15
Downflow Furnaces
• Toattachthereturnairducttothefurnace,bendthe
flanges on the furnace upward 90° with wide duct
pliers. See Figure 31 for furnace flange locations.
NOTE: If system installation includes AC coil casing,
bend the flanges on the coil casing upward 90° before
attaching the return air duct.
• Securethereturnairductworktothefurnaceorcoil
casing (if installed) with sheet metal screws. Make
sure the screws penetrate the sheet metal casing and
flanges.
• The supply air must be delivered to the heated space
by duct(s) secured to the furnace or coil box casing,
running full size and without interruption.
• To attach the supply air duct to upflow & horizontal
furnaces, bend the flanges on the furnace upward 90°
with wide duct pliers. See Figure 32 for furnace flange
locations. NOTE: If system installation includes AC coil
casing, bend the flanges on the coil casing upward 90°
before attaching the supply air duct.
• Position the supply air ductwork onto the furnace
ensuring even alignment of furnace air opening and
supply air duct. NOTE: The ductwork must have an
opening equal to that of the supply air opening of the
furnace. See Figure 31 (page 32) and Figure 32 (page
33)
for supply air opening size.
Damping ducts, flexible vibration isolators, or pleated
media-style filters on the return air inlet of the furnace
may be used to reduce the transmission of equipment
noise eminating from the furnace. These treatments can
produce a quieter installation, particularly in the heated
space. However, they can increase the pressure drop in
the duct system. Care must be taken to maintain the proper
maximum pressure rise across the furnace, temperature
rise and flow rate. This may mean increasing the duct size
and/or reducing the blower speed. These treatments must
be constructed and installed in accordance with NFPA and
SMACNA construction standards. Consult with local codes
for special requirements. For best sound performance,
install all the needed gaskets and grommets around
penetrations into the furnace, such as for electrical wiring.
FURNACE INSTALLATION
GUH92A, GUH95A & GUH95C series gas furnaces offer
a wide range of installation options, including installation
in the upflow or horizontal positions with either right, left,
or upflow return air. GDD92A & GDD95A series gas
furnaces may only be installed as a downflow application.
• The furnace must be leveled at installation and
attached to a properly installed duct system. See
Figure 1 (page 6) for the required clearances needed
to move the furnace to its installation point (hallways,
doorways, stairs, etc).
• The furnace must be installed so that all electrical
components are protected from water.
• The furnace must be installed upstream from a
refrigeration system. (If applicable)
• Thecabinetplugmustalwaysbeusedtoclosethehole
in the side of the furnace when rotating the inducer.
• The furnace requires special venting materials and
installation procedures. See
page 7, page 8, page
9
, page 10, page 11, page 12, & page 13 for
venting guidelines and specifications.
WARNING:
GUH92A, GUH95A & GUH95C series gas furnaces are
shipped with the bottom panel installed as shown in
Figure
32 (page 33)
. If the furnace is installed with side return
air, the bottom panel must not be removed. If the furnace
is installed with bottom return air, the bottom panel must
be removed. See Bottom Panel Removal on page 21.
WARNING:
GUH92A, GUH95A & GUH95C series gas furnaces can
be installed horizontally (Figure 11) in an attic, basement,
crawl space or alcove. It can also be suspended from a
ceiling in a basement or utility room in either a right to
left airflow or left to right airflow as shown in Figure 12
(page 16)
.
These furnaces are shipped with the bottom panel installed.
If the furnace is installed horizontally, remove the bottom
panel from the furnace before attaching the duct system.
See Bottom Panel Removal on page 21.
If installing the furnace with an evaporator coil (in an attic),
it is required that a drip pan be placed under the furnace.
If the installation is on a combustible platform as shown
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