What a Furnace Plenum Does and Why It’s Important

November 20, 2022
Furnace r in South Charleston, WV

Having a functional and high-performing furnace in your South Charleston, WV home is essential. One large part of keeping your heating system in excellent condition is learning about its components and understanding how to maintain them. Although you probably don’t think much about your furnace’s plenum, this component plays a vital role in hot air distribution. More importantly, if your furnace plenum fails, it can permanently damage your heating equipment. Read on to find out what a plenum is, what it does, and how you can take care of it.

What Is a Furnace Plenum?

The plenum is essentially the backbone of your HVAC system’s air distribution process. Also known as a plenum box, this component handles air as it enters the ductwork of your forced-air heating system. Furnace plenums regulate airflow and humidity as they bring air in, distribute it, and remove it. Indoor air enters this chamber when your heating system is on, and it exits via another plenum before it gets pushed throughout the building.

Different Plenum Types

Forced-air heating systems typically have two plenums: a supply plenum and a return plenum. The supply plenum moves fresh, heated or cooled air into the living environment. It also routes exhaust gases out of the building. The supply plenum box is the first place that warm air enters before it’s pushed through your ductwork and out of your heater vents, grilles, or registers.

Supply plenums are typically located at the lowest points of homes such as in their basements or garages. Supply plenum boxes have louvers for servicing various zones or rooms throughout buildings, and they’re usually made from aluminum, cast iron, or steel.

Return plenums do exactly what their name implies. They send air that’s already been heated and filtered back to furnaces via fans. Return plenums usually have their own air filters that keep heating equipment protected from airborne contaminants. Return plenum boxes draw indoor air in through the HVAC air vents and move it to the return outlets in furnaces.

Benefits Provided By the Furnace Plenum

Your furnace’s plenum streamlines the process of moving heated air both throughout the HVAC system and throughout your home. When installed and working correctly, a furnace plenum allows for quieter HVAC operation. Furnace plenums also optimize airflow so that indoor humidity is decreased and furnace stress is minimized.

It’s also important to note that the furnace plenum offers an additional measure of air filtration. Although the plenum filter is largely intended to protect your HVAC equipment, it still limits the number of particulates being circulated throughout your home. Thus, it allows for a higher indoor air quality (IAQ) overall.

Having a properly functioning furnace plenum can lower your home heating and cooling costs by maintaining the efficiency of your HVAC equipment. It can also extend the lifespan of your furnace by minimizing stress, preventing air pressure issues, and reducing exposure to micro-fine debris. Everyone in the building will breathe a bit easier due to your higher IAQ, and they won’t be bothered with loud humming or rattling sounds when your furnace is on.

How to Avoid Plenum Problems

The first step in making sure that your furnace plenum is working like it should is having it professionally installed. This is a job that should always be handled by a licensed HVAC technician. Mistakes that are made during plenum installation can cause the entire HVAC system to fail. HVAC failure can also occur if the plenum ever becomes blocked or excessively dirty.

The functioning and well-being of the plenum is affected by the condition of your HVAC ductwork. If your HVAC ductwork isn’t installed correctly or if it isn’t regularly maintained, this can cause damage to the furnace plenum and to the furnace itself.

Scheduling professional ductwork cleaning approximately once every three to five years and annual HVAC ductwork inspections should be sufficient for keeping duct-related plenum problems at bay. During your annual furnace service, your HVAC technician will inspect both the supply and return plenum boxes to check for blockages, air leaks, and other problems or signs of distress.

At Mullen Plumbing, Heating and Cooling, we have a longstanding reputation for providing fast, friendly, and reliable HVAC services. We’ve been serving residents of Southwest Charleston, West Virginia and the surrounding areas since 1979. Residents of the Kanawha Valley can turn to us for plumbing, heating, cooling, and water heater service. To find out more about your furnace’s plenum or to schedule furnace maintenance, give us a call!

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