York YCAS0130 Micro Panel Contents, System Switches 1, Internal Clock & Memory Backup Battery

Micro Panel Contents

1.3 UNIT (CHILLER) ON / OFF SWITCH

A master UNIT (Chiller) ON / OFF switch is located just below the keypad. This switch allows the operator to turn the entire chiller 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 indication will be displayed. See page 122 for the location of this switch.

1.4 MICROPROCESSOR BOARD

The Microprocessor Board controls and makes decisions for the chiller. Information inputs from transducers and sensors around the chiller are either connected directly 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 of these analog inputs, digitizes them, and constantly scans them to monitor chiller operating conditions. Based on this information, the Microprocessor issues commands to the Relay Boards to activate and deactivate contactors, solenoids, etc. for chilled liquid, operating control, and safety control.

Commands are sent from the Microprocessor Board to the I/O Expansion Board to control the slide valves for chilled liquid control.

Keypad commands are acted upon by the micro to change setpoints, cutouts, scheduling, operating requirements, 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 each system are located on the Microprocessor Board (Section 1.11, Item 5). These switches allow the operator to selectively turn a given system on or off as desired.

Internal Clock & Memory Backup Battery

The Microprocessor Board contains a Real Time Clock integrated circuit chip (Section 1.11, Item 2) 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 depend upon whether the Real Time Clock’s internal clock

FORM 201.19-NM1 (204)

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 disabled 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 service. This will not affect the maintenance of programmed values and stored data by the backup battery.

While a chiller is operating, the clock must be ON (Section 1.11, Item 1) or the internal clock on the microprocessor will not be active and the micro cannot keep track of time, although all other functions will operate normally. Failure to turn the Clock ON could result in the chiller not starting due to the time "frozen" on the clock falling outside the Start/Stop time programmed in the Daily Schedule, see Section 7.3.

1.5 ANCILLARY CIRCUIT BOARDS

Power Supply Board

The on-board switching power supply is fuse protected and converts 24VAC from the logic transformer 2T 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 unregulated +24VDC to supply the flow switch, PWM remote temperature reset, PWM remote current reset, lead / lag select, and remote print circuitry which may be utilized with user supplied contacts.

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.

I/O Expansion Board

The I/O Expansion Board provides multiplexing to allow additional 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 Microprocessor through address lines.

Signals routed through the I/O Expansion Board include Discharge Temperature, Motor Protector Current Transformer outputs (motor current signals from the 2ACE Module), and Oil Temperature.

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