York R134A manual Guide Specifications – continued, Compressors And Motors

Guide Specifications – continued

system, interconnecting wiring, safety and operating controls including capacity controller, control center, motor starting components, and special features as specified herein or required for safe, automatic operation.

C.Operating Characteristics:

1.Provide low ambient control and high ambient options as required to ensure unit is capable of operation from 0°F to 125°F (-18°C to 52°C) ambient.

2.Provide capacity control system capable of reducing unit capacity to (10% for 2 compres- sor units and 7.5% for 3 compressor units) of full load. Compressor shall start in unloaded condition. Application of factory installed hot gas bypass shall be acceptable as required to meet specified minimum load.

D.Cabinet: Unit panels, structural elements, control boxes and heavy gauge structural base shall be constructed of galvanized steel. Unit panels, control boxes and structural base are finished with a baked on powder paint. All painted surfaces shall be coated with baked on powder paint which, when subject to ASTMB117, 1,000 hour, 5% salt spray test, yields minimum ASTM 1654 rating of “6”.

E.Unit shall ship in one piece and shall require installer to provide only a single evaporator inlet and outlet pipe connection. If providing chiller model that ships in multiple pieces, bid shall include all the material and field labor costs for factory authorized personnel to install a trim kit to connect the pieces as well as all interconnecting piping and wiring.

2.02 COMPRESSORS AND MOTORS

A. Compressors: Shall be direct drive, semihermetic, rotary twin-screw type, including: muffler, tempera- ture actuated ‘off-cycle’ heater, rain-tight terminal box, discharge shut-off service valve, and precision machined cast iron housing mounted on neoprene isolators Design working pressure of entire compres- sor, suction to discharge, shall be 350 PSIG (24bar) or higher. Compressor shall be U.L. Recognized.

B.Motors: Refrigerant suction gas cooled accessible hermetic compressor motor, full suction gas flow through 0.006” maximum mesh screen, with inher- ent internal thermal overload protection and external current overload on all three phases.

C.Lubrication: External oil separators with no moving parts, 450 PSIG design working pressure, and UL listing. Refrigerant system differential pressure shall

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provide oil flow through service replaceable, 0.5 micron, full flow, cartridge type oil filter internal to compressor. Filter bypass, less restrictive media, or oil pump not ac- ceptable.

D.Capacity Control: Compressors shall start at minimum load. Provide Microprocessor control to command com- pressor capacity to balance compressor capacity with cooling load. When required to meet minimum load, hot gas bypass shall be factory installed and integrated into standard control system.

2.03 REFRIGERANT CIRCUIT COMPONENTS

A. Each independent refrigerant circuit shall include: liquid line shutoff valve with charging port, low side pressure relief device, removable core filter-drier, sight glass with moisture indicator, and electronic expansion valve.

B.Chiller manufacturer shall provide independent circuit for each compressor to provide maximum redundancy. If equipment does not have independent circuits per compressor, manufacturer shall provide owner one spare compressor of each unique size.

C.Discharge lines shall be provided with manual compres- sor shutoff service valves. Suction line shall be covered with closed cell foam insulation.

2.04HEAT EXCHANGERS A. Evaporator:

1.Direct expansion type or flooded type shell and tube evaporator with high efficiency copper tubes.

Independent refrigerant circuits shall be provided per compressor.

2.Constructed, tested, and stamped IAW applicable sections of ASME pressure vessel code for mini- mum 235 PSIG (16 bar) refrigerant side design working pressure and 150 PSIG (10 bar) water side design working pressure.

3.Shell covered with 3/4” (19mm), flexible, closed- cell insulation, thermal conductivity of 0.26k (BTU/HR-Ft2-°F/in.) maximum. Water nozzles with grooves for mechanical couplings, and insulated by Contractor after pipe installation.

4.Provide vent and drain fittings, and thermostati- cally controlled heaters to protect to -20°F (-29°C) ambient in off-cycle.

B. Air Cooled Condenser:

1.Coils: Internally enhanced, seamless copper tubes, mechanically expanded into aluminum alloy fins

JOHNSON CONTROLS