12
18-CD20D1-18
Installer’s Guide
RETURN AIR FILTERS FOR UPFLOW FURNACE
IN HORIZONTAL CONFIGURATION
When the Upflow Furnace is installed in the horizontal
configuration, the return air filters must be installed exterior
to the cabinet. Remote filter grilles may be used for home-
owner convenience or the filters may be installed in the duct
work upstream of the furnace. See Figure 21.
BLOWER DOOR/HINGE REMOVAL
If clearance or other problems create a problem in using the
tilting door, the blower door hinge may be removed without
creating any problems with the seal of the furnace. To
remove the blower door, tilt the door forward 2 to 3 inches
and pull up. To remove the tilt feature, simply remove the
lower hinge as shown in Figure 22. The bottom of the blower
door will catch in the bottom of the furnace front channel for
door replacement.
REAR
SIDE
CUT
-OUT
ALTERNATE FILTER
CLIPS LOCATION
d
Door Hinge Removed
Airf low
s
ALTERNATE UPFLOW
FILTER CLIP / BRACKET INSTALLATION
1. Determine the location to be used. The furnace cabinet
has dimples for location of the alternate furnace clips
(
Side return only
). Pre-drill clearance holes with a
3/16" drill. Bottom return holes are pre-drilled.
2. Install the clips in front and rear of the desired location
using the screws provided. The filter clip with the leaf
spring mounts in the rear of the cabinet.
UNIT
SIZE
RETURN AIR
BOTTOM
SIDE
17-1/2"
DO NOT CUT
DO NOT CUT
21"
DO NOT CUT CUT ON LINE
24-1/2"
DO NOT CUT CUT ON LINE
INSTALLING THE FILTER
The filter may need to be cut to fit the unit depending on the
location of the return air filter.
A score line and the words “CUT HERE” are located on the
end of the filter. If your application requires cutting the
filter, do so as indicted by the score mark.
Airflow
Airflow
f
TYPICAL DOWNFLOW FURNACE
RETURN AIR FILTER INSTALLATIONS
Two filters are factory supplied for each downflow furnace.
These furnaces require high velocity type air filters. Down-
flow furnace filters must be located outside the furnace
cabinet. Typical installations are shown in Figure 24. Tables
5 and 6 provide information for installation of the filter
retaining brackets shipped with downflow furnaces.
