Gas Furnace Facts - Gas Furnaces are the most used types of heating appliance for our homes and businesses and modern gas furnaces range in efficiency ratings from 79% to 98%. Gas furnaces can either use propane or natural gas for fuel. This largely depends on whether natural gas is available at the location where the appliance is located. Propane is used in rural areas and in urban areas where the natural gas pipeline infrastructure has not been installed. Natural gas is delivered via pipeline while propane is delivered via trucks and pumped into tanks. Tanks are located on the premises where the gas furnace is located. The gas furnace that utilizes the propane for fuel.
Gas Furnace Facts | Fuel for the Furnace
The other differences between propane and natural gas are propane. Propane is heavier than air while natural gas is lighter than air. The BTU rating between propane and natural gas is different with propane offering more BTU’s in comparison. The size of piping used to deliver the two different gases to the appliances. Finally, the pressures of the gases at the point delivery to the appliances. Natural gas produces 1,000 Btu’s of heat per cubic foot burned. Propane produces about 2,500 Btu’s of heat per cubic foot.
Propane or Natural Gas? Gas Furnace Facts
In comparison studies, natural gas is considered the cheaper alternative by far than propane as far as fuel usage and production of heat are concerned. In different comparison studies, it cost nearly 200% more to produce 90,000 BTUs of heat with propane over natural gas. This makes natural gas a more attractive option when considering whether to purchase a natural gas furnace or a propane furnace (really they are the same except when the appliance arrives on site it is converted to propane using a propane conversion kit provided by the manufacturer if the gas furnace is going to be used for a propane application).
The only issue in making the decision between a natural gas furnace or a propane gas furnace is availability. Natural gas is not available in every location. Furthermore, this is the reason why many people have propane gas furnaces for heating systems, cooking, and heating water.
Scientific Definitions | Gas Furnace Facts
Natural gas: A gaseous mixture of hydrocarbon compounds, the primary one being methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium. It is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure under the surface of the Earth over millions of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in the gas.1
Propane (C3H8): A straight-chain saturated (paraffinic) hydrocarbon extracted from natural gas or refinery gas streams, which is gaseous at standard temperature and pressure. It is a colorless gas that boils at a temperature of -44 degrees Fahrenheit. It includes all products designated in ASTM Specification D1835 and Gas Processors Association specifications for commercial (HD-5) propane.2
Safety and Regulation | Gas Furnace Facts
Gas furnaces are regulated for installation purposes. It is necessary for safety reasons to obtain a permit before installing a new gas furnace. Installations of new gas furnaces are typically regulated by the Mechanical Code along with the Fuel Gas Code. Furthermore, it is important to check with local municipalities to ensure all the proper procedures are followed for the proper and safe installation of gas furnaces.
Gas Furnace Facts - Gas Furnace Types
There are many gas furnace types to describe or classify gas furnaces. There are upflow gas furnaces, downflow gas furnaces, lowboy gas furnaces, and horizontal flow gas furnaces.
- Horizontal flow gas furnaces can be either left or right or right to left gas furnaces.
- Another type of gas furnace is a package unit gas furnace which is usually package unit with an air conditioner all in one unit. Everything sans the duct system is all in one gas furnace and air conditioner unit.
- Upflow gas furnaces have the airflow enter the bottom of the unit and supplies hot air out the top of the unit usually into a duct plenum for delivery of hot air throughout the duct system.
- Downflow gas furnaces airflow enters the top of the gas furnace and delivers hot air out the bottom again usually into a ducted plenum for delivering throughout the duct system.
- Lowboy gas furnaces are small gas furnaces designed to be fit in tight areas like closets or other areas with limited space.
The delivery of air throughout the duct system for a horizontal flow gas furnace depends on the way the horizontal gas furnace is installed – left to right or right to left. Package units can be downflow for rooftop gas furnace installations or horizontal flow for installation on the ground just outside the structure where the gas furnace package unit is installed. Additionally, there are also gas fired radiant heaters and gas furnace unit heaters for installation in garages and big open areas where a duct system is not appropriate for installation of a gas furnace.
Gas Furnace Facts - Gas Furnace Components
Every gas furnace needs the following components to work. First, a gas furnace needs a gas line or a fuel source. Depending on the type of gas furnace will depend on the type and size of fuel line used. Lastly, all these considerations are usually made by the installing contractor and comply with the National Fuel Gas Code and local regulations for the sizing and installation including type of materials used for the fuel line. There are many other gas furnace components, some described and some in our other articles.
The next component is the gas valve. The gas valve is like a switch and it opens and closes on a command from a control usually the thermostat. The gas valve delivers gas into a manifold and the manifold delivers gas to the burners.
The burners have an ignition system to ignite the gas. Once the gas ignites it is burned in a heat exchanger. The heat exchanger is designed to keep the combustion processes and gases apart for the heated air. Separate from the airflow stream that is delivered into the home or business. Finally, the typical ignition system for gas furnaces can either be standing pilot or electronic ignition.
Keeping the combustion gases and the airflow stream apart is important. Furthermore, combustion gases contain many noxious gases that are harmful to health including carbon monoxide.
Other gas furnace components include the blower motor and blower assembly, the venting system for properly venting the combustion gases, a forced combustion air blower, and many safety controls to ensure the gas furnace is safely operating.
Gas Furnace Facts - History
The Romans originally invented the furnace around 1200 BC. The Romans used early furnaces for producing metal products. Most likely for tools and ornaments but to fuel their armies with weapons. Consequently, these early furnaces led to central furnaces to keep their homes warm when the weather turned cold.
Gas Furnace Facts | Video
The following video concerns one safety control which is the pressure switch. The pressure switch in a gas furnace monitors the function of the combustion blower. If the combustion blower fails the pressure switch will kill the gas furnace especially the process of combustion. Gas furnace troubleshooting article can be found here.
Gas Furnace Facts
Additional Articles, Resources/Credits and About the Author
He currently works as a consultant on large construction projects assuring that quality control and technical details are met by contractors on the projects. This includes writing reports, test scripts for HVAC systems, automated controls, electrical systems and training operators who will operate and maintain the equipment for the projects. Mr. Ashworth is available for consultation and writing opportunities concerning the mentioned trades specifically specializing in Automation Controls and HVAC, new or retrofit projects. He is also pretty good with websites along with various software platforms. When he is not busy, he is working on his new book - photo to the right.
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