Page 9
Pub. No. 41-5010-20
Installation Instructions
Minimum return air “entering temperature” for the fur-
nace is 50° F.
Where there is no complete return duct system, the return
connection must be run full size from the furnace to a location
outside the utility room, basement, attic, or crawl space.
Do Not install return air through the back of the furnace
cabinet.
Do Not install return air through the side of the furnace
cabinet on horizontal applications.
RETURN AIR DUCT CONNECTION
All return air duct systems should provide for installation of
return air filters.
1. Set the furnace in place.
2. For side return installations on upflow models, remove the
insulation around the opening in the blower compartment.
3. The side panels on upflow furnaces include locating notches
which may be used as guides for cutting an opening for return air.
Refer to Figure 12 and the Outline Drawing on page 4 for duct
connection dimensions for various furnaces.
4. If a 3/4" flange is to be used for attaching the air inlet duct,
add to cut where indicated by solid lines in Figure 12. Cut corners
diagonally and bend outward to form flange.
* SEE OUTLINE DRAWING
LOCATING
NOTCHES
PROVIDED
FOR SIDE
RETURN
CUTOUT
*
*
*
*
CUT OUT
FOR
SIDE
FILTER
FRONT
of Furnace
FIGURE 12
RETURN AIR FILTER
Filters are field supplied for these furnaces. These furnaces
require high velocity type air filters which may be located within
the furnace blower compartment for UPFLOW furnaces in either
a BOTTOM or SIDE (left side or right side) return air inlet. See
Figure 14. Some filters may need to be trimmed for side or bottom
filter use.
NOTE:
On upflow 5 ton airflow models, if the airflow requirement
exceeds 1800 CFM, these models will require return air open-
ings and filters on both sides; OR 1 side and the bottom; OR
just the bottom.
Downflow furnace filters must be located outside the furnace
cabinet. Typical installations are shown on page 10 in Figure 13.
Tables 5 and 6 on page 10, provide information for installation of
the filter retaining brackets shipped with downflow furnaces.
FILTER RETAINER BRACKETS FOR
UPFLOW FURNACES
If locating filter inside the furnace blower compartment is de-
sired, it is necessary to install the 2 filter retainer brackets. Filter
retainer brackets are shipped with the furnace in a plastic bag
attached to the control platform. Follow the installation instruc-
tions included inside the plastic bag with the filter retainer
brackets. (See Figure 14 “Typical Side Return Filter”).
5. If flanges are not required, and a filter frame is installed, cut
along knockout guidelines.
6. Upflow furnaces: filter retainer brackets are factory supplied
(See Figure 14). Use the filter retainer brackets on either side or
on bottom if filter is to be used within the furnace cabinet.
NOTE:
On upflow 5 ton airflow models, if the airflow requirement
exceeds 1800 CFM, these models will require return air open-
ings and filters on both sides; OR 1 side and the bottom; OR
just the bottom.
7. Connect duct work to furnace. See Outline Drawing for
supply and return duct size and location. Flexible duct connectors
are recommended to connect both supply and return air ducts to
the furnace. If only the front of the furnace is accessible, it is
recommended that both supply and return air plenums are
removable.
8. When replacing a furnace, old duct work should be cleaned
out. Thin cloths should be placed over the registers and the
furnace fan should be run for 10 minutes. Don’t forget to remove
the cloths before you start the furnace.
TABLE 4
REQUIRED FILTER SIZES - UPFLOW
CABINET
WIDTH
QTY
(See Note)
CABINET
BOTTOM FILTER
CABINET
SIDE FILTER
14-1/2"
1
14" X 25" X 1"
17" X 25" X 1"
17-1/2"
1
17" X 25" X 1"
17" X 25" X 1"
21"
1
20" X 25" X 1"
17" X 25" X 1"
24-1/2"
1
24" X 25" X 1"
17" X 25" X 1"
*
NOTE -
On upflow 5 ton airflow models, if the airflow requirement
exceeds 1800 CFM, these models will require return air openings
and filters on both sides; OR 1 side and the bottom; OR just the
bottom.
REQUIRED FILTERS - DOWNFLOW
CABINET WIDTH
FILTER QUANTITY & SIZE
14-1/2"
2 - 14" X 20" X 1"
17-1/2"
2 - 16" X 20" X 1"
21"
2 - 16" X 20" X 1"
24-1/2"
2 - 16" X 20" X 1"