Filter Arrangement; Air Ducts - International comfort products N8MXL Installation Instructions Manual

2. Rotate bottom filler panel downward to release holding
tabs.
3. Remove bottom closure panel.
4. Reinstall bottom filler panel and screws. Side Return
Air Inlet
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 side return air inlet(s) is used without a bottom
return air inlet.
Not all horizontal furnaces are approved for side return air
connections. (See Figure 20).

FILTER ARRANGEMENT

WARNING
!
CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in personal
injury, or death.
Never operate a furnace without a filter or with filter
access door removed.
There are no provisions for an internal filter rack in these
furnaces.
A field−supplied accessory external filter is required.
Refer to the instructions supplied with the external filter rack
for assembly and installation options.

AIR DUCTS

General Requirements
The duct system should be designed and sized according to
accepted national standards such as those published by: Air
Conditioning Contractors Association (ACCA), Sheet Metal
and Air Conditioning Contractors National Association
(SMACNA) or American Society of Heating, Refrigerating and
Air Conditioning Engineers (ASHRAE) or consult The Air
Systems Design Guidelines reference tables available from
your local distributor. The duct system should be sized to
handle the required system design CFM at the design
external static pressure. The furnace airflow rates are
provided in Table 5 − AIR DELIVERY−CFM (With Filter).
When a furnace is installed so that the supply ducts carry air
circulated by the furnace to areas outside the space
containing the furnace, the return air shall also be handled by
duct(s) sealed to the furnace casing and terminating outside
the space containing the furnace.
Secure ductwork with proper fasteners for type of ductwork
used. Seal supply− and return−duct connections to furnace
with code approved tape or duct sealer.
441 01 1421 01
NOTE:
ductwork and furnace to prevent transmission of vibration.
Ductwork passing through unconditioned space should be
insulated and sealed to enhance system performance. When
air conditioning is used, a vapor barrier is recommended.
Maintain a 1−in. (25 mm) clearance from combustible
materials to supply air ductwork for a distance of 36 in. (914
mm) horizontally from the furnace. See NFPA 90B or local
code for further requirements.
Ductwork Acoustical Treatment
NOTE: Metal duct systems that do not have a 90 degree
elbow and 10 ft. (3 M) of main duct to the first branch take−off
may require internal acoustical lining. As an alternative,
fibrous ductwork may be used if constructed and installed in
accordance with the latest edition of SMACNA construction
standard on fibrous glass ducts. Both acoustical lining and
fibrous ductwork shall comply with NFPA 90B as tested by UL
Standard 181 for Class 1 Rigid air ducts.
Supply Air Connections
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 is installed and
shall be of such a size that the heat exchanger can be
viewed for possible openings using light assistance or a
probe can be inserted for sampling the airstream. The cover
attachment shall prevent leaks.
Upflow and Horizontal Furnaces
Connect supply−air duct to flanges on furnace supply−air
outlet. Bend flange upward to 90_ with wide duct pliers. (See
Figure 14) The supply−air duct must be connected to ONLY
the furnace supply−outlet−air duct flanges or air conditioning
coil casing (when used). DO NOT cut main furnace casing
side to attach supply air duct, humidifier, or other accessories.
All accessories MUST be connected to duct external to
furnace main casing.
NOTE: For horizontal applications, the top−most flange may
be bent past 90 degrees to allow the evaporator coil to hang
on the flange temporarily while the remaining attachment and
sealing of the coil are performed.
Downflow Furnaces
Connect supply−air duct to supply−air outlet on furnace. Bend
flange inward past 90_ with wide duct pliers. (See Figure 14)
The supply−air duct must be connected to ONLY the furnace
supply outlet or air conditioning coil casing (when used).
When installed on combustible material, supply−air duct must
be connected to ONLY the accessory subbase or a 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 to
duct external to furnace casing.
Specifications are subject to change without notice.
Flexible connections should be used between
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