York Millennium YCAJ150 Installation Operation & Maintenance Download

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YORK INTERNATIONAL

To disable the clock, place the jumper (Fig. 26) 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 inter-
nal battery is still operational. This is accomplished by
performing 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 manual
override key will function differently than it normally does
in service situations where it overrides the daily sched-
ule 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
the internal clock. Default values will also be loaded into
memory for all setpoints and cut-outs. These may re-
quire reprogramming to assure they meet chiller operat-

ule to automatically become the lead anytime the se-
lected lead compressor shuts down due to a lockout,
lead system faults and is waiting to restart, lead system
switch on the micro board is in the OFF position, or if a
run permissive is keeping the lead system off. Automatic
switchover in the “MANUAL” mode is provided to try to
maintain chilled liquid temperature as close to setpoint
as possible.

The “dry” contact for manual lead/lag selection is wired
into terminals 13 and 19 on the TB3 Terminal block. The
location of these terminals is shown in Fig. 25.

FIG. 25 – LEAD/LAG CONTACT CONNECTION

LOCATION

LD02093

26001A

FIG. 26 – CLOCK JUMPER

CLOCK JUMPER

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W A R N I N G

! !

L O W

B A T T E R Y

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MEMORY BATTERY BACK-UP

The Microprocessor board contains a Real Time Clock
(RTC) I.C. Chip with an internal battery back-up. The
battery 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 reprogrammed
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.