YORK INTERNATIONAL
108
Panel Temperature Control
Overall control of the chilled liquid temperature is pri-
marily based on the load/balance/unload signals to the
compressor groups by the Mixed Temperature Control
Algorithm described previously. Acting on these sig-
nals, the two compressors in each group are started,
loaded, unloaded, and shut down by the Individual
Panel Algorithm control as described in Section 6.2 for
2 system YCAS chillers. During very low cooling de-
mand and some other conditions, the signals sent to
the individual compressors may be modified by the In-
dividual Panel Algorithms based on the individual
evaporator leaving temperature and the programmed
Panel High and Low Temperature Limits. The actual
action taken on the compressors is modified by the
Panel Algorithms according to the following table:
6.3 CHILLED LIQUID TEMP/RANGE KEY
The Chilled Liquid Temperature / Range key is used to
program the required leaving liquid control temperatures
for the application. When pressed, one of the following
messages will be displayed for 3 seconds:
This message will indicate if the chiller is selected to be
controlled by Local (Control Panel) Setpoint control or
Remote (ISN, Remote PWM Signal, or Remote Con-
trol Center) Setpoint. This is controlled by the S1 Dip
Switch settings on the Microprocessor Board (see Sec-
tion 3.7).
The display will then scroll to one of the following mes-
sages depending on the type of chiller:
YCAS Models:
The display scrolls to a message showing the currently
programmed Control Range (CR) and desired Target
temperature with the cursor below the first digit of the
Control Range Low Limit Water Temperature as shown:
Key in the Low Limit of the Control Range within the
allowed limits. The micro will accept values from 10.0 -
70.0°F. For values below 38°F, Dip Switch S1, Switch
#1 on the Microprocessor Board must be properly pro-
grammed for Brine Cooling (see Section 3.7). If unac-
ceptable values are entered, or the switch is incorrectly
selected when setpoints below 38°F are entered, the
following message will be displayed before returning to
the Control Range message:
After the Low Limit Water Temperature is keyed in, the
cursor will automatically advance to the first digit of the
High Limit Water Temperature value of the Control
Range (CR) as shown:
This value should be programmed for the highest leav-
ing water temperature which is acceptable in the sys-
tem application. A typical value would be 4°F above the
Low Limit Water Temperature and is the default value
programmed into the micro. The micro will accept a
value 1 - 5°F above the Low Limit Water Temperature.
Key in the upper limit High Limit Water Temperature of
the CR and press the Enter key.
The display automatically shows the Target tempera-
ture which is the midpoint of the programmed Control
Range. The Target temperature is the value which the
micro will attempt to control leaving liquid temperature.
NOTE: Failure to press the Enter key will cause the
newly programmed values to be ignored and
not entered into memory.
MIXED TEMP
INDIVIDUAL PANEL
RESULTING
CONTROL
ALGORITHM SIGNAL
ACTION
LOAD
LOAD
LOAD
LOAD
BALANCE
BALANCE
LOAD
UNLOAD
UNLOAD
BALANCE
LOAD
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
UNLOAD
UNLOAD
UNLOAD
LOAD
UNLOAD
UNLOAD
BALANCE
UNLOAD
UNLOAD
UNLOAD
UNLOAD
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
O U T
O F
R A N G E
T R Y
A G A I N !
C R
=
4 2 . 0
T O
4 6 . 0
° F
T A R G E T
=
4 4 . 0
° F
Содержание Millennium YDAS 410
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