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What Is a Plenum in an HVAC System?

What Is a Plenum in an HVAC System?

December 20th, 2021


In order for your traditional central air conditioner or furnace to function, and bring chilled or heated air into your living space, it needs a series of air ducts to do its job. This ductwork is generally made up of sheet metal, however other rigid materials can be used as well, including fiberglass or insulated plastic. There is one component of this ductwork that has a big job, but its name isn’t very well known–the plenum!

There are actually two types of plenums, which are typically in a rectangular shape. The supply plenum is on one side while the return plenum is typically catty-cornered to it. Read on to learn more!

What is the Supply Plenum?

The supply plenum is an air distribution box. It’s attached directly to the supply outlet of the HVAC equipment–that is, the outlet that releases chilled or heated air into your home. The air ducts that distribute the air into the individual rooms of your living space all connect to this plenum.

Your central AC and furnace systems both have something called a blower fan that forces the air powerfully out of the vents and into the rooms of your living space. There is usually an air filter located here as well.

What is the Return Plenum?

Forced-air heating and cooling system also have returned ductwork that connects to the HVAC equipment through the air-collection box known as a return plenum. As freshly conditioned air or heated air gets blown out of the room supply ducts, “used” air from your living space is sucked into the return ducts.

The air from your home collects in the return plenum, where it’s drawn back into the HVAC equipment through the return inlet for another round of heating and cooling

The return plenum also has an air filter in place. This air filter–typically mistaken by homeowners as a component to protect their indoor air quality–is there to protect the HVAC system itself from dust, dirt, and other debris that could potentially harm its internal components.

The Importance of Your Ductwork

The state of your ductwork and the plenum are vital to the functionality and efficiency of your heating and cooling systems. If the plenum or air ducts are too dirty, it can restrict airflow and force your HVAC system to run longer to try to reach the desired temperatures on your thermostat. If they’re damaged, it can allow up to 30% of your conditioned air to leak out into unoccupied spaces. This is conditioned air you’re otherwise paying for!

If you think your HVAC systems haven’t been working as efficiently as they once did, then damaged or dirty ducts can absolutely be to blame. The best thing to do when and if you suspect this is to give our team a call so we can inspect your entire system, including the ductwork.

If it’s been a handful of years since you’ve had your air ducts cleaned or inspected, now is definitely the time to have them checked out.

For expert air conditioning services and heating services in Canton, look no further than Dayco Systems.
Contact us today!