How Large Are Plenums Required For HVAC Systems?

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How Large Are Plenums Required For HVAC Systems?

How big is your plenum box? When it comes to plenums does size matter? What the heck is a plenum box? Okay, admittedly Merts Heating & Air Conditioning doesn’t get a lot of plenum questions from our Illinois and Northwest Indiana clients, but it’s still a very important part of your HVAC systems, which is why you should know more about them.


Most systems will have two plenum boxes, one on the supply side and one on the return air side. They serve as the distribution point for the air that circulates throughout the home. The conditioned air passes from the air handler through the plenum then into the ductwork. The air from the return vents passes through the plenum box back into the air handler. If you’re still trying to visualize these parts on your system, the two boxes are always separated by your HVAC filter.


The filter location allows the air to be cleaned as it passes from the return side plenum box into the air handler. After the air is conditioned, heated or cooled, it passes from the air handler into the supply side plenum box. The entire process is dependent on correct airflow throughout the system.


The only thing you really need to know is the plenum boxes must be correctly sized or your HVAC systems won’t heat and cool efficiently.  It’s another reason why it’s important to hire only qualified technicians to do HVAC work in your Steger, IL or Crown Point, IN house. It’s a task that requires specialized training to understand the complicated formula used to determine proper sizing. It needs to take many factors into account including duct size and how far the air has to travel during its journey through the house.


The plenum boxes are just another example of how important the design and installation phases are in assuring HVAC systems keep homes comfortable year-round. If a system is installed with the wrong size plenums and/or ducts, the resulting problems are difficult and expensive to repair. It’s why you should depend on Merts Heating & Air Conditioning which has been serving Illinois and Northwest Indiana since 1952. Learn more about the services we offer by liking us on Facebook and following us on Twitter.