Instructions / Assembly

Heating and Cooling Essentials
Adjustable Elbow
90°
45°
Figure 28-26. Adjustable elbows are convenient for making
all types of turns. They are available in all round duct sizes.
flat, use a utility knife, to make a series of slices about
every two inches along its edge. When the material is
wrapped around the round duct, the tabs will fan out
and lie flat against the rectangular duct, Figure 28-27.
28.10 Extended Plenum System #
Begin with the takeoff fitting in the plenum, and
work outward. When a branch pipe comes off the top
Figure 28-27. After securing the collar with sheet metal
screws, seal the collar with membrane and mastic. This
prevents leaks due to vibration. Cutting slits in the
membrane will help it lie flat.
of the extended plenum, install the starting collar before
assembling the rectangulai" duct. Side staiting collars or
takeoffs can be installed in the extended plenum after
the run is completed. See Figure 28-28.
Support the duct at intervals with hangers or straps.
Be .sure to keep ducts at least one inch from joists and
other combustible materials. Close the end with an end
cap. After completing the extended plenum with
starting collars or takeoff fittings attached, install
branch runs to connect with outlets, insulate all supply
ducts and pipes that are located in unheated areas.
28.10.1 Working with Rectangular Duct
Most rectangular duct is made of 28-gauge galva-
nized sheet metal in 4' lengths. Each duct length is
made up of two half sections, as shown in Figure 28-29.
Branch piping
Plenum
Figure 28-28. An extended plenum system uses side takeoff fittings to connect branch lines. A centrally located furnace may
have two extended plenums, one on each side.