Thermo King 920000, Manual

Page: 48 / 190

Operating Instructions
48
Other Controls
Defrost Termination Switches:
A temperature
sensitive switch is mounted on each evaporator
coil. It is used to control Defrost. The switch
closes when the evaporator temperature drops to
42 F (6 C). This enables Defrost.
The switch opens when the evaporator
temperature rises to 52 F (11 C). This terminates
Defrost if the unit is in Defrost. It disables Defrost
if the unit is not in Defrost.
Air Switches:
The air switches sense the air
pressure difference between the evaporator coil
inlets and outlets. The switches automatically
place the units on Defrost when ice or frost builds
up on the coil to a point where the air flow across
the coil is restricted 40 to 50% of normal.
Unit Indicators
Hourmeter:
The hourmeter records the number of
hours the unit is in diesel operation for proper
maintenance intervals. An electric hourmeter
(hours in electric operation) and a total hourmeter
(total operating hours) are optional equipment.
Digital Thermometer:
A digital thermometer is
built into each thermostat. The thermometer
normally indicates the return air temperature.
Receiver Tank Sight Glass:
This sight glass is used
to check the amount of refrigerant in the system.
Compressor Oil Sight Glass:
The compressor oil
sight glass indicates the relative level of
compressor oil in the compressor sump.
Engine Oil Dipstick:
Use the engine oil dipstick to
check the engine oil level.
Coolant Tank:
This gauge indicates the engine
coolant level. If the pointer is in the FULL (white)
range, the coolant level is acceptable. If the point
is in the ADD (red) range, add coolant to the
expansion tank.
Unit Protection Devices
Engine Reset Switch:
A thermal type manual reset
switch protects the engine. The reset switch
contains a heater coil that is attached to a sensor
switch in the engine oil system, engine coolant
system and the (optional) CYCLE-SENTRY
system.
When the engine oil pressure is too low, when the
starter exceeds the cranking limit on Auto
Start/Stop operation, or when the engine coolant
temperature is too high, the coil in the reset switch
begins to heat up. In 20 to 40 seconds, the switch
will open and shut down the unit. To reset the
engine reset, press the engine reset button.
Overload Relay/Electric Motor Reset Switch
(Model 50):
The overload relay protects the
electric standby motor. The overload relay opens
the circuit from the linestarter to the electric motor
if the motor overloads for any reason, (e.g., low
line voltage or improper power supply) while the
unit is on Electric Standby operation. To reset the
electric motor, press the motor reset button which
is located on the high voltage box.
Control System Circuit Breaker:
The control
system remote reset circuit breakers are located in
the control box. They are designed to protect the
12 volt DC control circuit from overloads. To
reset the circuit breakers, turn the unit On/Off
switch to the Off position for 30 seconds.
Control Circuit Fuse:
Located between the battery
and the unit control circuits (typically inside the
battery box). At about 60 amps, the fuse will melt
and cut battery power to the unit.
Engine Coolant High Temperature Cutout:
The
engine coolant high temperature cutout is a
temperature sensitive switch located in the engine
cooling system.
The engine coolant high temperature switch will
close and trip the engine reset if the engine
coolant temperature is greater than 215 to 225 F
(102 to 107 C).
CAUTION: Do not remove expansion
tank cap while the coolant is hot.