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1. INTRODUCTION & PHYSICAL DESCRIPTION
1.1 SYSTEM SWITCHES 1 - 2
System switches for each refrigerant system are lo-
cated on the AMB board. These switches allow the
operator to selectively turn a given system 'ON' or 'OFF'
as required.
1.2 INTERNAL CLOCK & MEMORY BACKUP
BATTERY
The AMB board contains a real time clock (RTC) inte-
grated circuit chip with an internal battery backup. The
battery backup assures that any programmed values
(setpoints, clock, cutouts, etc.) are not lost during a
power failure or shutdown period regardless of the time
involved.
The battery is a 10 year lithium type, but life will de-
pend upon whether the RTC internal clock circuit is
energized. With the clock 'OFF', a rated life of approxi-
mately 10 years can be expected. With the clock 'ON',
approximately 5 years. The clock is enabled and dis-
abled using a jumper on the AMB board.
If the chiller is shutdown or power failure is expected
for extended periods, it may be desirable to disable the
clock to save battery life. The clock can then be reacti-
vated and reprogrammed when the chiller is returned
to service. This will not affect the maintenance of pro-
grammed values and stored data by the backup battery.
While a chiller is operating, the clock must be 'ON' or
the internal clock on the microprocessor will not be
active and the microprocessor cannot keep track of time,
although all other functions will operate normally. Fail-
ure to turn the Clock 'ON' could result in the chiller
not starting due to the time "frozen" on the clock fall-
ing outside the start/stop time programmed in the
'DAILY SCHEDULE'.
1.3 POWER SUPPLY BOARD (APB)
The onboard switching power supply is fuse protected
and converts 24VAC from the logic transformer 2T to
+12VDC REG which is supplied to the AMB board,
ARB boards, and the 40 character display to operate the
integrated circuitry. The 24VAC is filtered, but not regu-
lated, to provide unregulated + 24VDC to supply the
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SECTION 7
MICROPANEL
flow switch, PWM remote temperature reset, PWM re-
mote current reset, lead/lag select, and remote print cir-
cuitry which may be utilized with user supplied contacts.
The 24VAC is also filtered and regulated to +24VDC
to be used by the optional EMS/BAS circuit boards for
remote temperature or remote current reset.
1.4 INPUT/OUTPUT EXPANSION BOARD (AIOB)
The AIOB boards provide multiplexing to allow addi-
tional inputs to be connected to the AMB board via a
single data line. The additional inputs are multiplexed
according to the selection made by the microprocessor
through address lines.
Signals routed through the AIOB board are Discharge,
Oil and Cooler Inlet Refrigerant temperatures. Signals
from the motor protector modules representing motor
current are also routed through the AIOB board.
Included on the AIOB boards are the outputs for the
slide valve control. This control consists of a Digital to
Analogue Converter (DAC) and power transistors to
modulate current through the slide valve solenoids.
Power to drive the slide valves is taken from Trans-
former T3.
1.5 RELAY OUTPUT BOARD (ARB)
The ARB boards operate the motor contactors / start-
ers, solenoid valves, and heaters which control system
operation.
The relay boards are located in the logic section of the
control panel. The boards convert 0 - 12VDC logic out-
puts from the AMB board to 115VAC used by the
contactors, valves, etc.
The common side of all relays on the ARB board is
connected to +12VDC REG. The open collector out-
puts of the AMB board energize the DC relays by pull-
ing the other side of the relay coil to 0VDC. When not
energized, both sides of the relay coils or triacs will be
at +12VDC potential.
FORM 201.25-NM1 (302)
7
33
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