The Basics of Natural Gas Furnace Operation

A natural gas furnace is a heating system that operates using natural gas as its primary fuel source. The furnace works by burning natural gas in a combustion chamber, which creates hot air that is then distributed throughout the building using ductwork and vents.

The furnace is typically located in a central location in the building, such as a basement or utility room, and is connected to a natural gas line. The natural gas is piped into the furnace, where it is mixed with air and burned in the combustion chamber. The heat that is generated by the burning gas is then transferred to the air that is blown over the heat exchanger, which then distributes the warm air throughout the building.

Components of a Natural Gas Furnace

A natural gas furnace is made up of several key components that work together to create heat and distribute it throughout the building. Here are the main components of a typical natural gas furnace:

Thermostat: The thermostat is the device that controls the temperature of the building. When the temperature drops below the desired level, the thermostat sends a signal to the furnace to turn on.

Burner: The burner is where the natural gas is burned to create heat.

Heat Exchanger: The heat exchanger is a component that transfers heat from the burner to the air that is blown over it.

Blower: The blower is a motor-driven fan that blows the warm air produced by the heat exchanger through the ductwork and into the building.

Ductwork: The ductwork is a system of pipes that distribute the warm air throughout the building.

Vents: The vents are the openings in the building that allow the warm air to enter the rooms.

Natural Gas Furnace Operation

Now that we have covered the main components of a natural gas furnace, let’s take a closer look at how the furnace operates:

The thermostat senses that the temperature in the building has dropped below the desired level and sends a signal to the furnace to turn on. This is done by opening an electronically controlled gas valve.

Natural gas and oxygen and mixed at a specific rate. The mixture enters a series of gas burners. An ignition source ignites the mixture which creates a flame. We call this process “combustion”, and it occurs in the combustion chamber, which is usually at the bottom on the heat exchanger. Combustion gas is safely vented to the outside via a venting system.

The flame heats up the heat exchanger. When a predetermined temperature is reached inside the heat exchanger, the furnace’s blower (fan) is turned on and air is forced through the heat exchanger. Heat is transferred from the heat exchanger to the air blowing through it.

The warm air through the ductwork and out of the vents. As the warm air is distributed throughout the structure, it raises the temperature until it reaches the desired level. Once the temperature reaches the desired level, the thermostat sends a signal to the furnace to turn off. The gas valve closes, stopping the flow of gas. The burner shuts off and the blower motor stops blowing air once the heat exchanger cools off.

Combustion Gas Venting System Operation

The gas created by the combustion process is known as Combustion Gas (it may also be called Flue Gas). The gas is exhausted to the outside through the Venting System. The venting system may include pipe, fittings, and mounting hardware. The venting system may include a Vent Stack. A vent stack can be a chimney, a vertical pipe, or similar structure through which combustion gases are exhausted to the outside air. A vent stack is also known as a smokestack, flue-gas stack, stack, chimney stack, or simply as a stack.

Combustion gas is very dangerous and must never be allowed to enter an occupied area. The air created by the blower must never come in contact with the combustion gas. These two things are carefully isolated from each other.