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NOTE: On retrofit jobs, ductwork may be attached to old unit
instead of roof curb. Be careful not to damage ductwork when
removing old unit. Attach existing ductwork to roof curb
instead of unit.
Four lifting lugs are provided on the unit base rails as shown
in Fig. 5-10. Refer to rigging instructions on unit.
POSITIONING — Maintain clearance, per Fig. 5-10, around
and above unit to provide minimum distance from combustible
materials, proper airflow, and service access.
Do not install unit in an indoor location. Do not locate unit
air inlets near exhaust vents or other sources of contaminated
air.
Although unit is weatherproof, guard against water from
higher level runoff and overhangs.
ROOF MOUNT — Check building codes for weight distribu-
tion requirements. See Fig. 11. Unit operating weight is shown
in Table 2.
Step 3 — Field Fabricate Ductwork —
ducts to building structure. Use flexible duct connectors be-
tween unit and ducts as required. Insulate and weatherproof all
external ductwork, joints, and roof openings with counter
flashing and mastic in accordance with applicable codes.
NOTE: Due to width of the horizontal supply/return ductwork,
provisions should be made for servicing of the outdoor air fil-
ters (i.e., catwalk over ductwork).
Ducts passing through an unconditioned space must be in-
sulated and covered with a vapor barrier. Outlet grilles must not
lie directly below unit discharge. The return duct must have a
90-degree elbow before opening into the building space if the
unit is equipped with power exhaust.
To attach ductwork to roof curb, insert duct approximately
10 to 11 in. up into roof curb. Connect ductwork to 14-gage
roof curb material with sheet metal screws driven from inside
the duct.
For vertical supply and return units, tools or parts could
drop into ductwork and cause an injury. Install a 90-degree
elbow turn in the supply and return ductwork between the
unit and the conditioned space. If a 90-degree elbow cannot
be installed, then a grille of sufficient strength and density
should be installed to prevent objects from falling into the
conditioned space.
Step 4 — Make Unit Duct Connections
50AJ AND AK UNITS — Unit is shipped for through-the-
bottom duct connections. Field-fabricated ductwork should be
attached to the roof curb. Supply and return duct dimensions
are shown in Fig. 5-7. Air distribution is shown in Fig. 12.
Refer to installation instructions shipped with roof curb for
more information.
50AW AND AY UNITS — Remove shipping covers from
Secure all
supply and return air openings. Attach field-supplied ductwork
to unit. Connect to the unit with a single duct for all supply
openings and with a single duct for all return openings.
Splitting of the airflow into branch ducts should not be done at
the unit. Sufficient duct length should be used prior to branch-
ing to ensure the air temperatures are well mixed within the
ductwork. See Fig. 8-10 for duct opening dimensions. Secure
all ducts to building structure. Air distribution is shown in
Fig. 8-10 and Fig. 13.
Install accessory barometric relief or power exhaust in the
field-fabricated return ductwork. Refer to Step 8 — Position
Power Exhaust/Barometric Relief Damper Hood section on
page 44 for more information.
2
Instructions continued on page 18.
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