Gas furnaces are a class of HVAC equipment that rely on gasoline to warm an entire facility. These heating systems, that typically use LPG or natural gas, have been developed to become surprisingly efficient over the years. They operate by using a careful distribution of ductwork and a system of coils known as a heat exchanger to warm a building evenly.


These are large systems that are fixed permanently in a building which is why an HVAC professional must first take into account several calculations. These include:

  • Inspecting a building’s insulation.
  • The placement of the furnace based on the space available.
  • Taking care of gas and electrical lines.
  • The removal of previous HVAC equipment in some cases.
  • That the ductwork is suited to the furnace.

The installation process of gas furnaces is rather invasive which is why it is important that every calculation is taken accurately beforehand and that the installation team is made aware of the thermal specifications of a building so that a suitably powered unit is selected.

How Gas Furnaces Function

To understand how they operate, it is important to understand how the components work in concert to control the temperature of a building.

  • The Thermostat: The thermostat delivers an electrical signal to the furnace which concurrently activates it.
  • Burners: After receiving a signal from the thermostat, the burner activates and warms the heat exchanger using high intensity flames.
  • The Heat Exchanger: The Heat Exchanger is a coil of metal loops that warm the air upon being heated.
  • The Blower Motors: The blowers then blow the warm air through to the ventilation system and ductwork in the building.
  • The Ventilation System: The ductwork and ventilation system of the house circulates the warm air evenly across the facility.


A gas furnace’s efficiency is measured using the Annual Fuel Utilisation Efficiency (AFUE) ratio. This takes into account the heat that a gas furnace produces in a year compared to how much was spent on gas to operate the system. When it operates, it needs to release Carbon Dioxide from its vents and in the process, releases a certain amount of heat. Modern furnaces have streamlined this process to a large degree compared to furnaces in the past. If a system has an AFUE of 85, then that means that it turned 85% of the fuel it was provided into usable heat. Likewise, a furnace with an AFUE of 95 translates into 95% of the fuel it used into useful heat. High efficiency furnaces have an AFUE of over 90, however, some systems offer an AFUE of up to 98.5%. Being cautious about the efficiency of the unit can make operating one significantly cost effective in the long run.

AFUE ratings can, however, get confusing in certain cases and do not necessarily translate to reduced costs. A gas furnace with a lower AFUE rating but that has other components more suitable for a building such as a larger number of blower motors. Other factors such as the insulation of a building can greatly impact how much it costs to run even a highly efficient gas furnace. Although a high efficiency system seems like a better idea in the long run, modifications may need to be made to a building that are significant cost drivers such as replacing the current ventilation system.

Problems with Gas Furnaces

Identifying problems can be problematic given how deeply integrated the system is to the building. However, below are some of the most common problems experienced with gas furnaces.

  • The filters are blocked: If the filters are not cleaned regularly enough then they can get full of dirt and cease to function. This also damages how efficient the heating system is and how well it performs.
  • Damaged Heat Exchanger: The heat exchanger is a highly important component of a furnace and damages to it can be detrimental. Damages to the heat exchanger occur when the filters are not replaced in time.
  • No Air: A lack of air coming through the vents is usually caused when the blower motor is either damaged or clogged with dust.
  • Malfunctioning Thermostat: This can be caused by electrical issues such as damaged connections which can harm the battery of the thermostat. To diagnose this issue in the first place, check if your fan keeps running on automatic and performs at various settings.

Maintenance and Replacement

The best way to ensure that a system is running at its full potential, is the adoption of a maintenance routine. Since gas furnaces are dangerous pieces of equipment given the gas, electrical connections and the sheer amount of heat, it is highly recommended that an HVAC professional should handle most of the maintenance. Here is a short list of the maintenance that a these units require:

  • Cleaning and swapping the filters out.
  • Cleaning the blower motors and the fans.
  • Perform Indoor Carbon Monoxide tests.
  • Removing dust and debris from the vents and air intake grills.
  • Swapping the filters out.
  • Carbon monoxide tests.
  • Having an HVAC professional check the furnace regularly and calculate how efficient it is.

At some point in time, however, a gas furnace will run its course and a replacement will be required which is why it is safer in some instances to replace a gas furnace. To diagnose whether or not you need to replace your whole system, there are a few signs that users should be aware of.

  • Peculiar Noises: A rattling, screeching, rattling or humming noise coming from the furnace could be a sign that the blower motor is damaged or other components inside of your furnace such as the burners that heat up the heat exchanger. If these parts are damaged it may be more economical to replace a gas furnace than to have it repaired.
  • Frequent Repairs and High Bills: If a gas furnace is not as efficient as it used to be and is resulting in higher bills than before then it may be time to replace the unit as a whole. Frequent repairs are also a sign that it may be time to replace a furnace as inner components may be damaged that can possibly be more expensive to replace in comparison to the purchase of a new system altogether.

Order a Gas Furnace Online

The procurement of a gas furnace, installation and maintenance that might require expert assistance. For more information about gas furnaces or to speak to an HVAC expert, contact ProServices Supply today. We are a leading Facility Maintenance Solutions provider based out of Atlanta, GA, and have our services available across the US. You can order a gas furnace online through our website or call us at (877)-776-8228 to speak to an expert today for more information.

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