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INSTALLATION
Step 1 — Provide Unit Support
ROOF CURB
For vertical discharge units, assemble or install accessory roof
curb in accordance with instructions shipped with this accessory.
See Fig. 2-5. Install insulation, cant strips, roofing, and counter
flashing as shown. Ductwork can be installed to roof curb before
unit is set in place. Curb should be level. This is necessary to per
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mit unit drain to function properly. Unit leveling tolerance is
shown in Fig. 2-5. Refer to Accessory Roof Curb Installation In
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structions for additional information as required. When accessory
roof curb is used, unit may be installed on class A, B, or C roof
covering material.
ALTERNATE UNIT SUPPORT
When the preferred curb or slab mount cannot be used, support
unit with sleepers on perimeter, using unit curb support area. If
sleepers cannot be used, support long sides of unit (refer to Fig. 6-
14) with a minimum number of 4-in. x 4-in. pads spaced as fol
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lows: 50A020-035 units require 3 pads on each side; 50A040-050
units require 4 pads on each side; 50A060 units require 6 pads on
each side. Unit may sag if supported by corners only.
Step 2 — Rig and Place Unit
Inspect unit for transportation damage. See Tables 1-6 for physical
data and specifications. File any claim with transportation agency.
Do not drop unit; keep upright. Use spreader bars over unit to pre
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vent sling or cable damage. This unit must be handled with a crane
and cannot be handled by a fork truck. Level by using unit frame
as a reference; leveling tolerance is shown in Fig. 2-5. See Fig. 15
for additional information. Unit operating weight is shown in Ta
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bles 2-5.
NOTE: On retrofit jobs, ductwork may be attached to the old unit
instead of a 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. 6-14. Refer to rigging instructions on unit.
POSITIONING
Maintain clearance (see Fig. 6-14) around and above unit to pro
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vide minimum distance from combustible materials, proper air
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flow, and service access.
Do not install unit in an indoor location. Do not locate unit air in
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lets 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 distribution requirements. See
Fig. 15. Unit operating weight is shown in Tables 2-5.
Step 3 — Field Fabricate Ductwork
Secure all ducts to building structure. Use flexible duct connectors
between 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 and return
ductwork, provisions should be made for servicing of the outdoor
air filters (i.e., catwalk over ductwork).
Ducts passing through an unconditioned space must be insulated
and covered with a vapor barrier. Outlet grilles must not lie direct
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ly below unit discharge. The return duct must have a 90-degree el
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bow 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.
Follow AMCA (Air Movement and Control Association) guide
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lines relating to ductwork connections to the unit. These guide
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lines recommend a minimum 2
1
/
2
equivalent duct diameters of
straight duct connected to supply air inlet and outlet openings be
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fore any transitions, fittings, dampers, etc. Failure to adhere to
these guidelines may result in system effects which can impact the
unit’s ability to achieve published performance.
Step 4 — Make Unit Duct Connections
50A2,A3,A6,A7 UNITS
Unit is shipped for thru-the-bottom duct connections. Field-
fabricated ductwork should be attached to the roof curb. Sup
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ply and return duct dimensions are shown in Fig. 6, 7, 10, and
12. Air distribution is shown in Fig. 16. Refer to installation in
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structions shipped with roof curb for more information.
50A4,A5,A8,A9 UNITS
Remove shipping covers from supply and return air openings. At
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tach field-supplied ductwork to unit. Connect to the unit with a
single duct for all supply openings and with a single duct for all re
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turn openings. Splitting of the airflow into branch ducts should not
be done at the unit. Sufficient duct length should be used prior to
branching to ensure the air temperatures are well mixed within the
ductwork. See Fig. 8, 9, 11, and 13 for duct opening dimensions.
Secure all ducts to building structure. Air distribution is shown in
Fig. 8, 9, 11, 13, and 17. Verify the Outdoor Air Temperature
(OAT) and Return Air Temperature (RAT) sensors as outlined in
Fig. 18 can measure the OAT and RAT temperatures in the corre
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sponding air streams. Relocate the sensor locations if needed. Fail
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ure to do this can lead to operational issues and possible future re
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location of the sensors.
Install accessory barometric relief or power exhaust in the field-
fabricated return ductwork. Refer to Step 8 — Position Power Ex
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haust/Barometric Relief Damper Hood section on page 28 for
more information.
Instructions continued on page 22.
CAUTION
1. All panels must be in place when rigging or damage to
unit may occur.
2. Unit is not designed for handling by fork truck. Damage
to unit may occur.
IMPORTANT: The gasketing of the unit to the roof curb is
critical for a watertight seal. Install gasket with the roof curb as
shown in Fig. 2-5. Improperly applied gasket can also result in
air leaks and poor unit performance.
WARNING
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. Use the full opening of the provided supply and return
openings. Failure to do so can lead to air balancing issues,
improper operation, or even failure of system components.
