York 28971AR manual Refrigerant Circuit Components, Heat Exchangers, Controls

Guide Specifications (Continued)

valve to command compressor capacity independent of control valve input pressure and balance compres- sor capacity with cooling load.

2.03REFRIGERANT CIRCUIT COMPONENTS

Each independent refrigerant circuit shall include: liq- uid line shutoff valve with charging port, low side pres- sure relief device, removable core filter-drier, solenoid valve, sight glass with moisture indicator, thermostatic expansion valves, and flexible, closed-cell foam insu- lated suction line.

2.04HEAT EXCHANGERS

A.Evaporator:

1.Direct expansion type with refrigerant inside high efficiency copper tubes, chilled liquid forced over the tubes by galvanized steel baffles. Indepen- dent refrigerant circuits per compressor.

2.Constructed, tested, and stamped in accordance with applicable sections of ASME pressure ves- sel code for minimum 350 PSIG (24 bar) refriger- ant side design working pressure and 150 PSIG (10 bar) water side design working pressure.

3.Shell covered with ¾ " (19mm), flexible, closed- cell insulation, thermal conductivity of 0.26k ([BTU/HR-Ft2-°F]/in.) maximum. Water nozzles with grooves for mechanical couplings, and insu- lated 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 al- loy fins with full height collars. Subcooling coil an integral part of condenser. Design working pres- sure shall be 450 PSIG (31 bar).

2.Fans: Shall be dynamically and statically bal- anced, direct drive, corrosion resistant glass fi- ber reinforced composite blades molded into low noise, full airfoil cross section, providing vertical air discharge from extended orifices for efficiency and low sound. Each fan in its own compartment to prevent cross flow during fan cycling. Guards of heavy gauge, PVC (polyvinyl chloride) coated or galvanized steel.

3.Fan Motors: High efficiency, direct drive, 6-pole, 3-phase, insulation class “F”, current protected, Totally Enclosed Air-Over (TEAO), rigid mounted, with double sealed, permanently lubricated, ball bearings.

C. Refrigerant Economizer (when provided): Stainless steel plate type, oven brazed with copper, U.L./cU.L. Listed, 450 PSIG (31 bar) design working pressure.

2.05CONTROLS

A. General: Automatic start, stop, operating, and pro- tection sequences across the range of scheduled conditions and transients.

B. Control Circuit Transformer: Factory mounted with primary breaker having lockable, external handle, and 115V/1Ø secondary.

C. Microprocessor Enclosure: Rain and dust tight NEMA 3R/12 (IP55) powder painted steel cabinet with hinged, latched, and gasket sealed door.

D. Microprocessor Control Center:

1.Automatic control of compressor start/stop and load/unload, anti-coincidence and anti-recycle tim- ers, automatic pump-down at start-up and shut- down, condenser fans, evaporator pump, evapo- rator heater, unit alarm contacts, run signal con- tacts, and chiller operation from 0°F to 125°F (-18°C to 52°) ambient. Automatic reset to nor- mal chiller operation after power failure.

2.Setpoint Reset:

a.Pulse Width Modulated (PWM) input to reset current unload setpoint downward via signal from external Energy Management System (EMS), maximum allowable reset program- mable from microprocessor keypad.

b.PWM input to reset the chilled liquid setpoint upward via signal from remote EMS, maxi- mum allowable reset programmable from mi- croprocessor keypad.

3.Software stored in non-volatile memory, with pro- grammed setpoints retained in lithium battery backed real time clock (RTC) memory for mini- mum 5 years.

4.Forty character liquid crystal display, descriptions in English (or Spanish, French, Italian, or Ger- man), numeric data in English (or Metric) units. Sealed keypad with sections for Setpoints, Dis- play, Entry, Print, Program, Clock, and Unit On/ Off Switch.

5.Programmable Setpoints (within Manufacturer limits): display language; discharge pressure un- load and cutout; low suction pressure cutout; low and high ambient cutouts; leaving chilled liquid temperature: setpoint, control range, and cutout; high motor current unload; anti-recycle time; lag compressor start; local or remote control; units of measure; compressor lead/lag; power failure restart (auto or manual), and maximum EMS- PWM reset temperature range.

98 YORK INTERNATIONAL