Ingersoll-Rand 900829, Maintenance Manual

Page: 23 / 142

General Description
21
Compressor
Refrigeration hoses or lines are used to connect
the condenser, the evaporator, the main
compressor and any other refrigeration
components.
Model 20 and 50 units have an electric
compressor mounted in the condenser section for
electric standby operation. The electric standby
compressor is connected in parallel with the
engine-driven compressor.
Both compressors use the same refrigeration
system circuit. Check valves isolate one
compressor from the other during operation.
Compressor operation is controlled by the
electronic control system, which energizes the
compressor clutch during engine operation or
starts the electric compressor on electric standby
operation. The refrigeration system is protected
by a high pressure transducer and a low pressure
cutout switch.
When plugged into standby power, engine
operation is automatically locked out. If the truck
engine is turned on while the power cord is still
plugged into a power receptacle, the unit will
remain working in electric mode; the engine
driven compressor cannot be started until the
power cord is unplugged from the unit because the
selection of engine operation or standby operation
is automatic.
Control Circuits
The control circuits operate on 12V or 24V
supplied by the truck batteries for engine
operation. On standby operation, the power is
rectified from an AC transformer.
Electronic Control System
The Electronic Control System is composed of an
Electronic Control Module (located inside the
condenser unit) and the In-Cab Control Box. This
In-Cab Control Box allows the truck driver to
operate the Thermo King refrigeration unit.
Refer to the Direct Smart Reefer Microprocessor
Control System Diagnostic Manual TK 52573 for
complete service information about the Electronic
Control System and the related components.
Figure 2: In-Cab Control Box
The Electronic Control System has the following
characteristics:
• Auto Start
• Soft Start
• Active Display
• Lit Keypad
• Total Hourmeter
• Vehicle Compressor Hourmeter
• Electric Standby Compressor Hourmeter
• Low Battery Voltage Alarm
• Buzzer
• Unit Control without In-Cab Control Box
• Manual or Automatic Defrost
• Maintenance Warning
• Return Air Temperature Sensor
• Setpoint Temperature Reading
• Electric Power Warning
Auto Start:
Should the unit stop due to a failure in
the power supply, whether during on-the-road or
electric standby operation, it will start up again as
soon as the power supply is re-established.
Soft Start:
All operation modes remain inactive
for 15 seconds after an Auto Start.
Active Display:
The In-Cab Control Box display
is always active and backlit except when the unit
is disconnected (no power) or when the unit is
connected but has been manually switched off
from the In-Cab Control Box (when there is no
active alarm).