York STYLE A YCWS User Manual page 5

The Power and Control Panel shall be divided into a power
section for each electrical system, a common input sec-
tion and a control section.
Each power panel shall contain:
Compressor starting contactors, control circuit
serving compressor capacity control, compressor
contactor coils and compressor motor overloads. The
compressor motor overloads contain current trans-
formers which sense each phase, as an input to the
microprocessor, to protect the compressor motors
from damage due to: low input current, high input cur-
rent, unbalanced current, single phasing, phase
reversal, and compressor locked rotor.
The common input section shall contain:
The control supply transformer providing 115V, cus-
tomer relay board and control circuit switch discon-
nect/emergency stop device.
The control section shall contain:
On/Off rocker switch, microcomputer keypad and dis-
play, microprocessor board, I/O expansion board,
relay boards, and 24V fused power supply board.
MICROPROCESSOR CONTROLS
Fuzzy Logic control will be incorporated in the YCWS
range of chillers. Fuzzy Logic allows the control system
to monitor several key variables to provide tighter, more
stable chilled water temperature control. The control sys-
tem monitors the leaving chilled water temperature to
track where it has been, where it is now, how fast it is
moving, and accurately adjusts the chiller operation in
anticipation of expected performance to minimize hunt-
ing and save energy.
The microprocessor shall have the following functions
and displays:
• A liquid crystal 40 character display with text provided
on two lines and light emitting diode backlighting for
outdoor viewing.
• A color-coded, 35 button, sealed keypad with sec-
tions for Display, Entry, Setpoints, Clock, Print, Pro-
gram, and Unit On/Off Switch.
The standard controls shall include: brine chilling or ther-
mal storage, automatic pumpdown, run signal contacts,
demand load limit from external building automation sys-
tem input, remote reset liquid temperature reset input,
unit alarm contacts, chilled liquid pump control, automatic
YORK INTERNATIONAL
reset after power failure, automatic system optimization
to match operating conditions, software stored in non-
volatile memory (EPROM) to eliminate chiller failure due
to AC power failure.
The microprocessor can be directly connected to a YORK
ISN Building Automation System via the standard on-
board RS485 communications port. This option also pro-
vides open system compatibility with other communica-
tions networks.
Programmed Setpoints shall be retained in a lithium bat-
tery backed RTC with a memory of five years.
Display - In Imperial (°F and PSIG) or SI (°C and BAR)
units, and for each circuit:
• Return and leaving chilled liquid
• Day, date and time. Daily start/stop times. Holiday
and Manual Override status.
• Compressor operating hours and starts. Automatic
or manual lead/lag. Lead compressor identification.
• Run permissive status. No cooling load condition.
Compressor run status.
• Anti-recycle timer and anti-coincident start timer sta-
tus per compressor.
• Suction (and suction superheat), discharge, and oil
pressures and temperatures per System.
• Percent full load compressor motor current per phase
and average per phase. Compressor capacity con-
trol valve input steps.
• Cutout status and setpoints for: supply fluid tempera-
ture, low suction pressure, high discharge pressure
and temperature, high oil temperature, low and high
current, phase rotation safety, and low leaving liquid
temperature.
• Unloading limit setpoints for high discharge pressure
and compressor motor current.
• Liquid pull-down rate sensitivity (0.5°F to 5°F [0.3°C
to 3.0°C]/minute in 0.1°F [0.05°C] increments).
• Status of: evaporator heater, load and unload timers,
chilled water pump.
• Out of range message.
• Up to 6 fault shut down conditions.
• Standard Display Language is English, with an Op-
tion for Spanish.
Entry - Enter set point changes, cancel inputs, advance
day, change AM/PM.
Set Points - Chilled liquid temperature, chilled liquid
range, remote reset temperature range.
Clock - Time, daily or holiday start/stop schedule, manual
FORM 201.24-EG1
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