2.1 EQUIPMENT Factory assembled, single-piece chassis, air-cooled liquid chiller. Contained within the unit cabinet shall be all factory wiring, piping, controls, refrigerant charge, and special features required prior to field start-u Materials of Construction: The base rail is industrial-quality, 7 ga, zinc-dipped galvanized frame (with Magni-coated screws). The cabinet shall be galvanized steel casing with a baked enamel powder or pre-painted finish. Painted parts shall withstand 1000 hours in constant neutral salt spray under ASTM B117 conditions with a 1 mm scribe per ASTM D1654. After the test, painted parts shall show no signs of wrinkling or cracking, no loss of adhesion, no evidence of blistering, and the mean creepage shall not exceed 1/4 in. (Rating ³ 4 per ASTM D1654) on either side of the scribe line. Fans: Condenser fans shall be variable speed, 9-blade airfoil cross-section, reinforced polymer construction, shrouded-axial type, and shall be statically and dynamically balanced with inherent corrosion resistance. The variable speed drives for condenser fans shall include a DC link reactor Air shall be discharged vertically upward. All VFDs on the chiller (compressor motors and fans) shall be fully air cooled and shall not require an additional glycol cooling system, thus avoiding the maintenance associated with such cooling systems. Fans shall be protected by coated steel wire safety guards. Fan blades shall have serrated edges to minimize the sound that is produced. Compressor/Compressor Assembly: Compressors shall be semi-hermetic twin screw type. Compressor motor shall be direct drive, VFD (variable frequency drive) controlled to match the load requirement, with a maximum speed of 5880 or 6300 rpm. The motors are protected by motor temperature sensors, and are suction gas cooled. In order to optimally match the building load, maximize chiller power factor and help equalize compressor run time, all chiller compressors must be VFD controlled. For improved reliability with fewer moving parts, the compressor shall not employ a slide valve. Capacity control shall utilize a VFD to unload each compressor from 100% to 25% full load, resulting in a chiller minimum load of less than 15%. A VI (volume index) valve shall be provided to optimize the efficiency at full and part load conditions. The VFD for each compressor motor shall include a DC link reactor. The compressor shall include an internal muffler to reduce pulsations in the system. All VFDs on the chiller (compressor motors and fans) shall be fully air cooled and shall not require an additional glycol cooling system. Compressor performance shall not rely on an internal Teflon[footnoteRef:1] coating. [1: ] Two (2) pass Flooded Evaporator with Heater: Shall be mechanically cleanable tubes in a shell-and-tube type evaporator with removable heads. Tubes shall be internally enhanced seamless-copper type rolled into tube sheets. Water Connections shall be Victaulic-type. Shell and evaporator heads shall be insulated with 3/4-in. PVC foam (closed-cell) with a maximum K factor of 0.28. Design shall incorporate 2 independent refrigerant circuits. Evaporator shall be tested and stamped in accordance with ASME Code for a refrigerant working side pressure of 220 psig (1517 kPa). Evaporator shall have a maximum water-side pressure of 300 psig (2068 kPa). Evaporator shall have an evaporator drain and vent. Low-ambient temperature protection: unit shall have factory-installed evaporator heater to protect evaporator from ambient temperature freeze down to 0°F (–17.8°C). Evaporator shall be provided with a factory-installed flow switch. Condenser: Coil shall be air-cooled Novation® heat exchanger technology (MCHX) and shall have a series of flat tubes containing a series of multiple, parallel flow microchannels layered between the refrigerant manifolds. Novation coils shall consist of a two-pass arrangement. Coil construction shall consist of aluminum alloys for fins, tubes, and manifolds in combination with a corrosion-resistant coating. Tubes shall be cleaned, dehydrated, and sealed. Assembled condenser coils shall be pressure tested at the coil factory at 660 psig (5448 kPa) and subsequently shall be leak tested at 145 psig ±5 psig (1000 kPa ±34.5 kPa) and pressure tested at 350 psig (2413 kPa) at final unit assembly. All refrigerant piping, entering and leaving the condenser coils, shall be located on only one side of the chiller. Refrigeration Components Refrigerant circuit components shall include replaceable-core filter drier, moisture indicating sight glass, electronic expansion valve, discharge service valves and liquid line service valves, and complete operating charge of both refrigerant and compressor oil.
