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Unit Controls
PROGRAM KEY
There are six operating parameters under the PROGRAM
key that are programmable. These setpoints can be
changed by pressing the PROGRAM key, and then the
ENTER/ADV key to enter Program Mode . Continuing to
press the ENTER/ADV key will display each operating
parameter. While a particular parameter is being dis-
played, the UP and DOWN arrow keys can be used to
change the value. After the value is changed, the EN-
TER/ADV key must be pressed to enter the data into
memory. Table 14 shows the programmable limits and
default values for each operating parameter.
Following are the displays for the programmable values
in the order they appear:
@ @ @ @ @
D I S C H A R G E
C U T O U T
=
DISCHARGE PRESSURE CUTOUT is the discharge
pressure at which the system will shutdown as moni-
tored by the optional discharge transducer. This is a
software shutdown that acts as a backup for the me-
chanical high pressure switch located in the refrigerant
circuit. The system can restart when the discharge pres-
sure drops 40 PSIG (2.76 BARG) below the cutout point.
If the optional discharge pressure transducer is not in-
stalled, this programmable safety would not apply. It
should be noted that every system has a mechanical
high pressure cutout that protects against excessive high
discharge pressure regardless of whether or not the op-
tional discharge pressure is installed.
S U C T I O N
C U T O U T
=
The SUCTION PRESSURE CUTOUT protects the chiller
from an evaporator freeze-up. If the suction pressure drops
below the cutout point, the system will shut down.
There are some exceptions when the suc-
tion pressure is permitted to temporarily
drop below the cutout point. Details are
explained under the topic of System Safe-
ties.
114
P R E S S U R E
3 9 5
P S I G
P R E S S U R E
4 4 . 0
P S I G
L O W
A M B I E N T
C U T O U T
The LOW AMBIENT TEMP CUTOUT allows the user to
select the chiller outside ambient temperature cutout
point. If the ambient falls below this point, the chiller will
shut down. Restart can occur when temperature rises
2°F (1.11°C) above the cutout setpoint in Table 14.
A N T I
R E C Y C L E
=
6 0 0
The anti-recycle timer message shows the amount of
time left on the respective system's anti-recycle timer.
The programmed ANTI RECYCLE TIME will start to count
down at the start of the system's number one compres-
sor. In effect, this is the minimum time start-to-start on
the respective system's number one compressor.
Another anti-recycle timer is started each time the
system's number one compressor cycles off. This anti-
recycle time is fixed at 120 seconds and starts to count-
down when the system's number 1 compressor cycles off.
The anti-recycle message is displayed when the sys-
tem is unable to start due to either of the anti-recycle
timers being active (counting down). The actual time dis-
played will be the longer of the two timers, start-to-start
or stop-to-start.
F A N
C O N T R O L
P R E S S U R E = X X X P S I G
The Fan Control On Pressure is the programmed pres-
sure value that is used to stage the condenser fans on,
in relation to discharge pressure. Refer to Condenser
Fan Control in the UNIT OPERATION section and Tables
21, 22, and 23, 24. The Fan Control On Pressure is des-
ignated as ctrl_press in the tables.
FA N
D I F F E R E N T I A L
P R E S S U R E = X X X P S I G
The Fan Differential Off Pressure is the programmed dif-
ferential pressure value that is used to stage the con-
denser fans off, in relation to discharge pressure. Refer
to Condenser Fan Control in the UNIT OPERATION sec-
tion and Tables 21, 22, and 23, 24. The Fan Differential
Off Pressure is designated as diff_press in the tables.
T E M P
=
2 5 . 0 ° F
T I M E
S E C
O N
O F F
YORK INTERNATIONAL
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