area. It is often advisable to route the return air ducts under the Filters are not supplied with these furnaces, butcan be purchased
floor or through the attic, from your distributor.
•Refer to furnace Technical Support Manual (Blower Data)
for air flow information.
• Size ductwork to handle airflow for heating (and air condition-
ing if so equipped).
Duct Installation Requirements
When a furnace isinstalled so that supply ducts carry air cir-
culated by the furnace to areas outside of the space contain-
ing the furnace, the return air shall also be handled byduct(s)
sealed to the furnace casing and terminating outside the
space containing the furnace.
CARBON MONOXIDE POISONING HAZARD.

Failure to follow safety warning exactly could

result in death, personal injury, and/or component

damage.

Install cooling coil on furnace discharge. Cool air

passing over heat exchanger could cause conden-

sate to form resulting in heat exchanger failure.

• When the furnace is used with acooling unit, the furnace shall
be installed parallel with or on the upstream side of the cooling
unit to avoid condensation in the heating element.
With a parallel flowarrangement, the da topers or other means
used to control flow of air shall be adequate to prevent chilled
air from entering the furnace. Chilled airgoing through the fur-
nace could cause condensation and shorten furnace life.
Dampers (purchased locally) can be either automatic or
manual. Manually or automatically operated dampers MUST
be equipped with a means to prevent furnace and air condi-
tioning operation, unless damper isin the full heat or cool posi-
tion.
•Installation of locking-type dampers is recommended in all
branches, orin individual ducts to balance system's air flows.
• Non-combustible, flexible duct connectors are recom-
mended for return and supply connections to furnace.
• Ifair return grille is located close to the fan inlet, install at least
one 90° air turn between fan and inlet grille to reduce noise.
• Ductwork installed inattic or exposed tooutside temperatures
requires a minimum of 2" of insulation with outdoor type vapor
barrier.
• Ductwork installed in an indoor unconditioned space requires
a minimum of1" of insulation with indoor type vapor barrier.

InspectionPanel on some models

For a furnace not equipped with a cooling coil, the outlet duct shall
be provided with a removable access panel. This opening shall be
accessible when the furnace isinstalled and shall be of such a size
that the heat exchanger can be viewed forpossible openings using
light assistance or a probe can be inserted for sampling the air
stream. This access cover shall be attached in such a manner as
to prevent airleaks.
Filters
A filter MUST be used.
441 01 2613 02
See Table 4 for required high-velocity filter sizes.
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Cabinet
Width
151/2
191/2
223/4

High-Velocity Air Filter Sizes (max.600FPM)

Internal Filter External Filter Rack
Bottom Bottom Side+
14X25 14X25 14X25 or 16X25
16X25" 16X25" 16X25"
20X25" 20X25" 16X25"
Greater than 1600 CFM requires both (left and right) side return filter
racks in upflow position.
+Side return airduct(s) isnot permitted with horizontal ordownflow furnace
installation,
Use either filter type:
• Washable, high-velocity filters are based on a maximum air
flow rating of600 FPM.
• Disposable, low velocity filters are based on a maximum air
flow of 300 FPM when used with external filter grille.

RISK OF REDUCED FURNACE LIFE

Failure to follow these Caution may result in

premature furnace component failure.

Use of excessively dirty and/or restrictive air filters

may increase furnace operating temperatures and

shorten the life of the furnace.

Filters specified for the furnace are rated at a maximum

of 600 FPM air velocity and sized for the furnace's

airflow rate. Replacement filters must be of equivalent

type, size, and rating except as described below.

Disposable, low-velocity filters may be used to replace

washable, high-velocity filters, providing they are sized

for 300 FPM or less.

I
• The furnaces with 1600 or less CFM rating use a 16" x 25"
high-velocity filter. On these models the filter may be
mounted internally for bottom return or afilter and rack may
be mounted externally for bottom return.
• The furnaces with greater than 1600 CFM require that both
(left and right) side returns are used. Two side return filters
and racks are required. Filter racks must be mounted exter-
nally. See Figure 24.
• If return air must be on one side only, an optional 20" x 25"
filter standoff rack kit can be used. (See Figure 22.) For bot-
tom return, an internal filter can beused or a filter rack kitcan
be mounted externally.
• See pages 40 &46, CirculatorAirBIowerData for additional
data.
NOTE: The 20" x25" standoff side filter rack gives more filter area
but does not provide more air. See Figure 22. To achieve 2000
CFM 2 side returns are still needed. See Figure 24.
NOTE: Disposable low-velocity filters may be replaced with
washable, high-velocity filters. Washable, high-velocity filters can
be replaced ONLY with same type and size filter unless low-veloc-
ity filters meet the minimum size areas for 300 FPM or less.