15780-4
PACKAGED ROOFTOP AIR HANDLING UNITS
Refrigerant Circuits: Each refrigerant circuit shall have independent fixed orifice or
thermostatic expansion devices, service pressure ports, and refrigerant line filter
driers factory installed. An area shall be provided for replacement suction line driers.
Evaporator and Condenser Coils: Microchannel coils shall be burst tested by the
manufacturer. Internally finned copper tubes mechanically bonded to a configured
aluminum plate fin shall be standard for evaporator coils Microchannel condenser
coils shall be standard on all units. Coils shall be leak tested to ensure the pressure
integrity. The evaporator coil and condenser coil shall be leak tested to 225 psig and
pressure tested to 450 psig. Sloped condensate drain pans shall be standard.
Outdoor Fans: The outdoor fan shall be direct-drive, statically and dynamically
balanced, draw-through in the vertical discharge position. The fan motors shall be
permanently lubricated and shall have built-in thermal overload protection.
Indoor Fan: Belt driven, FC centrifugal fans with adjustable motor sheaves. Units
shall have an adjustable idler-arm assembly for quick-adjustment of fan belts and
motor sheaves. All motors shall be thermally protected.
Controls: Unit shall be completely factory-wired with necessary controls and
contactor pressure lugs or terminal block for power wiring. Unit shall provide an
external location for mounting a fused disconnect device. A choice of microprocessor
or electromechanical controls shall be available. A centralized Microprocessor shall
provide anti-short cycle timing and time delay between compressors.
VAV Operation: The VFD shall receive a 0-10 Vde signal from the unit controls
based upon supply static pressure and shall cause the drive to accelerate or decelerate
as required to maintain the supply static pressure setpoint. When subjected to high
ambient return conditions the VFD shall reduce its output frequency to maintain
operation.
Roof Mounting Curb: May be supplied factory assembled or disassembled. Once the
mounting curb is set in position, it shall be secured together with 1/4-20 x 1/2" long
sheet metal screw. The mounting curb shall have duct flanges shipped with it and no
separate duct flanges need be purchased.
PART 3 - EXECUTION
3.1 INSTALLATION
A.
B.
Install the packaged unit in strict accordance with the manufacturer's instructions and
recommendations and as shown on the Drawings.
Roof Curb: Install unit level on structural curb. Coordinate roof penetrations and
flashing with roof construction. Secure unit to upper curb rail, and secure curb base
to roof framing with anchor bolts.
Install condensate drain, minimum connection size, with trap and indirect connection
to nearest roof drain or area drain.
Duct installation requirements are specified in other Division 15 Sections. Drawings
indicate the general arrangement of ducts. The following are specific connection
requirements:
1. — Install ducts to terminate at flexible connection.
2. Apply 2-inch thick blanket-type fiberglass insulation at ductwork connection
between RTU and ductwork.
Connect supply and return ducts to RTU with flexible duct connectors specified in
13089K
