TK 61753-2-MM-EN
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NNootteess::
1. ETV Operation and Null mode ONLY if controller setpoint is below Fresh/Frozen temperature setting
2. Null mode if setpoint is below Fresh/Frozen temperature setting.
3. During Cycle Sentry Operation:
• After initial unit start-up and unit pull-down to setpoint, the controller limits Low Speed Cool operation
when the controller setpoint is below Fresh/Frozen temperature setting. On increasing compartment
temperature, the unit operates in Low Speed Cool for a maximum of 8 minutes in an attempt to reach
setpoint. If setpoint is not reached within 8 minutes, the unit will operate in High Speed Cool until
setpoint is reached
• Unit mode is Null when the engine temperature and battery are satisfied.
Defrost
Frost gradually builds-up on evaporator coils as a result of normal operation. The unit uses hot refrigerant to defrost the
evaporator coils. Hot refrigerant gas passes through the evaporator coil and melts the frost. The water flows through
collection drain tubes onto the ground. The methods of Defrost initiation are Automatic and Manual.
AAuuttoommaattiicc DDeeffrroosstt:: The controller is programmed to automatically initiate timed or demand defrost cycles. The
controller can be programmed to initiate timed defrost cycles at intervals of 2, 4, 6, 8, or 12 hours. Demand defrost
cycles occur if the differences between the return air temperature, discharge air temperature, and coil temperature
exceed certain limits. The unit can enter defrost cycles as often as every 30 minutes if required.
MMaannuuaall DDeeffrroosstt:: In Manual Defrost Mode, the operator initiates a defrost cycle. See the appropriate Diagnostic or
Operator’s Manual.
NNoottee:: The unit will not perform a Manual Defrost cycle unless the unit has been turned on with the ON key, the unit is
running in Continuous or CYCLE-SENTRY mode (or shut down in CYCLE-SENTRY Null mode), and the coil
temperature is below 45 F (7 C).
The evaporator coil temperature must be below 45 F (7 C) to allow defrost.
The following four defrost timers are used. These timers can be set for intervals of 2, 4, 6, 8 or 12 hours.
• Defrost Interval In Range with Fresh Setpoint (standard setting 6 hours)
• Defrost Interval Not In Range with Fresh Setpoint (standard setting 4 hours)
• Defrost Interval In Range with Frozen Setpoint (standard setting 6 hours)
• Defrost Interval Not In Range with Frozen Setpoint (standard setting is 4 hours)
This feature allows a shorter Defrost interval to be used when the unit is out of range during a pull-down and more
frequent Defrost cycles may be beneficial.
Normally, longer defrost timer intervals are used for colder loads. The defrost interval may need to be changed if the
unit will not hold the compartment temperature at setpoint.
Use a longer defrost interval if defrost is not being initiated on demand.
Use a shorter defrost interval if defrost is frequently being initiated on demand.
If the unit is in CYCLE-SENTRY Null mode, the engine will start when defrost is initiated. The unit will stay in defrost
until the evaporator coil temperature rises to 58 F (14 C).
Engine Compartment Components
The following maintenance items can be checked visually.
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CCoommpprreessssoorr OOiill SSiigghhtt GGllaassss:: Use this sight glass to check the compressor oil level. See the Refrigeration Maintenance
section for the correct procedure.
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