Ingersoll-Rand 900829, Maintenance Manual

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39
Electrical Maintenance
Electronic Control System
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.
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 (DTS1 or DTS2)
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 defrost solenoid to supply hot
refrigerant to the evaporator coil. The Defrost
Initiation Timer (DIT) has counted-down its
required time-setting, and the Defrost Termination
Switch (DTS1 or DTS2) 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.
On multi temp units defrost is performed on all
evaporators at the same time.
Defrost initiation and termination settings are
accessed through the Guarded Access Menu.
Refer to the Direct Smart Reefer Microprocessor
Control System Diagnostic Manual TK 52573 for
instructions on the use of Guarded Access Menu
features.
The Defrost Initiation Timer offers programming
choices of 30 to 480 minutes, 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 45
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
Maintenance Inspection Schedule
Procedures Weekly Monthly
Semi-
Annual Annually
Check defrost initiation and termination. • •
Check thermostat cycle sequence. • •
Check operation of protection shutdown circuits. • •
Check thermostat and thermometer calibration in 32 F
(0 C) ice-water bath. •
Inspect wire harness for damaged wires or
connections. •
Inspect/replace DC fan motors. •
WARNING: Take precautions to ensure
the unit will not accidentally start while
you are servicing the system.