What is supply plenum?

The supply plenum is a box that is connected to your HVAC system's supply outlet. Your AC system's blower sends cool or warm air into the supply plenum, which is then distributed throughout your home through your ductwork.

What is the purpose of a plenum?

Plenum boxes are usually situated on either side of the fan or heat exchanger and have the important function of bringing in, distributing, and removing air. They are the air's first stop after being heated or cooled and its last stop before going back into your AC, heat pump, or furnace.

Do you need a supply plenum?

A: In modern forced-air HVAC systems, you must have a plenum installed.

What is a supply and return plenum?

A supply plenum works by taking in the new cool or warm air from the heater or air conditioning system and, in turn, distribute it throughout the building using the HVAC's ductwork. A return plenum takes in that used air and, using the ductwork, sends it back to the core HVAC system.

Where is the supply plenum?

A supply plenum is an enclosed compartment that's located just after your heat exchanger if you follow the flow of air through your furnace (see below). When your air handler blows air over your system's heat exchanger, that warm air is directed into the supply plenum.

The Role of the AC Plenum

What does plenum mean in HVAC?

In building construction, a plenum (pronounced PLEH-nuhm, from Latin meaning full) is a separate space provided for air circulation for heating, ventilation, and air-conditioning (sometimes referred to as HVAC) and typically provided in the space between the structural ceiling and a drop-down ceiling.

Why do we use plenum in HVAC?

Plenum boxes are used to distribute heated or cooled air throughout your home's interior. After producing heated or cooled air, the HVAC system must move that air through the ductwork. Plenum boxes take in this air so that it can be pumped into the ductwork and, therefore, distributed throughout your home's interior.

How does a plenum differ from a duct?

A plenum is an air-distribution box attached directly to the supply outlet of the HVAC equipment that heats or cools the air to make the house comfortable. The ductwork that distributes the heated or cooled air to individual rooms of the house connects to the plenum.

How long should a supply plenum be?

Single plenums should not exceed 24 ft in length. Double plenums should not exceed 48 ft in total length.

How do I insulate my supply plenum?

After sealing ductwork, use spray foam or wrap a flexible insulation product (e.g., reflective insulation, fiberglass batts) around metal supply ducts, plenums and trunks in basements and crawlspaces. Do not use flexible ductwork in crawlspaces, as it can be an entry point into the home for vermin.

Is an open ceiling considered a plenum?

Plenum spaces are the open spaces above the ceiling or below the floor that are used for air circulation. Technically, any ductwork is considered a plenum space too.

Should an AC plenum be insulated?

Supply and return air ducts and plenums shall be insulated with a minimum of R-6 insulation where located in unconditioned spaces and where located outside the building with a minimum of R-8 insulation in Climate Zones 1 through 4 and a minimum of R-12 insulation in Climate Zones 5 through 8.

What's the difference between plenum and non plenum?

Thus, fire and building safety codes mandate plenum-rated cables be used in plenum spaces and air ducts. They can also be used in non-plenum areas. Non-Plenum cables, on the other hand, are much cheaper and not as fire-resistant. When burned, they release toxic fumes such as hydrochloric acid and dioxin.

How do you attach duct plenum to air handler?

It's typically about 4" by 6" by 10-12' long - it's about 24 gauge. Buy a section of it and cut off some 6-8" pieces to use them as the corners of the air handler opening. Screw them securely onto each corner of the air handler flange and then slide the ductboard plenum over them.

What is the duct?

any tube, canal, pipe, or conduit by which a fluid, air, or other substance is conducted or conveyed. Anatomy, Zoology. a tube, canal, or vessel conveying a body fluid, especially a glandular secretion or excretion.

What is a furnace bonnet?

The bonnet is the actual btu's you'll get after the loss from the flue and ambient loss etc. I find it puzzling that furnace has a 80% difference. When calculating a heat loss load in a home, it's best to use this bonnet to decide the size heater needed.

Can I use foam board for ductwork?

You can build ducts from rigid foam board to serve as the distribution system to circulate heated or cooled air in your house. As with all duct systems, it is essential that one built from rigid foam board is correctly designed so that the temperature is comfortable and consistent throughout the residence.

Can you use flex duct return air?

Yes, you can use flex ducts for your return air. However, to maximize its usefulness, it needs to conform to technical specifications such as its insulation rating, pressure checks, dust filters, duct sizing and placement, and lastly, the installation requirements.

What is the return side of the air handler?

Stand in front of the furnace and look at the vents. The upper duct work on top of the furnace attaches to the heat exchanger. This is the hot air side of the furnace. The duct work that attaches to the furnace at ground level is the return air side of the furnace.

How hot does a furnace plenum get?

The temperature rise from return to supply is usually between 40 and 70 degrees. A reasonable operating temperature would be 140F.