How Your Home Furnace Works

Furnaces use either natural gas or electricity as heating sources, and when your thermostat indicates that your home needs warming, a control board sends low voltage through an ignition switch to activate your furnace.

Heat exchangers convert air and gas to warm air that flows through air ducts, while vent systems add fresh outdoor air into the system to mix with the heated air.

Keep in mind that your home furnace might be covered by home warranty. Learn more about this here:


Home furnace burners are where air and gas combine and burn, providing heat for your living spaces. When your thermostat sends a request for heat, the burner lights and gas flows into its chamber where a hot flame heats the heat exchanger where return airflow is pulled in to be heated by burning gas from the burner and distributed throughout your home via supply ductwork.

Furnaces may be fueled by gas, oil or propane; historically wood and coal-powered furnaces were run without an electrical thermostat – instead, an external firebox and blower fan system operated them; daily maintenance was necessary to clean out ash from their burner area and “clinkers”.

Modern home furnaces typically run on natural gas, using either an LPG tank outside or inside the basement (LPG) or connecting directly to a utility company meter and mainline (natural gas). Most modern furnaces also boast two-stage operation with multiple capacity settings whereas older models usually only support single stage operation that simply turns on or off according to thermostat settings.

Filthy burners pose a fire hazard and could release carbon monoxide into the house. Furthermore, dirty burners reduce furnace efficiency, leading to higher energy bills – yet cleaning them yourself shouldn’t be difficult or time consuming! Fortunately, however, clean burners are easy to maintain!

First, locate your burners. Take pictures to assist with identification when taking apart, as it will make assembly much simpler. Next, use a small wire brush to scrub any carbon build-up from each burner and use compressed air or compressed air blasts to dislodge any remaining gunk that remains.

Lastly, you can use fine steel wool to clean off the flame sensor rod located behind last burner – this sensor detects whether there is an open flame and often becomes covered in soot over time.

After several rounds of cleaning your burners, you should be able to see the flame clearly. If that’s not the case, it could be worth consulting a professional who can assess and make any needed repairs on the whole furnace system.

Heat Exchanger

Heat exchangers in home furnaces serve a critical function – to ensure that combustion fumes produced from burning fuel remain safe for residents to breathe. Combustion produces toxic byproducts such as carbon monoxide, so it is vitally important that this part of your furnace remain in great shape.

Each home contains one and, to keep its working efficiently and safely, professional HVAC technician maintenance should be provided regularly to maintain it optimally.

Heat exchangers of furnaces consist of thin metal tubes connected by thin walls. Their function is to separate the combustion chamber from the blower which distributes heated air throughout your home, drawing in cold air through its exterior surface before quickly warming it before sending it through ductwork to your living spaces.

Due to this separation, combustion gases and breathing air remain completely separate, which is why having a carbon monoxide detector installed is required (and sometimes required by law). Should poisonous flue gases mix with your oxygen supply and lead to carbon monoxide poisoning and death.

In order to prevent this, your heating contractor will perform routine checks such as cleaning the burner, checking for leaks, and performing a smoke test to assess any carbon monoxide levels that might be entering your home. If a problem arises, they can replace an old heat exchanger with a new one to restore proper operation of your furnace.

Furnaces can also serve to deliver conditioned air, and you can outfit yours with an electrostatic filter or HEPA filter to improve indoor air quality. Because forced air systems utilize your ductwork, you could also add an air purifier or dehumidifier that works throughout your entire house.

Cracked heat exchangers don’t usually require worry on your part; usually covered by manufacturer warranties, but to extend their lifespan you can do things such as regularly replacing and cleaning air filters, keeping ductwork sealed tightly, and scheduling maintenance with an experienced heating technician in your area.


The blower is an integral component of your HVAC system that works by moving air from your furnace through supply ductwork and into supply ducts for delivery to other rooms of your home. Installing a new furnace requires this component too!

As soon as your furnace is switched on, a low-voltage signal from your thermostat triggers its blower motor to begin operating and start moving air over its heat exchanger to heat it before being sent through your ductwork and into your home via fan.

Permanent Split Capacitor (PSC) blower motors run at one speed until their thermostat sends another signal to turn them back off; two-stage or variable speed electronically Commutated Motor (ECM) motors on the other hand operate with multiple speeds to adapt to changing temperatures within your home.

As air passes through your ductwork, it may be filtered by a high-efficiency furnace filter to trap pollution and contaminants that would otherwise enter other rooms of your house. Once trapped, these pollutants and contaminants can then be redistributed using a blower system which also helps lower home energy bills.

Some advantages to having a furnace with a blower include reduced energy costs and creating a warmer indoor environment.

Furthermore, its constant movement through your ductwork removes more dust from surfaces in your home, protecting furniture and belongings from dirt accumulation. In addition, its constant air movement also improves indoor air quality by continuously passing it through an HVAC system’s air filter.

If your blower has stopped working altogether, it might be wise to contact an HVAC technician for a diagnostic evaluation.

They can assess if your blower motor requires repair or replacement as well as your HVAC electrical system and ductwork to see what might be causing issues. Logan A/C & Heat Services offers professional recommendations when replacing blowers based on individual homes’ requirements.


Thermostats are an integral component of your furnace. They regulate its operation at the precise temperature you select, dispensing warm air throughout your home to meet heating demands and keeping energy costs under control by preventing unnecessary furnace cycling.

Knowing whether your thermostat is functioning as designed can be crucial, and performing simple tests will let you do just that.

Home thermostats that use electricity are usually simple devices with an on/off thermostat in its cover that features a bimetallic strip thermometer that is set at a specific temperature.

Small electronic devices attached to this thermometer supply pulses that cause its bimetallic strip thermometer to close on two contacts that connect with HVAC units; when these pulses pass, another set of coils and pulses activate or deactivate these contacts and thus switch on or off HVAC operations respectively.

Modern non-digital electric thermostats are programmable and come with additional controls, enabling you to select different temperatures at different times throughout the day. By programming your thermostat you can save money on utility costs by decreasing its on and off time during times when nobody is home using it.

Some home thermostats feature digital displays that show you exactly how much energy your furnace is using in real-time, making it easy to monitor energy use. Wireless thermostats give you remote monitoring capability of indoor air quality and temperature in real time using apps on smartphones or tablets.

If your heating isn’t performing as it should, start by checking the thermostat – make sure it is set to heat and on a higher setting than what your current room temperature is. Next, ensure your vents (louvered openings in walls and floors where air flows in and out) are clear of obstructions such as furniture or other objects and not blocked by them; also, ensure your ductwork is in good condition and that its vents correspond with natural air movement patterns in your room (warm air rising, cool air sinking). Lastly, speak with an HVAC professional to make sure your system is sized correctly.