A home gas furnace is a type of heating system that burns natural gas to produce heat, which is then circulated through the home using a duct system. The furnace consists of several key components, including a burner, heat exchanger, blower, and thermostat.

When the thermostat signals for heat, the furnace's control board activates the burner. The gas valve opens, allowing natural gas to flow into the burner, where it is ignited by an electronic spark or pilot light. The burner produces a flame that heats the heat exchanger, a metal component that absorbs the heat and transfers it to the air passing through the furnace.

Once the heat exchanger is heated, the furnace's blower motor turns on, drawing air into the furnace through a return duct. The air passes over the heat exchanger, where it is heated, and then is blown through the supply ducts to warm the home.

As the heated air is circulated throughout the home, the temperature rises and is detected by the thermostat. Once the desired temperature is reached, the thermostat signals the furnace to turn off the burner and blower motor, and the cycle ends until more heat is needed.

Overall, a gas furnace can be an efficient and effective way to heat a home, as natural gas is often readily available and is typically less expensive than other fuel sources. However, gas furnaces do require regular maintenance to ensure safe and efficient operation. A propane kit can be installed on a natural gas furnace for rural areas without gas service. Parts include: blower motor, draft inducer (vent motor), limit switches, pressure switch, gas valve, control board w/ 3 amp fuse, flame sensor, HSI hot surface ignitor, and blower motor capacitor

Gas Furnace Efficiency Ratings (80%, 90+%)

Gas furnaces with 80% and 90+% efficiency ratings work in a similar manner but differ in how they handle the combustion process and waste gases.

An 80% efficient gas furnace typically has a single-stage burner, which means the gas valve is either fully open or fully closed. When the thermostat signals for heat, the burner ignites and runs at full capacity until the desired temperature is reached. This can result in some energy waste, as the furnace may continue to produce heat even after the home is warm enough.

The exhaust gases produced by the combustion process in an 80% efficient furnace are typically vented out of the home through a metal pipe or chimney. This type of furnace may also have a draft inducer, which helps to ensure that the exhaust gases are properly vented and do not pose a safety hazard.

A 90+% efficient gas furnace, on the other hand, typically has a two-stage burner and a secondary heat exchanger. The two-stage burner can operate at a lower or higher capacity depending on the heating needs of the home, allowing for more precise temperature control and increased energy efficiency. The secondary heat exchanger captures additional heat from the waste gases produced by the combustion process, further increasing efficiency.

The waste gases produced by the combustion process in a 90+% efficient furnace are typically vented out of the home using a plastic pipe or PVC. This is because the furnace extracts so much heat from the waste gases that they are no longer hot enough to require a metal vent pipe or chimney.

Overall, both types of gas furnaces work by burning natural gas to produce heat, which is then circulated throughout the home using a duct system. However, a 90+% efficient furnace typically has additional features that allow it to operate more efficiently and reduce energy waste.