York YCAL0019 Installation, Operation And Maintenance Manual page 174

SECTION 7 – UNIT CONTROLS
There are some exceptions when the
suction pressure is permitted to tem-
porarily drop below the cutout point.
Details are explained under the topic
of System Safeties.
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.
L E A V I N G L I Q U I D
C U T O U T
The LEAVING LIQUID TEMP CUTOUT protects the
chiller from an evaporator freeze-up. Anytime the leav-
ing chilled liquid temperature drops to the cutout point,
the chiller shuts down. Restart will be permitted when
the leaving chilled liquid temperature rises 2 °F (1.11
°C) above the cutout setpoint.
When water cooling mode is programmed (OPTIONS
key), the value is fixed at 36.0 °F (2.22 °C) and cannot
be changed. Glycol cooling mode can be programmed
to values listed in Table 13.
A N T I R E C Y C L E
= 6 0 0
The programmable anti-recycle timer assures that
systems do not short cycle, and the compressor mo-
tors have sufficient time to dissipate heat after a start.
This timer is programmable under the PROGRAM key
between 300 and 600 seconds. Whenever possible,
to reduce cycling and motor heating, the anti-recycle
timer should be adjusted as high as possible. The pro-
grammable anti-recycle timer starts the timer when the
first compressor in a system starts. The timer begins to
count down. If all the compressors in the circuit cycle
OFF, a compressor within the circuit will not be per-
mitted to start until the anti-recycle timer has timed
out. If the lead system has run for less than 5 minutes,
3 times in a row, the anti-recycle timer will be extended
to 10 minutes, if currently programmed for less than 10
minutes.
174
T E M P
= 2 5 . 0 ° F
T E M P
= 3 6 . 0 ° F
T I M E R
S E C
F A N C O N T R O L
P R E S S U R E
The FAN CONTROL ON-PRESSURE is the pro-
grammed pressure value that is used to stage the con-
denser fans ON, in relation to discharge pressure. Refer
to Condenser Fan Control in the UNIT OPERATION
section and Tables 19, 20, 21 and 22.
F A N D I F F E R E N T I A L
P R E S S U R E =
The FAN DIFFERENTIAL OFF PRESSURE is the
programmed differential pressure value that is used to
stage the condenser fans OFF, in relation to discharge
pressure. Refer to Condenser Fan Control in the UNIT
OPERATION section and Tables 19, 20, 21 and 22.
T O T A L N U M B E R
C O M P R E S S O R S
The TOTAL NUMBER OF COMPRESSORS is the
total quantity of compressors in the chiller, and deter-
mines the stages of cooling available. Note in Table
13, the chiller may have single or dual systems. Single
system units can have 2 or 3 compressors, while dual
system units may have 4 or 6 compressors.
This MUST be programmed correctly
to assure proper chiller operation.
A single system chiller MUST have a
jumper between terminals J9-7 and
+24V on the I/O board. This connec-
tion can be made between terminals 13
and 17 on terminal block CTB1. If the
jumper is not installed, the unit will
act as a 2-system chiller. The jumper
is only checked by the microproces-
sor at unit power-up. If the jumper
is removed, power must be removed
and re-applied to register the change
in memory.
This MUST be programmed correctly
to assure proper chiller operation.
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
O N
= X X X P S I G
O F F
X X X P S I G
O F
= 6
JOHNSON CONTROLS