York YLUA0248 Series, Installation Operation & Maintenance

Page: 96 / 158

JOHNSON CONTROLS
96
FORM 150.73-NM2
ISSUE DATE: 09/07/2020
SECTION 7 – UNIT CONTROLS
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 unit 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
information at a rate of about 1 a second.
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
retrieve 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, troubleshoot-
ing, 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 available.
BATTERY BACK-UP
The Microprocessor Board contains a Real Time Clock
integrated circuit chip with an internal battery backup.
The purpose of this battery backup 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.
TRANSFORMER
A 40 VA, 120/24VAC 50/60Hz transformer is provided
to supply power to the Microprocessor Board, which
in turn rectifies, filters, and regulates as necessary to
supply power to the display, sensors, and transducers.
SINGLE SYSTEM SELECT AND
PROGRAMMING NUMBER OF
COMPRESSORS
The control software is common between single (1)
and dual (2) system units. A jumper is installed be-
tween terminals 13 and 17 on the user terminal block
to configure a unit for a single system. Dual (2) sys-
tem units do not have a jumper installed. The jumper is
only checked by the micro on power-up.
The total number of compressors is programmable un-
der the Program Key. Single (1) system units can have
2 or 3 compressors. Dual (2) system units can have 4,
5, or 6 compressors.