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PWM remote temperature reset, and demand limit cir-
cuitry which is available to be used with field supplied
contacts.
The Microprocessor Board energizes on-board relays
to output 120 VAC to motor contactors, solenoid valves,
etc. to control system operation.
UNIT SWITCH
A UNIT ON/OFF switch is just underneath the keypad.
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 param-
eters 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.
YORK INTERNATIONAL
KEYPAD
The 12 button non-tactile keypad allows the user to re-
trieve vitals system parameters such as system pres-
sures, temperatures, compressor running times and
starts, option information on the chiller, and system
setpoints. This data is useful for monitoring chiller op-
eration, diagnosing potential problems, troubleshooting,
and commissioning the chiller.
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 avail-
able.
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 limiting
and anti-recycle/coincident timer status. The display 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 Sta-
tus.
FORM 150.62-NM2
2
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