Mechanical Specifications

General

Units shall be specifically designed for outdoor rooftop installation on a roof curb and be completely factory assembled and tested, piped, internally wired, fully charged with R-22, compressor oil and shipped in one piece. Units shall be available for direct expansion cooling only, or direct expansion cooling with natural gas, electric, hot water or steam heating. Filters, outside air system, exhaust air system, optional non-fused disconnect switches and all operating and safety controls shall be furnished factoryinstalled. All units shall be UL approved and factory run tested. Cooling capacity shall be rated in accordance with ARI Standard 360. All units shall have decals and tags to aid in service and indicate caution areas. Electrical diagrams shall be printed on long life water resistant material and shall ship attached to control panel doors.

Casing

Exterior panels shall have a minimum of 1.25-ounce zinc coating per square foot of steel, phosphatized and painted with a slate grey finish which meets a 672 hour salt spray test based on the ASTM B117 standard for salt spray resistance. Screws shall be coated with zinc-plus-zinc chromate. Eighteen gauge steel hinged access panels with tiebacks to secure door in open position shall provide access to filters and heating sections. Refrigeration components, supply air fan and compressor shall be accessible through removable panels as standard. Unit control panel shall be accessible through hinged access panel with quick release latches. Double Wall Construction hinged access doors shall provide access to filters, return/exhaust air, heating and supply fan section. All access doors and panels shall have neoprene gaskets. Interior surfaces or exterior casing members shall have 1 /2-inch Tuf-Skin fiberglass insulation. Unit base shall be watertight with 14-gauge formed load bearing members, formed recess and curb overhang. Unit lifting lugs shall accept chains or cables for rigging. Lifting lugs shall also serve as unit tiedown points.

REFRIGERATION SYSTEM

Compressors

• 20 through 130 Ton Units Trane 3-D ® Scroll compressors have a simple mechanical design with only three major moving parts. Scroll type compression provides inherently low vibration. 3-D compliance provides a completely enclosed compression chamber which leads to increased efficiency. Exhaustive testing on the 3D Scroll, including start up with the shell full of liquid, has proven that slugging does not fail involutes. Direct-drive, 3600 rpm, suction gas-cooled hermetic motor. Trane 3-D Scroll compressor includes centrifugal oil pump, oil level sightglass and oil charging valve. Control of compressor shall allow lead/ lag of multiple compressors/circuits for even run time to increase life of compressors.

Evaporator Coil

Internally enhanced seamless copper tubing of 1 /2-inch O.D. shall be mechanically bonded to heavy-duty aluminum fins of configurated design.All coils shall be equipped with thermalexpansion valves and factory pressure and leak tested at 300 psi.

Condenser Coil

Configurated aluminum fin or configurated copper fin secondary surface shall be mechanically bonded to primary surface of 3 /8-inch O.D. seamless copper tubing for extra corrosion resistance. Subcooling circuit(s) shall be provided as standard. All coils shall be factory tested at 450 psig air pressure and vacuum dehydrated.

Condenser Fans and Motors

All condenser fans shall be vertical discharge, direct drive fans, statically balanced, with steel blades and zinc plated steel hubs. Condenser fan motors shall be three-phase motors with permanently lubricated ball bearings, built-in current and thermal overload protection and weathertight slingers over motor bearings.