York Millennium YCAS 316, Installation Operation & Maintenance, Page: 97 / 144

FORM 201.10-NM1
97
YORK INTERNATIONAL
SETPOINT KEYS
GENERAL
The microprocessor utilizes leaving chilled liquid control
to maintain chilled liquid temperature within the pro-
grammed CONTROL RANGE (CR). Regulating leaving
chilled liquid temperature within the CR is accomplished
through capacity control of the compressor’s slide valve.
A series of load and unload pulses are sent to the com-
pressor slide valve to maintain LWT within a desired
range. Attention is also provided by the micro to maxi-
mize efficiency and minimize compressor cycling. The
control algorithm in the micro combines control zones
and internal timers to maintain chilled liquid temperatures
and minimize cycling of the two compressors. This
method of control is suitable for both water and brine
cooling. Control setpoints (CONTROL RANGE) are pro-
grammed into the panel to establish the desired range of
leaving chilled operating temperatures. A description of
the operation and programming follows.
PROGRAMMING CHILLED LIQUID TEMP / RANGE
Chilled Liquid/Temp Range
When the CHILLED LIQUID TEMP / RANGE key is
pressed, one of the following messages will be displayed
for 3 seconds:
This message will inform the user that the chiller is se-
lected to be controlled by a LOCAL (Control Panel)
Setpoint control or REMOTE (FAX 4500, Remote PWM
Signal, or Remote Control Center) Setpoint control.
Selection is made on the S1 Dip Switch on the Micropro-
cessor Board (Page 80). Normally, unless a FAX 4500,
Remote PWM Signal or Remote Control Center is con-
nected to the Micropanel, the Local Mode will be se-
lected.
The display will then scroll to a second message which
will display the desired CONTROL RANGE (CR) and the
“TARGET” temperature.
The CONTROL RANGE (CR) is the programmed varia-
tion in leaving chilled liquid temperature which is accept-
able to the user for the system application. The example
CHILLED LIQUID/
TEMP RANGE
L O C A L
W A T E R T E M P C O N T R O L
R E M O T E
W A T E R T E M P C O N T R O L
C R = 4 2 . 0 T O 4 6 . 0 ° F
T A R G E T = 4 4 . 0 ° F
FIG. 27 – SETPOINT KEYS
28164A
SETPOINT
KEYS