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1.3 UNIT (CHILLER) ON (AUTO) / OFF SWITCH
A Master UNIT (Chiller) ON (Auto) / OFF switch is lo-
cated just below the keypad. This switch allows the
operator to turn the entire chilled OFF if desired. The
switch must be placed in the ON position for the chiller
to operate. Any time the switch is in the OFF position, a
Status message indicating this is displayed. See Page
16 for the location of this switch.
1.4 MICROPROCESSOR BOARD(S)
The Microprocessor Board(s) controls and makes deci-
sions for the chiller. Information inputs from transducers
and sensors around the chiller are either connected di-
rectly to the Microprocessor Board or are connected to
the I/O Expansion Board and multiplexed before being
sent to the Microprocessor Board. The Microprocessor
Board circuitry multiplexes all these analog inputs, digi-
tizes them, and constantly scans them to monitor chiller
operating conditions. Based on this information, the Mi-
croprocessor issues commands to the Relay Boards to
activate and deactivate contactors, solenoids, etc. for
chilled liquid control and safety control.
Keypad commands are acted upon by the micro to
change setpoints, cutouts, scheduling, operating re-
quirements, and to provide displays.
A +12VDC REG supply voltage from the Power Supply
Board is converted to +5V REG by a voltage regulator
located on the Microprocessor Board. This voltage is
used to operate the integrated circuitry on the board.
System Switches 1 - 4
System Switches for up to four systems are located on
the Microprocessor Board (Section 1.8, Item 5). These
switches allow the operator to selectively turn a given
system on or off as desired. On models fitted with a
Master and
Subordinate
Control Panels, system 3 & 4,
can be
controlled using the system switches on the
Master and
Subordinate
Microprocessor boards.
Internal Clock & Memory Backup Battery
The Microprocessor Board contains a Real Time Clock
integrated circuit chip (Section 1.8, Item 2) with an in-
ternal 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 its life will de-
pend upon whether the Real Time Clocks internal clock
circuit is energized. With the clock Off, a rated life of
approximately 10 years can be expected. With the clock
On, approximately 5 years. The clock is enabled and dis-
abled using a jumper on the Microprocessor Board.
If the chiller is shut down 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 reactivated
and reprogrammed when the chiller is returned to ser-
vice. This will not affect the maintenance of programmed
values and stored data by the backup battery.
While the chiller is operating, the clock must be On (Sec-
tion 1.8, Item 1) or the internal clock on the micropro-
cessor will not be active and the micro cannot keep track
of time, although all other functions will operate normally.
Failure to turn clock On could result in the chiller not
starting due to the time frozen on the clock falling out-
side the Start/Stop time programmed in the Daily Sched-
ule, see Section 7.3. Also, on master/
subordinate
chillers (3 &
4 compressor models), be sure that both
micropanels
have the CLOCK jumper in the same
position.
EPROM
An EPROM is installed in the microprocessor board(s).
The EPROM holds the program which controls all chiller
action. On 3 and 4 compressor chillers, identical part #
EPROMs are installed. To enable the EPROMs pro-
gram to know which panel is to be the MASTER and
SUBORDINATE
, a wire is factory installed between
J4-3 of the
microprocessor board and Terminal 13 of
TB4.
1.5 ANCILLARY CIRCUIT BOARDS
Power Supply Board
The on-board switching power supply is fuse protected
and converts 24VAC from the logic transformer to +12V
REG which is supplied to the Microprocessor Board,
Relay Output Boards, and the 40 character display to
operate the integrated circuitry.
24VAC is filtered, but not regulated, to provide unregu-
lated +24VDC to supply the flow switch, PWM remote
temperature reset, PWM remote current reset, lead /
lag select, and remote print circuitry which may be uti-
lized with user supplied contacts.
24VAC is also filtered and regulated to +24VDC to be
used by the optional EMS/BAS Circuit Boards for re-
mote temperature or remote current reset.
Individual recitifier and filtering circuits are present which
receive the Current Transformer signals for each phase
of motor current on each compressor. These circuits
rectify and filter the signals to variable DC. A phase ro-
tation circuit for each compressor is also present to as-
sure that the screw compressors do not run in the wrong
direction. All of these signals are sent to the I/O Expan-
sion Board which multiplexes them and then feeds them
to the Microprocessor Board.
I/O Expansion Board
The I/O Expansion Board is a multiplexer allowing ad-
ditional inputs to be connected to the Microprocessor
Board via a single data line. The additional inputs are
multiplexed according to the selection made by the Mi-
croprocessor by means of address lines.
Содержание Millennium YDAS 410
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