163
JOHNSON CONTROLS
FORM 201.21-NM4 (616)
163
JOHNSON CONTROLS
6
CHILLER ELECTRONIC COMPONENTS (CON'T)
DC BUS VOLTAGE ISOLATION BOARD
CHILLER CIRCUIT BREAKER
An Optional Circuit Breaker may be supplied on the
input of the system. The incoming power will be fed
to the terminals on the circuit breaker. If the circuit
breaker option is not selected, incoming power will
be fed to terminal blocks. The breaker also provides
ground fault protection. 2 and 3 compressor chillers
utilize one circuit breaker, while 4 compressor chillers
utilize 2 breakers.
LD10620
50082
AUTOTRANSFORMER
LD10624
AUTOTRANSFORMER
The compressor and fan motors are designed to operate
at 460VAC on all voltage units. Whenever a 208VAC 60
Hz, 230VAC 60 Hz, 380VAC 60 Hz, 400VAC 50 Hz, or
575VAC 60 Hz supply is utilized, an autotransformer is
used to convert the voltage to 460VAC. On 50 Hz units,
a frequency converter also converts the fan voltage from
50 Hz to 60 Hz.
The DC Bus Isolation Board allows the VSD Logic
Board to read the voltage on the DC BUS without expos-
ing the VSD Logic Board to the high voltage. Instead,
the DC Bus Isolation Board contains a resistor network
that forms voltage dividers with resistors on the VSD
Logic Board, which steps down the voltages so that
scaled down voltages proportional to the full and 1/2 bus
voltages can be safely fed to the VSD Logic Board. The
DC Bus Isolation Board supplies 3 connections to the
VSD Logic Board; plus bus, minus bus and half bus.
