Controller Adjustment
Technical Catalogue
8
51
TCGB0051 rev 0 - 09/2009
8.2. Control System
Electrical Operation Control advanced HITACHI Condenser less Chillers are as follows.
¡ Capacity Control
All models are equipped with an unloading system for each compressor, in order to adjust the cooling
capacity and to provide precise temperature control for the chilled water, coupled with electronic
thermostats..
¡ Control Panel
ON switch, OFF switch, Power Supply Lamp, Operation Lamp, Alarm Lamp, Operation/Alarm Indicator for
each refrigerant cycle and check switch are mounted in the Control Panel. The Control Panel is located at a
position where easy access is available. Operation/Alarm indicator can display individual alarm codes such
as High-Cut, Low-Cut etc. this function is very useful for detecting what alarm has occurred. Check switches
are for checking chilled water temperature and alarm occurrence data. Chilled water temperature setting
switches, ON/OFF Differential Setting Switches, Remote-Local Switch and so on are located at the rear side
of Control Panel, in order not to access during operation.
¡ Operation Hour-Meter
This hour-meter indicates the sum of the compressor operation
¡ Printed Circuit Board
A micro-processor, relays and electronic components are mounted on the Printed Circuit Board. Increased
reliability is assured due to the elimination of mechanical parts and wires. This board contains various
function by applying micro-processor as follows:
Screw Compressor Cycling Protection Circuit.
The electronic timer of the screw compressor cycling protection (ccp) connected in the compressor
control circuit delays the screw compressor restarting period for approximately three (3) minutes for No.1
compressor, four (4) minutes for No.2 compressor.
Electronic Thermostat Circuit.
The electronic thermostat senses chilled water outlet temperature, and operate capacity control solenoid
valves of HITACHI screw compressor.
Screw Compressor Reversing Protection Circuit.
This circuit is composed of a reverse-phase protection devices, preventing reverse operation of the screw
compressor, because the screw compressor denitely cannot be operated in the wrong direction, due to the
misconnection of the main power phases.
Restart after Short Period Power-Failure.
In the case that a power failure shorter than 2 seconds occurred, compressors can be restarted automatically
within 3 minutes after power supply. If power failure longer than 2 seconds occurred, compressor can be also
restarted by selection switch setting.
Power Supply.
All models need only single power supply . Control circuit is powered from main power circuit. For remote
control, pump interlock and pump operation, see the diagram of “Customer Wiring”
8.3. Controller Adjustment
Layout of control panel of printed circuit board is shown in the Figure of the last page.
Setting functions are next:
¡ Chilled Water Outlet Temperature Setting Switch = RSW1 and RSW2
= 7°C for chilled water outlet temperature is recommended. The RSW1 and RSW2 dials are already set at 7
and 0.
Setting at the gures from 3 to 9 of the RSW2 dial should not be permitted.
¡ Current Limiter Set Switch = RSW5, 6, 7
RSW5 and RSW6 are used for setting the limiter current value. RSW7 is used for setting activating time of
current limiter.
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