York YLUA0248 Series Installation Operation & Maintenance page 114

SECTION 7 – UNIT CONTROLS
software shutdown that acts as a backup for the me-
chanical high pressure switch located in the refriger-
ant circuit. The system can restart when the discharge
pressure 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 optional discharge pressure is installed.
S U C T I O N
C U T O U T =
The SUCTION PRESSURE CUTOUT protects the
unit from a coil freeze-up or compressor damage. If
the suction pressure drops below the cutout point, the
system will shut down.
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 unit outside ambient temperature cut-
out point. If the ambient falls below this point, the unit
will shut down. Restart can occur when temperature
rises 2°F (1.11°C) above the cutout setpoint.
A N T I R E C Y C L E
= 6 0 0
The programmable anti-recycle timer assures that
systems do not cycle. This timer is programmable un-
der the PROGRAM key between 300 - 600 seconds.
Whenever possible, to reduce cycling and motor heat-
ing, the anti-recycle timer should be adjusted as high as
possible. The programmable 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 permitted 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 maximum.
114
P R E S S U R E
8 0 . 0 P S I G
T E M P
= 2 5 . 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 = 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. See Condenser Fan
Control in SECTION 8 – UNIT OPERATION and Ta-
ble 20 on page 130, Table 21 on page 131, and Table
22 on page 132.
The microprocessor will not allow
programming the "FAN CONTROL
ON PRESSURE" minus the "FAN
CONTROL DIFFERENTIAL OFF
PRESSURE" below 160PSIG. This
assures discharge pressure does not
drop too low.
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 con-
denser fans off, in relation to discharge pressure. Refer
to Condenser Fan Control in SECTION 8 – UNIT OP-
ERATION and Tables 18 - 24.
The microprocessor will not allow
programming the "FAN CONTROL
ON PRESSURE" minus the "FAN
CONTROL DIFFERENTIAL OFF
PRESSURE" below 160 PSIG. This
assures discharge pressure does not
drop too low.
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 are the
amount of compressors in the unit, and determines the
stages of cooling available. Notice in Table 15 that
the selection available will vary depending on the unit
model.
This MUST be programmed correctly
to assure proper condensing unit
operation.
FORM 150.73-NM2
ISSUE DATE: 09/07/2020
O N
O F F
X X X P S I G
O F
= 6
JOHNSON CONTROLS