CSR-20 & CSR-40, September 1999
µ
P-D Controller
Output Module
4-43
9.
High Pressure Cutout (HPCO) and 24 Vac LEDs on the
Emergency Bypass Module turn ON to indicate normal
operation.
•
The HPCO LED is ON when the HPCO switch is
closed (normal) and turns OFF when the HPCO
switch is open (high discharge pressure).
•
THE 24 Vac LED is ON when 24 volt ac control
power is supplied to the Emergency Bypass Module
for Emergency Bypass unit operation.
NOTE: If emergency bypass procedures are used
under high ambient and high container (load) tem-
perature conditions, a compressor motor shutdown
may occur (indicating the compressor motor internal
overload protector has tripped). Wait a few minutes
to allow the overload protector to cool.
Output Module
The controller uses the output module to energize and de-ener-
gize unit contactors and solenoids. Controller commands are
transmitted from the controller to the output module through
the CAN terminal using serial communications commands.
Indicator LEDs on the Output Module turn ON to show an out-
put is energized. The RXD and TXD LEDs alternately flash
continuously to show the communications connection is good.
If one or both of the RXD and TXD LEDs do NOT flash, the
communications connection is open or defective. The output
module contains no user serviceable parts.
In the event the controller fails or the serial communica-
tions link between the output module and the controller fails,
the output module will operate the unit as follows:
• Chill (Fresh) Loads: Output module STOPS all compressor
and fan motor operation.
• Frozen Loads: Output module operates unit in Full Cool
mode.
Thermo Bus Tap
Serial communications commands are transmitted from the
µ
P-
D controller through the Thermo Bus Tap to the Output Module
on two wires (labeled blue and white). An open or defective
communications circuit is indicated when one or both of the
RXD and TXD LEDs on the Output Module do NOT flash.
In the event the serial communications link between the
output module and the controller fails, the output module will
operate the unit as follows:
• Chill (Fresh) Loads: Output module STOPS all compressor
and fan motor operation.
• Frozen Loads: Output module operates unit in Full Cool
mode.
Power Module
The power module supplies low voltage control power and
ground to the
µ
P-D controller and the Output Module. The
power module also supplies power to the modulation valve cir-
cuit and the serial communications line. Fuses on the printed
circuit board provide current overload protection to the unit
control circuits. The power module derives power from the
control power transformer. Always disconnect the main supply
power before working on the power module board.
µµ
P-D Output Module
