Air Ducts - International comfort products N8MSN Installation Instructions Manual

FURNACE
CASING
WIDTH
Upflow Applications on Combustible or Noncombustible Flooring
Downflow Applications on Noncombustible Flooring
14–3/16
(360) Downflow Applications on Combustible Flooring
Downflow Applications on Combustible Flooring with Coil END4X,
ENW4X or Coil Casing NAEA (subbase not required)
Upflow Applications on Combustible or Noncombustible Flooring
Downflow Applications on Noncombustible Flooring
17–1/2
(445) Downflow Applications on Combustible Flooring
Downflow Applications on Combustible Flooring with Coil END4X,
ENW4X or Coil Casing NAEA (subbase not required)
Upflow Applications on Combustible or Noncombustible Flooring
Downflow Applications on Noncombustible Flooring
21
(533) Downflow Applications on Combustible Flooring
Downflow Applications on Combustible Flooring with Coil END4X,
ENW4X or Coil Casing NAEA (subbase not required)
Upflow Applications on Combustible or Noncombustible Flooring
Downflow Applications on Noncombustible Flooring
24−1/2
(622) Downflow Applications on Combustible flooring
Downflow Applications on Combustible Flooring with Coil END4X,
ENW4X or Coil Casing NAEA (subbase not required)

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.
NOTE: Flexible connections should be used between
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.
441 01 1402 02
Table 4—Opening Dimensions − In. (mm)
APPLICATION
(subbase not required)
(subbase not required)
(subbase required)
(subbase not required)
(subbase not required)
(subbase required)
(subbase not required)
(subbase not required)
(subbase required)
(subbase not required)
(subbase not required)
(subbase required)
PLENUM OPENING
A
12−11/16 21−5/8
(322)
12−9/16
(319)
11−13/16
(284)
12−5/16
(319)
16 21−5/8
(406)
15−7/8
(403)
15−1/8
(384)
15−1/2
(394)
19−1/2 21−5/8
(495)
19−3/8
(492)
18−5/8
(473)
19
(483)
23 21−1/8
(584)
22−7/8
(581)
22−1/8
(562)
22−1/2
(572)
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 air stream. The cover
attachment shall prevent leaks.
FLOOR OPENING
B C
13−5/16 22−1/4
(549) (338) (565)
19 13−3/16 19−5/8
(483) (335) (498)
19 13−7/16 20−5/8
(483) (341) (600)
19 13−5/16
(483) (338) (508)
16−5/8 22−1/4
(549) (422) (565)
19 16−1/2 19−5/8
(483) (419) (498)
19 16−3/4 20−5/8
(483) (425) (600)
19 16−1/2
(483) (419) (508)
20−1/8 22−1/4
(549) (511) (565)
19 20 19−5/8
(483) (508) (498)
19 20−1/4 20−5/8
(483) (514) (600)
19 20
(483) (508) (508)
23−5/8 22−1/4
(537) (600) (565)
19 23−1/2 19−5/8
(483) (597) (498)
19 23−3/4 20−5/8
(483) (603) (600)
19 23−1/2
(483) (597) (508)
D
20
20
20
20
13