but your home never feels quite as warm as it should? Locate the specified temperature rise for your furnace on a plate inside the blower and test the temperature rise by placing an instant read thermometer in the register closest to the blower compartment. It should be close to what the manufacturer specified. If not, contact your HVAC professional.
Keep Your Gas Furnace in Tip-Top Shape with Airtron
Home heating doesn’t have to be a mystery you can’t solve. In fact, gas heating can give you higher efficiency and warmer indoor temperatures than other types of furnaces — when you understand how it works and how to maintain it. To learn more about the condition of your gas furnace and schedule routine maintenance to keep it up to snuff, contact the pros at Airtron Heating & Air Conditioning today!
