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912SD: Installation, Start-up, Operating and Service and Maintenance Instructions
humidifier, or other accessories. All supply-side accessories MUST be
connected to duct external to furnace casing.
Return Air Connections
WARNING
!
FIRE HAZARD
A failure to follow this warning could cause personal injury, death
and/or property damage.
Never connect return-air ducts to the back of the furnace. Follow
instructions below.
The return-air duct must be connected to return-air opening (bottom
inlet). DO NOT cut into casing sides (left or right). Bypass humidifier
connections should be made at ductwork or coil casing sides exterior to
furnace. See
Fig.
22.
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed in bottom
return-air opening. Remove and discard this panel when bottom return
air is used. To remove bottom closure panel, see
Horizontal Installation
NOTE: The furnace must be pitched forward as shown in
proper condensate drainage.
WARNING
!
FIRE, EXPLOSION, AND CARBON MONOXIDE
POISONING HAZARD
Failure to follow this warning could result in personal injury, death, or
property damage.
Do not install the furnace on its back or hang furnace with control
compartment facing downward. Safety control operation will be
adversely affected. Never connect return-air ducts to the back of the
furnace.
CAUTION
!
MINOR PROPERTY HAZARD
Failure to follow this caution may result in minor property damage.
Local codes may require a drain pan under entire furnace and
condensate trap when a condensing furnace is used in an attic
application or over a finished ceiling.
FURNACE
CASING WIDTH
IN. (mm)
Upflow Applications on Combustible or Noncombustible Flooring
Downflow Applications on Noncombustible Flooring
*
14–3/16
Downflow applications on combustible flooring
(360)
Downflow Applications on Combustible Flooring with coil assembly
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 assembly
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Fig.
24.
Fig. 19
Table 5 – Opening Dimensions - In. (mm)
APPLICATION
(Subbase not required)
(Subbase not required)
(Subbase required)
coil or coil box (Subbase not required)
(Subbase not required)
(Subbase not required)
(Subbase required)
coil or coil box (Subbase not required)
The furnace can be installed horizontally in an attic or crawlspace on
either the left-hand (LH) or right-hand (RH) side. The furnace can be
hung from floor joists, rafters or trusses or installed on a
non-combustible platform, blocks, bricks or pad.
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.
Connect supply-air duct to flanges on furnace supply-air outlet. Bend
flange upward to 90° with wide duct pliers. See
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 supply-side accessories MUST be connected to duct
external to furnace main casing.
Return Air Connections
for
FURNACE RELIABILITY HAZARD
Failure to follow this caution may result in unit component damage.
Return air connections to either side of the furnace in the horizontal
position can result in nuisance limit switch tripping. Use only the
factory bottom opening of the furnace for the return air connection.
The return-air duct can only be connected to bottom of the furnace. The
sides of casing cannot be used for return air connection. See
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed in bottom
return-air opening. Remove and discard this panel when bottom return
air is used. To remove bottom closure panel, see
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) are used without a bottom return air inlet.
Not all horizontal furnaces are approved for side return air connections
See
Fig.
23. Where required by code, seal bottom closure to furnace with
tape, mastic, or other durable sealing method.
PLENUM OPENING
A
12-11/16
(322)
12-9/16
(319)
11-13/16
(284)
12-5/16
(319)
16
(406)
15-7/8
(403)
15-1/8
(384)
15-1/2
(394)
17
Fig.
20. The supply-air
CAUTION
!
Fig.
24.
FLOOR OPENING
B
C
21-5/8
13-5/16
(549)
(338)
19
13-3/16
(483)
(335)
19
13-7/16
(483)
(341)
19
13-5/16
(483)
(338)
21-5/8
16-5/8
(549)
(422)
19
16-1/2
(483)
(419)
19
16-3/4
(483)
(425)
19
16-1/2
(483)
(419)
Fig.
23.
D
22-1/4
(565)
19-5/8
(498)
20-5/8
(600)
20
(508)
22-1/4
(565)
19-5/8
(498)
20-5/8
(600)
20
(508)
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