Bryant 830CA Installation, Start--Up, Operating, And Service And Maintenance page 13

Return Air Connections
WARNING
!
FIRE HAZARD
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
Downflow Furnaces
The return- -air duct must be connected to return- -air opening
(bottom inlet) as shown in Fig. 19. DO NOT cut into casing sides
(left or right). Side opening is permitted for only upflow and most
horizontal furnaces. (See Fig. 19) Bypass humidifier connections
should be made at ductwork or coil casing sides exterior to
furnace.
Upflow and Horizontal Furnaces
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 as shown in Fig. 18 and 20. Bypass humidifier may be
attached into unused return air side of the furnace casing. (See
Fig. 18 and 20)
Fig. 17 - - Typical Attic Installation
Fig. 18 - - Upflow Return Air Configurations and Restrictions
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