Ingersoll-Rand 900829, Руководство по обслуживанию

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General Description
23
Evaporator Drain Tube Heaters
Evaporator heaters are used in R-404A units to
avoid drain tube blockage because of ice
accumulation inside the evaporator. Two
harnesses are located inside the drain tube. These
resistive wires melt the ice while the unit is in
Defrost mode.
Electric Standby Operation
When the unit is connected to an electric power
source, the battery disconnect relay and the
standby relay are energized and provide rectified
power from the transformer to the electronic
control system.
During electric standby operation, the electronic
control system controls the operation of the unit
by energizing and de-energizing the compressor
contactor.
The electronic control system places the unit in
cool, heat or defrost by energizing the compressor
contactor.
The electronic control system places the unit in
null by de-energizing all the compressor
contactor.
Protection Features
• High Pressure Transducer - The high pressure
transducer is a pressure sensitive device. It is
located in the discharge line near the oil
separator or the discharge check valve.
If the discharge pressure rises above a certain
pressure, the ECM opens the circuit to the
compressor clutch to stop the unit.
For units with R-134a, the ECM opens the
compressor clutch circuit at 300 psig (2068
kPa) and shuts down the unit. The ECM closes
when the pressure drops to 200 psig (1379
kPa).
For units with R-404A, the ECM opens the
compressor clutch circuit at 450 psig (3103
kPa) and shuts down the unit. The ECM closes
the compressor clutch circuit when the
pressure drops to 375 psig (2586 kPa).
• Low Pressure Cutout Switch - The Low
Pressure Cutout Switch is a pressure sensitive
switch located in the suction line. If the
pressure falls below 5 to 11 in. Hg vacuum
(-17 to -34 kPa), the switch opens the
LPCO/CH circuit. This signals the ECM to
open the circuit to the compressor clutch to
stop unit operation.
Control Box
P.C. Board
All Printed Circuit Boards manufactured by
Thermo King can be easily identified by the Part
Number stamped on them.
Connectors
All connector codes (C-1, C-2, etc.) are stamped
on the P.C. Board. Pins on the connectors are
numbered counter-clockwise.
Electronic Control Module (ECM)
The ECM contains the system’s secondary
microprocessors, I/O connectors, output relays,
fuses, LEDs, cooling fan, and discrete electronic
components mounted on two printed circuit
boards PCB2 is mounted on top of PCB1. This
configuration is known as Platform 2.
The microprocessors receives output signals from
the load compartment return air sensor and
electronic thermostat. These signals are sent to the
microprocessor in the In-Cab Control Box. Based
on setpoint temperature and other parameters, the
In-Cab Control Box microprocessor determines
when to adjust the temperature-control state in the
load compartment to Cool, Heat, or Null mode, or
to initiate a Defrost cycle.