York YCAJ44HE8, Installation, Operation And Maintenance Manual

Page: 64 / 92

64 YORK INTERNATIONAL
MEMORY BATTERY BACK-UP
The Microprocessor board contains a Real Time Clock
(RTC) I.C. Chip with an internal battery back-up. The bat-
tery back-up assures that any programmed values,
clock, all fault information, accumulated information
such as starts/run time, etc. stored in the RTC memory
is not lost when a power failure occurs regardless of the
time period.
The battery is a 10-year lithium type. The life of the bat-
tery with power removed will depend upon whether the
Real Time Clock’s internal clock circuit is energized.
With the clock OFF, approximately 10 years can be ex-
pected, with the clock ON, approximately 5 years.
The clock is turned ON and OFF by a jumper on the
Microprocessor Board. While a chiller is operating, the
clock must be ON. Otherwise the internal clock on the
microprocessor will not be active and the micro cannot
keep track of time, although all other functions will oper-
ate normally. This 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.
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. 25) in the
OFF positions. 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 internal
battery is still operational. This is accomplished by per-
forming an RTC RAM location check. As long as the
battery checks out, the microprocessor will continue on
with business without interruption.
If a check is made and the battery has failed, the micro-
processor will not allow the chiller to run and the follow-
ing STATUS message will appear:
The only way to run the chiller is to press the MANUAL
OVERRIDE key. Under low battery conditions, the man-
ual override key will function differently than it normally
does in service situations where it overrides the daily
schedule for only 30 min. In a low battery condition, the
MANUAL OVERRIDE key will zero out the daily sched-
ule to allow unlimited operation regardless of the time on
exceeded. This is done to try to maintain water tempera-
ture as close to setpoint as possible. No lead/lag
switchover will take place if the system switch on the
Microprocessor of the lead compressor is placed in the
OFF position.
The “dry” contact for manual lead/lag selection is wired
into terminals 13 and 19. The location of these contacts
is shown below in Fig. 24.
FIG. 24 – LEAD/LAG CONTACT CONNECTION
LOCATION
LD02179
CLOCK JUMPER
FIG. 25 – CLOCK JUMPER
26001A
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