Product Manual PM WSC/WDC 77
8. The main contactors shall have a normally open and a normally closed auxiliary
contact rated at 125VA pilot duty at 115 VAC. An additional set of normally open
contacts shall be provided for each MCR.
9. There shall be electronic overloads in each phase set at 107% of the rated load amps
of each motor. Overloads shall be manual reset and shall de-energize the main
contactors when the overcurrent occurs. The overloads shall be adjustable and
selected for mid-range. Overloads shall be adjusted for a locked rotor trip time of 8
seconds at full voltage and must trip in 60 seconds or less at reduced voltage (33%
of delta LRA).
10. Each starter shall have a current transformer and adjustable voltage dropping
resistor(s) to supply a 5.0 VAC signal at full load to the unit control panels.
11. Each starter shall be equipped with a line to 115 VAC control transformer, fused in
both the primary and secondary, to supply power to the control panels, oil heaters
and oil pumps.
12. Each starter shall include the following protective devices:
a) Phase failure and reversal protection
b) Stall protection
F. CONTROL PANELS
A microprocessor based control panel shall be furnished for each compressor and shall be
fully wired and factory-mounted on the chiller. The control panels shall be independent
allowing one compressor to operate with the other panel removed. The control panels shall
also be interconnected to provide lead and lag control as well as load balancing when two
compressors are running. The compressor with fewest starts will start first and the unit with
the most hours will shut off first. Each panel shall have the following features:
1. The display shall have a minimum of 160-character liquid crystal display and be
backlit with a light emitting diode. Messages shall be in plain English. Coded two or
three character displays are not acceptable.
2. The following information shall be available on the display with simple entry on the
keypad:
a) Entering and leaving chilled and condenser water temperatures
b) Evaporator, suction, discharge, condenser, and liquid temperatures
c) Suction and discharge superheat
d) Liquid subcooling, evaporator and condenser approach temperatures
e) Evaporator, condenser, and lift pressures
f) Oil feed and sump temperatures
g) Oil pump discharge and oil differential pressure
h) Motor amps and amps as a percent of rated load amps
i) Hours of operation and number of starts, time of last start and stop
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