Figure 2 - Chiller Control System - York YVAA Installation Operation & Maintenance

SECTION 2 - PRODUCT DESCRIPTION
Inputs
Pressure transducers
Temperature sensors
Switches
Liquid flow
High pressure
Start / stop
Level
Customer supplied
contacts
Communications
Building automation
printer modem
3 phase power line
Rectifier
Signal From Main Control Panel

Figure 2 - Chiller control system

Oil separators utilize no moving parts. Oil cooling is
accomplished by refrigerant leaving the eductor flash-
ing in the suction line which cools the oil, motor, and
compressor.
An integral liquid cooled, transistorized, PWM,
Variable Speed Drive (VSD) is controlled by the
chiller microprocessor control panel to start/stop, select
compressors to run, and select compressor speed.
Displacement Power Factor is 0. 95 at part or full load.
16
Control panel
Chiller control
Microprocessor
user interface
display and
Display
AC/DC Rectifier
Rectifier Controller
SCR Trigger Board
VSD Logic Board
board
keypad
Keypad
Power Driver
(IGBT)
IGBT Gate Driver
PWM Signal
The chiller microprocessor communicates with the
VSD Logic Board using a 3-wire RS-485 opto cou-
pled data link. The VSD Logic Board runs the num-
ber of compressors required to meet the load and the
compressors to the speed requested by the chiller mi-
croprocessor.
The basic system control and VSD system
architecture is shown in Figure 2 on page 16.
Form 201.47-ICOM1
Issue date: 17/11/2022
Outputs
Relay output board
Solenoids
Contactors
Alarm
Pump
Compressor heater
Run status
Evaporator heater
VSD
VSD logic board
SCR trigger board
Power components
PWM (speed control)
Motor
LD15028
Compressor 1
Compressor 2
Inverter
LD15158
JOHNSON CONTROLS