York YCUL0020 Installation, Operation And Maintenance Manual page 118

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).
Some models come factory wired with a low pressure
switch in place of the suction transducer. In this case,
the suction pressure would only be displayed as the
maximum suction pressure reading of greater than 400
psig (27.6 barg) when closed, or less than 0 psig (0
barg) when open.
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 (27.6 barg)
Discharge Pressure: 650 psig (44.8 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".
118
= 1 1 5 . 1 P S I G
= 3 O 5 . 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
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.
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. See the programming
under the Options Key on page 133. 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 pro-
grammed for AUTOMATIC LEAD/LAG.
E V A P P U M P
E V A P H E A T E R
This display is for chiller applications only and does
not apply to condensing units. However, the evaporator
contacts could be used to control the air handler.
The evaporator pump dry contacts are energized
(closed) when any compressor is running, or the unit
is not OFF on the daily schedule and the unit switch is
ON. However, even if one of above is true, the contacts
will not close if the micro panel has been powered up
for less than 30 seconds or if the contacts have been
closed in the last 30 seconds.
Form 150.63-NM9
Issue date: 5/20/2021
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JOHNSON CONTROLS