York MILLENNIUM YCUL0016SC, Assembly, Installation, Operation & Maintenance

Page: 97 / 172

YORK INTERNATIONAL
FORM 150.63-NM1
97
3
24VAC is rectified and filtered to provide unregulated
+30 VDC to supply the flow switch, PWM remote tem-
perature reset, and demand limit circuitry which is avail-
able to be used with field supplied contacts.
The Microprocessor Board energizes on-board relays
to output 120 VAC to motor contactors and solenoid
valves to control system operation.
UNIT SWITCH
A UNIT ON/OFF switch is just underneath the key-
pad. This switch allows the operator to turn the entire
unit OFF if desired. The switch must be placed in the
ON position for the chiller to operate.
DISPLAY
The 40 Character Display (2 lines of 20 characters) is a
liquid crystal display used for displaying system pa-
rameters and operator messages.
The display in conjunction with the keypad, allows the
operator to display system operating parameters as well
as access programmed information already in memory.
The display has a lighted background for night viewing
and for viewing in direct sunlight.
When a key is pressed, such as the OPER DATA key,
system parameters will be displayed and will remain
on the display until another key is pressed. The system
parameters can be scrolled with the use of the up and
down arrow keys. The display will update all informa-
tion at a rate of about 2 seconds.
Display Messages may show characters indicating
“greater than” (>) or “less than” (<). These characters
indicate the actual values are greater than or less than
the limit values which are being displayed.
KEYPAD
The 12 button non-tactile keypad allows the user to re-
trieve vital system parameters such as system pressures,
temperatures, compressor running times and starts, op-
tion information on the unit, and system setpoints. This
data is useful for monitoring unit operation, diagnos-
ing potential problems, troubleshooting, and commis-
sioning the unit.
It is essential the user become familiar with the use
of the keypad and display. This will allow the user to
make full use of the capabilities and diagnostic features
available.
BATTERY BACK-UP
The Microprocessor Board contains a Real Time Clock
integrated circuit chip with an internal battery back-up.
The purpose of this battery back-up is to assure any
programmed values (setpoints, clock, cutouts, etc.) are
not lost during a power failure regardless of the time
involved in a power cut or shutdown period.
UNIT STATUS
Pressing the STATUS key will enable the operator to
determine current chiller operating status. The messages
displayed will include running status, cooling demand,
fault status, external cycling device status, load limit-
ing and anti-recycle/coincident timer status. The dis-
play will be a single message relating to the highest
priority message as determined by the micro. Status
messages fall into the categories of General Status and
Fault Status.