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Return Duct Connection
Return air may enter the furnace through the side(s) or bottom
depending on the type of application. Return air may not be
connected into the rear panel of the unit. See the specific
type application installation for details. Be sure to see the
"Filters" section of this instruction.
UPFLOW FILTER INSTALLATION
All applications require the use of a filter. a high velocity filter
and retainer are provided for field installation.
Internal Installation
1. Select desired filter position (left/right side, or bottom).
Remove the corresponding cabinet cut-outs per instruc-
tions provided.
2. Install snap-in retainer clips into the corresponding slots
from the outside rear of the cabinet (refer to Figure 1). To
prevent cabinet air leaks, install snap-in plugs (provided)
into the unused slots at the outside rear of the cabinet.
FIGURE 1 - FURNACE FILTER SLOT LOCATIONS
3. Install the wire retainer inside the cabinet. Insert the open
ends of the wire retainer into the clip loops at the rear of
the blower compartment. The retainer wire should pivot
freely like a hinge, on the clips at the rear of the cabinet.
Refer to Figure 2.
FIGURE 2 - SIDE FILTER RETAINER PLACEMENT
Unitary Products Group
FIGURE 3 - SIDE RETURN CUTOUT MARKINGS
4. Install the filter(s) provided. Cut filter if necessary to match
air opening in cabinet. Filter should extend beyond opening
edge as much as possible to prevent air form bypassing
the filter. DO NOT remove stiffening rods from inside the
filter. Shorten the rods, if necessary, to match final filter
size.
5. Position the filter between the wire retainer and the cabinet
wall (or floor) so it completely covers the cabinet air
opening and secure the filter in place at the front of the
cabinet by fastening the closed (looped) end of the retainer
wire under the flanged edge of the cabinet. When properly
installed the filter should fit flush with all four sides of the
cabinet wall.
NOTE: Air velocity through throw-away type filters may not
exceed 300 feet per minute. All velocities over this
require the use of high velocity filters.
Side Return - External Filter
Locate and knock out the square corner locators. These indi-
cate the size of the cutout to be made in the furnace side panel
(see Figure 3).
Install the side filter rack following the instructions provided with
that accessory. If a filter(s) is provided at another location in
the return air system, the ductwork may be directly attached to
the furnace side panel.
NOTE: Some accessories such as electronic air cleaners
and pleated media may require a larger side opening.
CAUTION: All installations must have a filter installed.
The return duct may be attached to the furnace by "S-cleat",
bend tabs or other approved methods. Be sure to seal the duct
tot he furnace to prevent air leakage.
Those applications over 1800 CFM require either return from
two sides, one side and the bottom, or bottom only. For bottom
only application, see data and notes on blower performance
data tables in this manual.
Where the return duct system is not complete, the return
connection must run full size to a location outside the utility
room or basement. For further details, consult Section 5.3 ( Air
for Combustion and Ventilation) of the National fuel Gas Code,
ANSI Z223.1, or CAN/CGA B149.1 or .2, Installation Code -
latest editions.
650.75-N4U
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