ROOF CURB — For vertical discharge units, assemble or in- stall accessory roof curb in accordance with instructions shipped with this accessory. See Fig.
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.
ALTERNATE UNIT SUPPORT — When the preferred curb or slab mount cannot be used, support unit with sleepers on pe- rimeter, using unit curb support area. If sleepers cannot be used, support long sides of unit (refer to Fig.
Step 2 — Rig and Place Unit — Inspect unit for transportation damage. See Tables
Do not drop unit; keep upright. Use spreader bars over unit to prevent sling or cable damage. This unit must be handled with a crane and can not be handled by a fork truck. Level by using unit frame as a reference; leveling tolerance is shown in Fig.
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.
POSITIONING — Maintain clearance, per Fig.
Do not install unit in an indoor location. Do not locate unit air inlets near exhaust vents or other sources of contaminated air. For proper unit operation, adequate combustion and venti- lation air must be provided in accordance with Section 5.3 (Air for Combustion and Ventilation) of the National Fuel Gas Code, ANSI Z223.1 (American National Standards Institute).
Although unit is weatherproof, guard against water from higher level runoff and overhangs.
Locate mechanical draft system flue assembly at least 4 ft from any opening through which combustion products could enter the building, and at least 4 ft from any adjacent building. When unit is located adjacent to public walkways, flue assem- bly must be at least 7 ft above grade.
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 — Secure all 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 and return duct- work, provisions should be made for servicing of the outdoor air filters (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
To attach ductwork to roof curb, insert duct approximately
10 to 11 in. up into roof curb. Connect ductwork to
Follow AMCA (Air Movement and Control Association) guidelines relating to ductwork connections to the unit. These guidelines recommend a minimum 21/2 equivalent duct diame- ters of straight duct connected to supply air inlet and outlet openings before 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.
WARNING
For vertical supply and return units, tools or parts could drop into ductwork and cause an injury. Install a
Step 4 — Make Unit Duct Connections
48AJ AND AK UNITS — Unit is shipped for
48AW AND AY UNITS — Remove shipping covers from supply and return air openings. Attach
Install accessory barometric relief or power exhaust in the
Instructions continued on page 19.
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