CRR-20 & CRR-40, September 1999
Operating Instructions
Unit Protection Devices
3-3
Unit Protection Devices
1.
CIRCUIT BREAKERS. A 25 ampere manual reset circuit
breaker protects the 460/380V power supply circuit to the
unit electric motors and control system transformer. The
main power circuit breaker is located in the control box.
2.
FUSES. A number of fuses located in the power module
protect unit circuits and components.
• A 2 amp fuse (F1) protects the circuit to the modulation
valve.
• A 1 amp fuse (F2) protects the bridge light relay (option)
circuit.
• A 1 amp fuse (F3) protects SPARE circuit terminals.
• A 5 amp fuse (F4) protects the circuit that supplies
power to Power Module Board.
• A 1 amp fuse (F5) protects the bridge light (option) cir-
cuit.
• A 5 amp fuse (F6) protects SPARE circuit terminals.
• A 3 amp fuse (F7) protects the TRANSFRESH (option)
circuit.
• A 2 amp fuse (F8) protects the IRMU (option) circuit.
• A 3 amp fuse (F9) protects SPARE circuit terminals.
• A 3 amp fuse (F10) protects the battery charger (option)
power input circuit.
• A 7.5 amp fuse (F11) protects the Output Module circuit.
• A 3 amp fuse (F12) protects the battery pack connector
circuit.
• A 3 amp fuse (F13) protects the battery charger (option)
output circuit.
• A 3 amp fuse (F14) protects the battery (option) circuit.
3. COMPRESSOR DISCHARGE GAS TEMPERATURE
SENSOR. A refrigerant injection system uses the com-
pressor discharge gas temperature sensor to determine
when cold refrigerant will be injected into the compressor
suction line. Liquid injection protects the compressor
from excessively high operating temperatures. At com-
pressor discharge gas temperature above 138 C (280 F),
the controller energizes the liquid injection valve. When
the discharge gas temperature drops to 132 C (270 F), the
controller de-energizes the injection valve to stop refriger-
ant injection.
If the discharge gas temperature rises above 148 C
(298 F), the controller immediately stops the compressor
and evaporator fans. The condenser fan and phase select
outputs remain energized as the controller operates the
condenser fan to correct the condition. The controller dis-
play will show “PAUSE ALM82” for 1 second every 10
seconds. After 5 minutes, the controller attempts to restart
the compressor. If the compressor still fails to start, fault
code 82 (Compressor Head Over Temperature) is generat-
ed. The controller will restart the compressor when the
fault condition corrects itself (resets).
4.
EVAPORATOR OVER TEMPERATURE PROTEC-
TION. An evaporator coil sensor monitors coil tempera-
ture during heat and defrost modes. If the coil sensor tem-
perature reaches 38 C (100 F), the controller de-energizes
the heater contactor. If the coil sensor reaches 50 C (122
F), the controller also de-energizes the evaporator fan and
phase select contactors; and generates a shutdown Alarm.
Fault code 09 (Evaporator Coil Over Temperature) is dis-
played on the controller display when the ALARM key is
pressed.
5.
HIGH PRESSURE CUTOUT (HPCO) SWITCH. The
refrigerant high pressure cutout opens, interrupting 24 Vac
control power to the compressor contactor if the compres-
sor discharge pressure rises above 2410 +/- 70 kPa, 24.10
+/- 0.7 bar, 350 +/- 10 psig. This immediately stops the
compressor and evaporator fans. The condenser fan and
phase select outputs remain energized as the controller
operates the condenser fan to correct the condition. The
controller display will show “PAUSE ALM10” for 1 sec-
ond every 10 seconds.
After 5 minutes, the controller attempts to restart the
compressor. If the compressor fails to start, fault code 10
(High Pressure Cutout) is generated. The controller will
restart the compressor when the fault condition corrects
itself (resets). The high pressure switch resets (closes)
when the pressure drops back to 1655 +/- 70 kPa, 16.55
+/- 0.7 bar, 240 +/- 10 psig.
6.
FUSIBLE PLUG FOR HIGH PRESSURE RELIEF. A
fusible plug is installed in the standard receiver tank to
avoid excessive pressure build-up within the refrigeration
system from extraordinary and unforeseen circumstances.
The plug blows when the plug temperature reaches 100 C
(212 F). The plug is located so that refrigerant pressure
expelled from the valve would be directed away from any-
one servicing the unit. The plug is non-repairable and
requires no adjustment. If the plug blows, recover the
remaining refrigerant charge and replace the fusible plug.
7.
HIGH PRESSURE RELIEF VALVE (OPTION). A high
pressure relief valve is installed in the water-cooled con-
denser-receiver tank to avoid excessive pressure build-up
within the refrigeration system from extraordinary and
unforeseen circumstances. The valve is a spring-loaded
piston that lifts when refrigerant pressure exceeds 3447
+345/-104 kPa, 34.47 +3.45/-1.04 bar, 500 +50/-15 psig.
The valve is located so that refrigerant pressure expelled
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