Have you ever had your furnace break down on you? You may pop open the door on the unit, but odds are the inside just looks like a jumble of wires and metal. Unless you are an HVAC technician, you probably don’t know much about your furnace or furnace repairs. But, understanding the basic parts and operation of the unit could make the trouble-shooting process a little easier.
Basic Components of a Gas Central Air Furnace
- Pilot light- The pilot is source of fire that your furnace uses to fire up when your thermostat calls for heat. There are two types of pilot lights: standing pilot and electronic ignition.
- Standing Pilot- This type of pilot light consists of a pilot light assembly and a thermocouple. The pilot light assembly holds a constant flame that should always be lit even when the furnace is not in use. The thermocouple is heated by the flame on the pilot assembly. The thermocouple then generates an electric current that will feed to the gas valve on your furnace. The gas valve is the part of the furnace that regulates the flow of gas into the unit.
- Electronic Ignition- This type of ignition doesn’t have a constant flame. It will only create a flame when the thermostat calls for heat. Instead of a thermocouple, this type of pilot has a flame sensor. The flame sensor will sense the flame created by the pilot and then send a signal to the gas valve to open.
- Inducer Motor- The inducer motor is a small fan-like motor, and it has two main functions. It brings air in from the outdoors to create combustion, and it removes the toxic gases created by the combustion of gas and air. At the beginning of a cycle, the inducer motor will kick on first to get air into the unit to create combustion with the gas released by the gas valve. The combustion is what creates the heat for your home. During the cycle, the inducer continues to run and filter out any of the excess gasses that are created by the furnaces combustion process. This keeps poisonous gasses like carbon monoxide from entering your breathing air.
- Burners- The burners are located in the combustion chamber where the combustion takes place. The gas mixes with the outdoor air and heat is created. The burners will usually glow red when they are hot. They then transfer the heat to the heat exchanger.
- Supply and Return Vents- These are the vents that are located in each room of your home. The supply vent pushes heat into the room. The return vent draws air into it to be taken back to the furnace to be re-heated.
- Heat Exchanger- The heat exchanger is the part of the furnace that heats the air that is blown into the home. There are two sides to the heat exchanger. One side is in contact with the combustion air and gases, and the other side is in contact with the air that circulates through the home. The heat created by the combustion air is transferred through the heat exchanger to heat the air before it is sent through your home. The heat exchanger creates a barrier between you and the harmful gases that are being vented outside by the inducer motor.
- Blower Motor- The blower motor is the big fan that sends the air through the duct work of your home and into each room that receives heat. This fan can either be used only when the furnace is cycling, or it can run all of the time if you set the fan to the “on” position on the thermostat.
There are several other parts in the furnace unit, but these are the main components that are used to heat your home. First the pilot light heats either the thermocouple or flame sensor. The thermocouple/ flame sensor will then send an electric current to the gas valve. The gas valve will open and send gas to the combustion chamber. The gas mixes with the air that is drawn in by the inducer motor, and the burners will fire up. The heat created here will be transferred through the heat exchanger. The air that is being drawn back to the furnace through the return vents will flow through the heat exchanger. As the air passes through the heat exchanger it is warmed and then transferred to the duct work that leads to the supply vents for each room in the home.
This is basically how your furnace creates heat. Now the next time you have a furnace problem, you will have a better idea of what may be wrong. Unfortunately, many of the things that can go wrong with a furnace will still require the help of a certified HVAC specialist. When this happens, Four Seasons Heating and Air Conditioning is available 24 hours a day 365 days a year. Our technicians are NATE certified, and are prepared to work on every make and model. So before you panic, remember Four Seasons is always there to help you get your heat up and running once again.