Maintenance Inspection Schedule; Electronic Control System; Defrost System; Defrost Termination Switch - Thermo King V-220 Series Maintenance Manual

Electrical Maintenance

Maintenance Inspection Schedule

Inspect/Check/Service These Items
Check unit for any active alarms.
Check unit for proper defrost operation.
Inspect wiring harnesses and connectors.
Check return air temperature sensor calibration.
Inspect ground terminals.
W W A A R R N N I I N N G G
R R i i s s k k o o f f I I n n j j u u r r y y ! !
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a a c c c c i i d d e e n n t t a a l l l l y y s s t t a a r r t t w w h h i i l l e e y y o o u u a a r r e e s s e e r r v v i i c c i i n n g g t t h h e e
s s y y s s t t e e m m . . A A l l w w a a y y s s t t u u r r n n o o f f f f t t h h e e O O n n / / O O f f f f S S w w i i t t c c h h w w h h e e n n
i i n n s s p p e e c c t t i i n n g g o o r r s s e e r r v v i i c c i i n n g g a a n n y y c c o o m m p p o o n n e e n n t t s s . .

Electronic Control System

Refer to the Direct Smart Reefer III Microprocessor
Control System Diagnostic Manual TK 61096 for
complete service information about Electronic Control
System and the related components.

Defrost System

Defrost is initiated automatically by the programmable
defrost timer, or manually by means of the In-Cab
Control Box. If demand defrost is enabled, a demand
defrost cycle occurs, based on the Defrost Initiation
Timer (DIT) and the Defrost Termination Switch (DK1)
being closed. The evaporator coil temperature must be
below 36 F (2.2 C) to allow defrost.
When defrost is required, the microprocessor output
energizes the hot gas solenoid to supply hot refrigerant
to the evaporator coil and de-energizes the evaporator
fans. The Defrost Initiation Timer (DIT) has counted-
down its required time-setting, and the Defrost
Termination Switch (DK1) is closed.
The unit remains in Defrost mode until the Defrost
Termination Switch setpoint is reached (that is, when
the evaporator coil temperature rises to 48.0 F (8.9 C),
or until the Defrost Termination Timer (DTT) count is
completed). If the evaporator coil temperature does not
rise above 48.0 F (8.9 C) within the defrost duration
time limit, the microprocessor terminates the defrost
operation.
The startup of the evaporator fans is delayed for
several seconds after Defrost mode ends to prevent
water from the melting ice from being sprayed on the
load.
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Defrost initiation and termination settings are accessed
through the Guarded Access Menu. Refer to the Direct
Smart Reefer III Microprocessor Control System
Diagnostic Manual TK 61096 for instructions on the use
of Guarded Access Menu features.
The Defrost Initiation Timer offers programming
choices of 0 to 480 minutes, in increments of 30
minutes. The factory setting is 240 minutes. This
parameter allows maintenance personnel to set the
Defrost Initiation Timer. When it times-out, it switches
the unit from Cool mode to Defrost mode. The timer
counts all the time that the unit is in Cool mode. The
count resets when Defrost mode starts. If the timer is
set at 0 (zero), this is a test position. Defrost mode
starts in 15 seconds.
The Defrost Termination Timer offers programming
choices of 5 to 50 minutes, in increments of 5 minutes.
The factory setting is 30 minutes. This parameter
allows maintenance personnel to set the Defrost
Termination Timer, which begins counting from the
initiation of a Defrost mode. When the timer times-out,
the unit is switched from Defrost mode to Null mode.
The timer resets at the end of a Defrost mode, or after
the Defrost Termination Timer has timed-out. If the
timer is set at 0 (zero), this is a test position. Defrost
mode stops in 15 seconds.

Defrost Termination Switch

The switch is mounted in the evaporator coil and
controls the defrost cycle in response to the evaporator
coil temperature. The switch is closed when the
evaporator coil temperature is below 36 F (2.2 C), which
allows the unit to enter the defrost cycle.
When the unit does shift into a defrost cycle, the
evaporator fan stops, and heat from the hot refrigerant
gas melts the frost from the evaporator coil. The switch
opens and terminates the defrost cycle when the
evaporator coil temperature rises above 48 F (8.9 C).
12 24
Months Months
or 2000 or 4000
Hours Hours
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TK 56342-18-MM-EN