AEC NEC Central Station Air and Water Cooled Chiller - Manual (Page 43)

Page 42 NEC Series Water- and Air-Cooled Central Chillers
Low Oil Pressure (OIL)
This indicator lights if compressor oil pressure is too low. After two minutes of low oil pressure,
the chiller shuts down. This manual reset control should be reset by a qualified refrigeration
service technician.
High Refrigerant Pressure (HI)
This indicator lights if the condensing pressure is too high. The chiller goes into an idle mode
until the High Pressure Cutout is manually reset by a qualified refrigeration service technician.
Power Light (ON)
This green indicator lights when the main power switch is ON and the control circuit is
energized. The crankcase heater is energized whenever main power is applied, regardless of
the power switch position.
System Staging Lights
These amber lights provide a rough approximation of the load on the chiller relative to its
capacity. The number of lights depends on the size of the system. They do not represent a
percentage of the true capacity of the unit, except when they indicate that the refrigeration circuit
is off or fully loaded.
6-2 Switches
Figure 16
Power Main (Control)
This toggle switch energizes the control circuit. On multiple circuit chillers, it energizes the
common part of the control circuit. The crankcase heater remains energized whenever main
power is applied, regardless of switch position.
Power Circuit 1, 2, or 3
These toggle switches energize the separate refrigeration circuits. This permits shutting down
one circuit if there is a failure, to isolate the circuit or to perform periodic maintenance while
other refrigeration circuit(s) remain on. Switches 2 and 3 will, of course, be found only on two
and three circuit units. The crankcase heater is energized whenever main power is applied,
regardless of the power circuit switch position.