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EMS Demand Limiting (Remote Current Reset):
This message indicates the current limiting is in effect
from a Current Limit PWM input. As long as this input is
activated, the micro will not allow loading beyond the
PWM % that has been sent to the Microprocessor
through the PWM input. Generally, this input is used for
purposes of demand limit see Section 1.7.
ISN Demand Limiting:
This message indicates that the chiller is operating un-
der load limiting from an ISN System through the RS-
485 input. This feature controls loading under a num-
ber of ISN programmable values, enhancing the flex-
ibility of controlling the chiller to obtain desired chiller
loading within the overall building control scheme.
Memory Backup Battery Fault:
The Microprocessor Board contains a Real Time Clock
(RTC) I.C. Chip with an internal battery back-up. This
battery back-up assures that any programmed values
(setpoints, etc.), clock, all fault information, and accu-
mulated information such as starts/run time, etc. stored
in the RTC memory is not lost when a power failure
occurs, regardless of length of the power loss.
The battery is a 10 year lithium type. The life of the bat-
tery will depend 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 turned ON and OFF by a jumper on the
Microprocessor Board. While the chiller is operating,
the clock must be ON. Otherwise the internal clock on
the microprocessor will not be active and the micro can
not 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 window
that is programmed in the DAILY SCHEDULE.
If the chiller is shut down for extended periods of months,
it may be desirable to disable the clock to save battery
life. The clock can then be reactivated and repro-
grammed when the chiller is returned to service.
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NOTE: All programmed values and stored data, other
than the internal clock time-keeping, will be
maintained in memory regardless of whether
the clock is on or off and regardless of the length
of the power failure.
To disable the clock, place the jumper (Fig. 38) in the
OFF position. To activate it, place the jumper in the ON
position.
On power-up the microprocessor will check the Real
Time Clock (RTC Chip) battery to assure that the inter-
nal battery is still operational. This is accomplished by
performing an RTC RAM location check. As long as the
battery checks out, the micro will continue on with busi-
ness without interruption.
If a check is made and the battery has failed, the micro-
processor will not allow the chiller to run and the
!!WARNING!! !!LOW BATTERY!! message will appear.
Under low battery conditions, the only way to run the
chiller is to press the MANUAL OVERRIDE key (Sec-
tion 7.4). The MANUAL OVERRIDE key will function
differently than it does in service situations where it over-
rides the daily schedule for only 30 minutes. In a low
battery condition, the MANUAL OVERRIDE key will
zero out the daily schedule to allow unlimited operation
regardless of the time on the internal clock. Default val-
ues will also be loaded into memory for all setpoints
and cut-outs. These may require reprogramming to
assure they meet the chiller operating requirements for
operation board 30 minutes. In addition, the low battery
message which is displayed for this condition will dis-
appear.
NOTE: If a power failure should again occur, the above
process will again need to be repeated to bring
the chiller back on line.
In the unlikely event the low battery message should
ever appear, it will require the RTC chip U13 on the
Microprocessor Board (Fig. 38) to be replaced. Care
should be taken to assure that the chip is properly in-
stalled. Pin 1 (dimple in the top part of the chip) must be
oriented as shown in Fig. 38. The part number of the
RTC Chip is 031-00955-000.
2.3 ANTICIPATION CONTROL STATUS MESSAGES
Anticipation controls are built into the software to pre-
vent safety shutdowns by automatically overriding the
temperature controls if system conditions approach
safety thresholds. This avoids total loss of cooling re-
sulting from a lockout by a safety control.
! ! W A R N I N G ! !
! ! L O W
B A T T E R Y ! !
Содержание Millennium YDAS 410
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