Thermo King 914970, Manual

Page: 89 / 186

Electrical Maintenance
89
line just past the receiver outlet check valve to the
accumulator inlet. The receiver outlet check valve
is located in the liquid line near the drier/receiver
outlet. This check valve prevents refrigerant from
migrating back into the receiver tank and
condenser during the Heat mode.
Cool Mode
The Cool mode has not been changed in the
TherMax
TM heating system. The TherMax TM
solenoid, which is normally closed, is
de-energized during the Cool mode. The
TherMax
TM solenoid separates the high side from
the low side. When the TherMax
TM
solenoid is
closed, it does not allow liquid refrigerant to flow
from the liquid line, through the TherMax
TM
solenoid line, to the accumulator.
Heat/Condenser Evacuation Mode
The unit will run in the Condenser Evacuation
mode for two minutes before entering the Heat
mode. This is accomplished by opening
(energizing) the TherMax
TM solenoid while the
unit is running in cool. The pressure difference
between the high pressure in the condenser and
the low pressure in the accumulator drives much
of the refrigerant out of the condenser and
receiver into the accumulator. The refrigerant is
then available for improved heating capacity. The
unit is placed in the Heat mode by opening
(energizing) the hot gas solenoid and closing
(energizing) the condenser inlet solenoid. The
TherMax
TM solenoid remains open while the unit
is in the Heat mode. The receiver outlet check
valve prevents the migration of refrigerant back
into the receiver tank and condenser.
Defrost Mode
The Condenser Evacuation mode is not used
before the Defrost mode. The TherMax
TM
solenoid, the hot gas solenoid, and the condenser
inlet solenoid are all energized at the same time.
The TherMax
TM solenoid remains open while the
unit is in the Defrost mode.
Start Up Mode
For the first 20 seconds when the unit is started it
runs in the Cool mode with the TherMax
TM
solenoid open and the alternator excitation circuit
(7K) de-energized. This reduces the load. The
Start Up mode is used for both diesel and electric
operation.
In-Cab TG-V Controller
Figure 16: Single Temperature In-Cab TG-V
Controller
(P/N 41-3305—12V No Modulation)
The In-Cab TG-V functions similarly to the
standard unit mounted TG-V. However, the
In-Cab TG-V Controller also has the following
additional features:
• Alarm Codes for Single Temperature In-Cab
TG-V.
• Power Cord LED on Model 50 Units.
• Whisper (Low Speed) Push Button.
Alarm
Code
Fault Condition
03 Return Air Sensor Faulty
04 Discharge Air Sensor Faulty
14 Defrost Circuit Failure
19 Engine Low Oil Pressure/High Water
Temperature
25 Battery Charging Alternator Failure
87 Field Test Error
88 Microprocessor Faulty