Furnace 101: How They Work & What Are Your Options?

home furnace with a residential gas, water, and heat

Furnace 101: How They Work & What Are Your Options?

When it’s time to choose a new heating system, whether it is a new installation or a replacement for a current HVAC system, one of the best options is a furnace. With several types to choose from offering different fuel sources, understanding how furnaces work ensure the system you choose will fit your individual needs.

What Are Furnaces?

Furnaces are designed for a specific reason — to provide heat throughout a home. Furnaces are also referred to as forced-air furnaces because of the way the system works using a blower to direct and distribute warm air throughout the home or building.

How Do Furnaces Work?

How a furnace works depends on several factors. While each type has the goal of heating air then distributing the heated air via a component through the structure’s ventilation system, there are several differences. Furnace models may differ due to the type of fuel used along with the different methods used for the transference of heat. Different systems may also have features specific to their model to support the performance of the system and energy efficiency.

Types of Furnaces

Several types of furnaces are available, each using a different source of fuel. Some furnace models are operated using natural gas or propane. Other model types operate by using electricity or oil. Some furnaces also use wood as a fuel source.

Gas Furnaces

There is one basic difference in how a natural gas or propane gas furnace operates. With a natural gas furnace, the fuel enters the furnace via an underground connection or pipe to the gas source. A propane furnace requires a dedicated storage tank to hold the fuel. With either type, once the gas enters the unit the burner is activated and begins warming the fuel.

The unit will then use the cold air within the home to generate warm air. This is accomplished when the cold air is blown across the heat exchanger where it is then subjected to the warmth of the burning gas. During the process, vents will expel the exhaust through a flue pipe.

The blower fan then takes over the process by directing the warmed air throughout the building using the ductwork to deliver it to the different supply registers.

As the warm air is distributed, the temperature increases and the cold air is filtered back through the ducts to the furnace. When the set temperature is reached, the thermostat will turn off the valve feeding the gas, which stops the process of continuing to produce warm air.

Benefits of natural gas furnaces include reduced heating costs, lower energy bills, increased efficiency, better reliability, and a cleaner-burning fuel making it better for the environment.

Propane gas furnaces also have benefits, such as affordability, versatility, safety, a high level of warmth, and environmental friendliness.

Electric Furnaces

The basic principle of an electric furnace is the use of a motor to pump cool air to the system. The air is directed to the furnace’s elements where it is heated and then redirected to the ducts. Several components play a role in the system’s operation.

An electric furnace uses a thermostat to control a component of the furnace known as the sequencer. The sequencer is a mechanism that can activate switches to provide necessary tasks for the operation of the furnace. It can allow power to the internal elements, and it can power the fan and blower that directs air over the heating elements or coils, resulting in warm air being directed through the ducts to the registers in each room. When the warm air reaches each room, the register, which will be fitted with a damper, allows the flow of air into each room to be controlled.

Electric furnaces also have a limit switch to ensure safety. The switch senses the temperature of the furnace alerting the blower fan when to turn on or off whenever the system is functioning normally through the heating cycle. If the internal temperature of the furnace gets too high and is overheating, the limit switch shuts down the system.

Electric furnaces have several benefits. These include efficiently generating heat, as an electric furnace does not require a dedicated storage tank, environmental friendliness,  a longer life, and affordable pricing.

Oil Furnaces

Like the propane furnace, an oil furnace also needs a dedicated tank to hold the fuel. Also, similar to electric and gas furnaces, an oil heater operates on the basic principle of converting air drawn into the system into warm air to disperse throughout the ductwork.

With an oil furnace, once the thermostat falls below the set temperature, the furnace is turned on. The activation of the furnace causes the fuel pump to access and draw oil from the storage tank. The oil first passes through a filter then on to the burner chamber where the fuel is changed from a liquid to a mist. The burner is then sprayed with the mist.

As the burner chamber begins to heat to elevated temperatures, air drawn from the interior of the building is also directed to the burner chamber

, so, it too, reaches higher temperatures. The result is hot air that flows out to the duct system to all rooms. Once the temperature reaches what was set on the thermostat, the system will stop cycling hot air until the temperature falls below the desired setting.

Some of the benefits of an oil furnace include equipment that is less expensive than that of a gas or electric furnace, repairs that are less expensive, and that oil is an excellent generator of heat.

Maintaining a Furnace

A furnace is an investment and one that you want to protect. With a maintenance program in place, it ensures your investment, enhances energy efficiency, and extends the equipment’s life. With our program at Legacy Air, systems are well cared for by expert technicians. From guaranteed appointments, two yearly tune-ups, and discounts for parts and services, to less expensive service fees and a lifetime warranty on Legacy Air parts and labor, we help equipment maintain optimal performance.

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