Figure 4. Return Air Box
Position the supply duct collar, if supplied, so the
edge of the unit opening ﬁ ts between the ﬂ ange
and the bead. Overlap the collar ends keeping the
small screw holes underneath. Align the holes in
the crimped area and install one screw.
Note: It may be necessary to loosen the four
screws that hold the transition duct in order to
install the supply ﬁ tting. Re-tighten when instal-
lation is complete.
Tap collar as necessary to ensure engagement
with unit opening and install second screw.
Tighten ﬁ rst screw. Rotate collar clockwise so
joint is near three o'clock position.
The 12" return duct is installed in the same
manner as the supply duct. If the duct has a 14"
return, follow these instructions.
Align the slots with the holes in the collar and
install two screws. Position the collar over the
opening and align the four notches in the collar
with the four dimples in the panel. Using self-
drilling screws (10-16x.5) attach the collar to the
rear panel. On some models a 14" duct collar is
provided for the return duct.
5. LOCATING AND INSTALLING THE
RETURN AIR ASSEMBLY
To avoid complications, locate and install the
return air assembly ﬁ rst. The return air box with
grille and ﬁ lter (Figure 4) should not be located
in heavy trafﬁ c areas like hallways or center of
rooms. A good spot is in a corner or under a table,
if a minimum two inch clearance is available.
If desired, the return opening can be located
inside a closet with louvered doors that have
an open area equal to or greater than the 12" x
20" grille furnished. The return air grille can be
placed in the wall of a closet and the air ducted
into the ﬁ lter box through a boxed-in area at the
closet ﬂ oor level. Make sure the ﬁ lter is readily
After determining the location of the return air
opening, start the installation from under the
home by cutting a small hole in the ﬁ ber under-
board to determine how the ﬂ oor joist location
will affect cutting the opening needed for the box.
Floor joists generally are located on 16" centers,
leaving 14-3/8" between joists. After measuring
the return air box (approximately 12-1/4" x 20-
1/4"), cut the hole through the ﬂ oor so that the
box will ﬁ t between the ﬂ oor joists. Care should
be taken when cutting through carpeting to avoid
snags. In most installations it will be necessary to
cut a similar hole in the ﬁ berboard directly under
the hole in the ﬂ oor. However, if the ﬂ oor is more
than ten inches deep, it will only be necessary
to cut a hole for the collar on the return air box
or for the insulated duct.
Set the box into the opening and fasten with
screws or nails. Put the ﬁ lter and return air
grille in place.
6. LOCATING AND INSTALLING THE
When locating the supply damper(s), carefully
check ﬂ oor joists and frame members that could
interfere with the installation of the damper
or ﬂ exible duct. Ideally, the damper should be
located in the bottom of the main duct, forward
of center of the home, at least three feet from
the nearest register. The round supply opening
in the slanted side of the damper should face
the side of the home where the heat pump is
located. To locate the center of the heat duct,
ﬁ rst cut a small hole in the ﬁ berboard below the
duct at the desired location. After locating the
duct center, cut a hole approximately 3/4" larger
than the damper opening in the ﬁ berboard. Cut
a 9-1/8" x 13-1/8" hole in the duct and bend over
AUTOMATIC DAMPER IS CLOSED
Figure 5. Supply Damper
WHEN HEAT PUMP IS OFF