-- 25 --
supply/outlet or air conditioning coil casing (when used), when
installed on non-combustible material. When installed on
combustible material, supply-air duct attachment must ONLY be
connected to an accessory sub base or factory approved air
conditioning coil casing. DO NOT cut main furnace casing to
attach supply side air duct, humidifier, or other accessories. All
accessories MUST be connected external to furnace main casing.
Supply air opening duct flanges must be modified per Fig. 24.
Horizontal Furnaces
Connect supply-air duct to supply air opening on furnace. The
supply-air duct attachment must ONLY be connected to furnace
supply/outlet or air conditioning coil casing (when used). DO
NOT cut main furnace casing to attach supply side air duct,
humidifier, or other accessories. All accessories MUST be
connected external to furnace main casing.
RETURN AIR CONNECTIONS
The furnace and its return air system shall be designed and
installed so that negative pressure created by the air circulating
fan cannot affect another appliance’s combustion air supply or act
to mix products of combustion with circulating air and the air
circulating fan of the furnace, if installed in an enclosure
communicating with another fuel-burning appliance not of the
direct-vent type, shall be operable only when any door or panel
covering an opening in the furnace fan compartment or in return
air plenum on ducts is in the closed position.
Table 4 – Filter Information
AIR FILTER LOCATED IN BLOWER COMPARTMENT
FURNACE
CASING
WIDTH
IN (mm)
FILTER SIZE --- IN (mm)
FILTER
TYPE
Side Return†*
Bottom Return*
17–1/2
(445)
(1) 16 X 25 X 3/4
(406 X 635 X 19)
(1) 16 X 25 X 3/4
(406 X 635 X 19)
Washable
21 (533)
(1) 16 X 25 X 3/4
(406 X 635 X 19)
1) 20 X 25 X 3/4
(508 X 635 X 19)
Washable
24–1/2
(622)
(1 or 2)16 X 25 X 3/4
(406 X 635 X 19)
(1) 24 X 25 X 3/4
(610 X 635 X 19)
Washable
*Alternate sizes and additional filters can be ordered from your distributor or
dealer.
†
Upflow only. Alternate sizes and additional filters may be ordered from
your dealer.
FIRE HAZARD
A failure to follow this warning could result in fire, personal
injury, or death.
Never connect return-air ducts to the back of the furnace.
Return-air duct connections on furnace side(s) permitted in
upflow applications only.
!
WARNING
Upflow Furnaces
The return-air duct must be connected to end, sides (left or right),
or a combination of end and side(s) of main furnace casing as
shown in Fig. 2. Bypass humidifier may be attached into unused
side return air portion of the furnace casing. DO NOT connect
any portion of return-air duct to back of furnace casing.
Downflow and Horizontal Furnaces
The return-air duct must be connected to end inlet opening
provided as shown in Fig. 2. DO NOT cut into casing sides or
back to attach any portion of return-air duct. Bypass humidifier
connections should be made at ductwork or coil casing sides
exterior to furnace.
Step 5 -- Filter Arrangement
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in fire, personal
injury, or death.
Never operate a unit without a filter or with filter access
door removed.
!
WARNING
Determine location for filter and relocate filter retaining wire if
necessary. See Table 4 to determine correct filter size for desired
filter location. Table 4 indicates filter size and location for this
furnace. See Fig. 2 for location and size of bottom and side
return-air openings.
CUT HAZARD
Failure to follow this caution may result in minor
personal injury.
Use care when cutting support rods in filters to protect
against flying pieces and sharp rod ends. Wear safety glasses,
gloves, and appropriate protective clothing.
CAUTION
!
A08604
Fig. 26 -- Filter Installed for Side Inlet
UNIT MAY NOT OPERATE
Failure to follow this caution may result in intermittent
unit operation.
For airflow requirements above 1800 CFM, see Air Delivery
table in Product Data literature for specific use of single side
inlets. The use of both side inlets, a combination of 1 side
and the bottom, or the bottom only will ensure adequate
return air openings for airflow requirements above
1800 CFM.
CAUTION
!
NOTE
:
Side return-air openings can ONLY be used in
UPFLOW configurations. Install filter(s) as shown in Fig. 26.
Bottom return-air opening may be used with all 4 orientations.
Filter may need to be cut to fit some furnace widths. Install filter
as shown in Fig. 27.
58MCB