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Oil Cooling
Oil cooling is provided by routing oil from the oil sep a -
ra tor through several of the top rows of the con dens er
coils and back to the compressor.
Capacity Control
The compressors will start at the minimum load po si tion
and provide a capacity control range from 10% - 100%
of the full unit load using a continuous function slide
valve. The microprocessor modulates a voltage signal to
a 3-way pres sure reg u lat ing capacity control valve which
controls com pres sor capacity, in de pen dent of system
pressures, and balances the com pres sor ca pac i ty with
the cool ing load. Loading is ac com plished by varying
pressure through the pressure regulating ca pac i ty control
valve to move the slide valve against the spring pressure
to promote stable smooth loading.
Automatic spring return of the slide valve to the min-
i mum load position will ensure compressor start ing at
min i mum motor load.
Power and Control Panel
All controls and motor starting equipment are factory
wired and function tested. The panel enclosures are
de signed to IP55 and are manufactured from powder
paint ed galvanized steel.
The Power and Control Panel are divided into power
sec tions for each compressor and associated fans, a con-
trol section and an electrical options section. The pow er
and control sections have separate hinged, latched, and
gasket sealed doors equipped with wind struts, (Fig #1,
page 12).
Each power compartment contains:
Compressor and fan starting contactors, fan motor
ex ter nal overloads, control circuit serving compressor
ca pac i ty control, compressor and fan contactor coils and
compressor motor overloads.
Current transformers in the 2ACE module provide for
the compressor motor over load protection and sense
current in each phase. This protects the compressor
motors from dam age due to: low current input, high
input current, un bal anced current, single phasing, phase
reversal, and com pres sor locked rotor.
The control section contains:
ON/OFF switch, microcomputer keypad and display,
mi cro pro ces sor board, I/O expansion board, relay boards
and power supply board.
YORK INTERNATIONAL
The options sections contain:
A control circuit transformer complete with service
switch providing 115/1/60 Hz power to the unit con trol
system.
Electrical options as described in "Accessories and
Options."
Microprocessor Controls
The microprocessor has the following functions and
displays:
• A liquid crystal 40 character display with text pro-
vid ed on two lines and light emitting diode back-
light ing out door viewing.
• A color coded, 35 button, sealed keypad with sec-
tions for Display, Entry, Setpoints, Clock, Print,
Pro gram and Unit ON/OFF.
The standard controls shall include: brine chilling, ther-
mal storage, automatic pump down, run signal con tacts,
demand load limit from external building automation
sys tem input, remote reset liquid temperature reset in-
put, unit alarm contacts, chilled liquid pump control,
au to mat ic reset after power failure, automatic system
op ti mi za tion to match operating conditions.
The software is stored in non-volatile memory (EPROM)
to eliminate chiller failure due to AC power failure.
The Programmed Setpoint are stored in lithium battery
backed memory.
Motor Current Protection
The microprocessor motor protection provides high cur-
rent protection to assure that the motor is not damaged
due to voltage, excess refrigerant, or other problems
that could cause excessive motor current. This is ac-
com plished by sending a current signal pro por tion al to
motor current from the Motor Protector mod ule to the
Power Supply Board where the signals are conditioned
and rout ed to the I/O Expansion board to be multi-
plexed and sent to the Microprocessor Board. If the
motor cur rent exceeds the 115% FLA trip point after
3 seconds of op er a tion on either Wye-Delta or ACL
starters, the mi cro will shut the system down and lock
it out after one fault. A manual reset of the re spec tive
system switch is re quired to clear the fault and restart
the system. A thor ough check of the mo tor, wiring, and
refrigerant system should be done be fore restarting a
system that has fault ed on high motor current.
FORM 201.19-NM6 (804)
2
15
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Troubleshooting
