6

REMOVE OLD FILTER AND DISCARD

(Figure 11)

NOTE: This filter may be mounted in the furnace compart-
ment.

CLEAN BLOWER COMPARTMENT

NOTE: The air filter cannot remove dirt from blower and
ducts.

INSTALLATION

The following is a typical installation of the air filter on a
“Highboy” furnace (Figure 7).
1. Place the air filter compartment on the floor. Stand it
upright with the door facing you (Figure 2). If a
horizontal installation is being planned, lay the com-
partment on its side, this will help you to visualize the
relative location of all parts.
2. Unscrew the knob, remove the door (by grasping top
and pulling door away from compartment) and set it
aside. Remove 5” filter. Set in a safe location until the
compartment is installed.
3. Set the compartment next to the furnace (if possible)
to match the opening in the compartment.
If the furnace opening cannot be enlarged, a transi-
tion fitting should be used. (Figure 3).
The compartment can be attached directly (Figure
12), or a starting collar can first be fitted to the furnace
inlet. A butt or slip joint can be used.
Securely attach the compartment to furnace inlet,
using at least two of the mounting holes on each side
of the compartment.
4. Using butt joint, attach duct work (normally an elbow)
to the upstream side of air filter compartment. (Note
the use of the sheet metal turning vanes inside the
elbow to improve air distribution.) (Figure 13)
NOTE: An optional method of attaching duct work to the
air filter cabinet is to modify the compartment (Figure 14)
by bending the tabs outward at a 90° angle and attaching
duct work to tabs.
Transition Fittings
If the air duct does not fit the compartment opening, a
transition fitting should be used. Gradual transitions are
preferred for greatest efficiency. Not more than four
inches per linear foot (approximately 20° angle) should be
allowed (Figure 3).
5. Connect the vertical duct section to the elbow. Wedge
a wood block between floor and elbow for support
(Figure 15).
6. Seal all joints in the return air system downstream
from the air filter with duct tape to prevent dust from
entering the air stream. Tape is usually applied on the
outside of ducts, but may also be applied on the
inside, or both.
INSTALLATION
7. With the air filter compartment installed, re-install 5”
filter and door. (Figure 2)
Figure 11
Air Flow Turning
Vanes

Figure 13

Optional method
(Bend tabs outward at 90˚ angle)
Figure 14