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SECTION 4
CONTROLS & INSTRUMENTATION
GENERAL – The Gardner Denver Electra–Screw
compressor is supplied with a factory mounted starter
and complete controls as standard equipment. The
standard control system consists of constant run load/
unload operation, or auto start/timed stop operation.
Lead/Lag operation of two Electra–Screw compres-
sors is also possible without additional equipment.
PROTECTIVE DEVICES – All compressors incorpo-
rate the following protective devices:
Motor Protection Devices – Overload relays are fur-
nished for each motor in the voltage range specified.
There are six (6) heaters, sized as indicated in the chart
in the starter box. An trip of either relay is indicated by
the "MOTOR OVERLOAD" LED located on the control
keypad.
Separator Differential Pressure – The separator dif-
ferential pressure is continually monitored by the mi-
croprocessor controller. At a differential of approxi-
201EBB797
(Ref. Drawing)
mately 8 PSI, the "CHANGE SEPARATOR" LED
located on the control keypad flashes indicating re-
quired maintenance. If the warning is ignored, and the
separator differential continues to increase, the micro-
processor controller will stop the unit and the LED will
remain on steady. See "Control System Operation,"
page 17, for further information on operation of the mi-
croprocessor controller.
High Discharge Temperature – The compressor is
protected from high discharge temperature by two in-
dependent thermistor probes. One probe is located in
the compressor discharge housing to sense compres-
sor discharge air–oil mixture temperature. The second
probe is located at the separator discharge and senses
the temperature of the air at the oil separator.
The microprocessor controller will shut the compressor
down if the temperature sensed at either location ex-
ceeds 225 F. See "HIGH AIR TEMPERATURE" LED,
page 18.
FIGURE 4–1 – CONTROL SCHEMATIC
13–8–612
Page 15
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