Carrier 59MN7B Installation, Start-Up, Operating And Service And Maintenance Instructions page 21

Return Air Connections
WARNING
!
FIRE HAZARD
A failure to follow this warning could cause personal injury,
death and/or property damage.
Never connect return- -air ducts to the back of the furnace.
Follow instructions below.
The return- -air duct must be connected to bottom, sides (left or
right), or a combination of bottom and side(s) of main furnace
casing. Bypass humidifier may be attached into unused return air
side of the furnace casing. See Fig. 23, 24, 25.
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return- -air opening. Remove this panel when bottom return
air is used. This panel may be used as the bottom closure of an
accessory bottom return air box, or discarded. To remove bottom
closure panel, see Fig. 20 or 21.
Side Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return- -air opening. This panel MUST be in place when
only side return air is used. Where required by code, seal bottom
closure to furnace with tape, mastic or other durable sealing
method.
NOTE: Side return- -air openings can be used in UPFLOW and
some HORIZONTAL configurations. Do not use side return- -air
openings in DOWNFLOW configuration.
25.
5/ 16

(8mm)
3
1 /

4
(44mm)
(8mm)
5 /

16
(44mm) 3/ 4
1
1
(44mm)
Fig. 22 - - Leveling Legs
Leveling Legs (If Desired)
In upflow position with side return inlet(s), leveling legs may be
used. See Fig. 22. Install field- -supplied, 5/16 x 1- -1/2 in. (8 x 38
mm) (max) corrosion- -resistant machine bolts, washers and nuts.
See Fig. 23, 24, and
(8mm)
5/ 16

1 3 /

4
(44mm)
(8mm)
5/ 16


3/ 4

NOTE: Bottom closure must be used when leveling legs are used.
It may be necessary to remove and reinstall bottom flash to install
leveling legs. To remove bottom closure panel, see Fig. 20 or 21.
To install leveling legs:
1. Position furnace on its back. Locate and drill a hole in each
bottom corner of furnace.
2. For each leg, install nut on bolt and then install bolt with
nut in hole. (Install flat washer if desired.)
3. Install another nut on other side of furnace base. (Install flat
washer if desired.)
4. Adjust outside nut to provide desired height, and tighten in-
side nut to secure arrangement.
5. Reinstall bottom closure panel if removed.
Fig. 23 - - Upflow Return Air Configurations and Restrictions
A89014
Fig. 24 - - Downflow Return Air Configurations
21
ANY COMBINATION OF 1, 2, OR 3 PERMITTED.
and Restrictions
A11036
A11037