Components Of Distribution Systems
Distribution systems have a number of important components:
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The
Air Handling Unit is a cabinet that includes or houses the central
furnace, air conditioner, or heat pump and the plenum and blower assembly that
forces air through the ductwork.
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The
Supply Ductwork carries air from the air handler to the rooms in a
house. Typically each room has at least one supply duct and larger rooms may
have several.
-
The
Return Ductwork carries air from the conditioned space back to the air
handler. Most houses have only one or two main return ducts located in a
central area.
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Supply and Return Plenums are boxes made of duct board, metal, drywall
or wood that distribute air to individual ducts or registers.
The
Ductwork is a branching network of round or rectangular tubes generally
constructed of sheet metal, fiberglass board, or a flexible plastic and wire
composite material and located within the walls, floors, and ceilings. The three
most common types of duct material used in home construction are metal,
fiberglass duct board, and flex-duct.
Flex-duct is installed between the register and plenum box, or plenum box
and air handler, usually in a single, continuous piece. While flex-duct has
fewer seams, the inner lining and outer insulated covering can tear or be
pinched closed. Also longer flex-duct runs can restrict the flow of air; proper
design and installation is very important.
Both
metal and fiberglass duct board are rigid and installed in pieces.
Fiberglass duct board, like flex-duct, is made of an insulation material. Ducts
are built of sections of the duct board. The seams in the duct board should be
carefully sealed with mastic or high quality duct tape.
Rectangular metal duct , especially the kind used for plenums and larger
trunk runs, is often insulated on the inside with fiberglass duct liner. If it's
not insulated on the inside, metal ducts should be insulated on the outside
using a fiberglass batt with an attached metal foil vapor retarder. The
insulation should be at least two inches thick, and the vapor barrier installed
on the outside of the insulation facing away from the duct.
The seams in the insulation are usually stapled together around the duct and
then taped. All of the seams should be sealed before insulation is installed.
All return and supply ducts located outside the conditioned space, in attics,
crawlspaces, or basements, for example, should be sealed and insulated.
Ductwork Joints join pieces of ductwork.
Elbows are manufactured pieces of duct used for turns.
Boots connect ductwork to registers.
Registers and
Grilles are the coverings for duct openings into the conditioned space.
