York YCAL0019 Installation, Operation And Maintenance Manual page 162

SECTION 7 – UNIT CONTROLS
S Y S X S P
D P
These displays show suction and discharge pressures
for each system. The discharge pressure transducer is
optional on some models.
If the optional discharge transducer is not installed, the
discharge pressure would display 0 PSIG (0 barg).
The minimum limits for the display are:
• Suction Pressure: 0 PSIG (0 barg)
• Discharge Pressure: 0 PSIG (0 barg)
The maximum limits for the display are:
• Suction Pressure: 400 PSIG (27.58 barg)
• Discharge Pressure: 650 PSIG (44.82 barg)
S Y S X H O U R S
2 = X X X X X,
S Y S X S T A R T S
2 = X X X X X,
The above two messages will appear sequentially for
each system. The first display shows accumulated run-
ning hours of each compressor for the specific system.
The second message shows the number of starts for
each compressor on each system.
Run times and starts will only be
displayed for the actual number of
systems and compressors on the unit.
A total of 99,999 hours and starts can be logged before
the counter rolls over to "0".
L O A D T I M E R
U N L O A D T I M E R
This display of the load and unload timers indicate
the time in seconds until the unit can load or unload.
Whether the systems loads or unloads is determined by
how far the actual liquid temperature is from setpoint.
A detailed description of unit loading and unloading is
covered under the topic of "Capacity Control" located
in Section 8, Unit Operation.
162
= 7 2 . 1 P S I G
= 2 2 7 . 0 P S I G
1 = X X X X X
3 = X X X X X
1 = X X X X X
3 = X X X X X
5 8 S E C
0 S E C
C O O L I N G
2 O F
The display of COOLING DEMAND indicates the
current "step" in the capacity control scheme when in
Return Water Control Mode. The number of available
steps are determined by how many compressors are in
the unit. In the above display, the "2" does not mean
that two compressor are running but only indicates that
the capacity control scheme is on step 2 of 8. Capacity
Control is covered in more detail in this publication
which provides specific information on compressor
staging (for Return Water Control only).
T E M P E R R O R
T E M P R A T E
The COOLING DEMAND message will be replaced
with this message when Leaving Chilled Liquid Control
is selected. This message indicates the temperature error
and the rate of change of the chilled liquid temperature.
L E A D S Y S T E M
S Y S T E M
This display indicates the current LEAD system. In this
example system 2 is the LEAD system, making system
1 the LAG system. The LEAD system can be manually
selected or automatic. Refer to the programming under
the OPTIONS key. The Lead System display will only
appear on a two system unit.
A unit utilizing hot gas bypass should
be programmed for MANUAL with
system 1 as the lead system. Failure
to do so will prevent hot gas operation
if system 2 switches to the lead system
when programmed for AUTOMATIC
LEAD/LAG.
E V A P O R A T O R
S T A T U S I S
This display indicates the status of the evaporator
heater. The evaporator heater is controlled by ambient
air temperature. When the ambient temperature drops
below 40 °F the heater is turned ON. When the tem-
perature rises above 45 °F the heater is turned OFF. An
under voltage condition will keep the heater OFF until
full voltage is restored to the system.
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
D E M A N D
8 S T E P S
X X X . X ° F
X X X . X ° F / M
I S
N U M B E R 2
H E A T E R
= X X X
JOHNSON CONTROLS