13
PLENUM
OPENING
C
A
B
D
FLOOR
OPENING
A96283
Fig. 13 -- Floor and Plenum Opening Dimensions
Table 1 – Opening Dimensions -- In. (mm)
FURNACE
CASING
WIDTH
PLENUM OPENING
FLOOR OPENING
A
B
C
D
17---1/2
(445)
16
(406)
24---1/8
(613)
16---5/8
(422)
24---3/4
(629)
21
(533)
19---1/2
(495)
24---1/8
(613)
20---1/8
(511)
24---3/4
(629)
24---1/2
(622)
23
(584)
24---1/8
(613)
23---5/8
(600)
24---3/4
(629)
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 static pressure.
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 must also be handled by a 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.
Flexible connections should be used between ductwork and
furnace to prevent transmission of vibration. Ductwork passing
through unconditioned space should be insulated 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.
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.
Ductwork Acoustical Treatment
Metal duct systems that do not have a 90 degree elbow and 10 ft.
(3.0 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
Connect supply--air duct to 3/4--in. flange on furnace supply--air
outlet. The supply--air duct attachment must ONLY be connected
to furnace supply--/outlet--air duct flanges 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
FIRE HAZARD
Failure to follow this warning could result in fire, personal
injury, or death.
Never connect return--air ducts to the back of the furnace.
!
WARNING
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. 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.
Filter Arrangement
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in fire, personal
injury or death.
Never operate unit without a filter or with filter access door
removed.
!
WARNING
The air filter arrangement will vary due to return air configuration
and filter type. The filter may be installed in an external
Filter/Media cabinet (if provided) or the furnace blower
compartment. Factory supplied washable filters are shipped in the
blower compartment.
If a factory--supplied external Filter/Media cabinet is provided,
instructions for its application, assembly, and installation are
packaged with the cabinet. The Filter/Media cabinet can be used
with the factory--supplied washable filter or a factory--specified
high--efficiency disposable filter (see cabinet instructions).
If installing the filter in the furnace blower compartment, determine
location for filter and relocate filter retaining wire, if necessary. See
Table 2 to determine correct filter size for desired filter location.
Table 2 indicates filter size, location, and quantity shipped with
this furnace. See Fig. 2 for location and size of bottom and side
return--air openings.
355B
A
V
