York YLUA0248 Series, Installation Operation & Maintenance

Page: 103 / 158

JOHNSON CONTROLS
103
SECTION 7 – UNIT CONTROLS
FORM 150.73-NM2
ISSUE DATE: 09/07/2020
7
S Y S X S P = 7 2 . 1 P S I G
D P = 2 2 7 . 0 P S I G
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 pres-
sure switch in place of the suction transducer. In this
case, the suction pressure would only be displayed as
the maximum suction pressure reading of >200 PSIG
(13.79 barg) when closed, or < 0 PSIG (0 barg) when
open.
The m inimum 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 1 = X X X X X
2 = X X X X X, 3 = X X X X X
S Y S X S T A R T S 1 = X X X X X
2 = X X X X X, 3 = 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 dis-
played 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 5 8 S E C
U N L O A D T I M E R 0 S E C
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 I S
S Y S T E M N U M B E R 2
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 P U M P I S O N
E V A P H E A T E R I S O F F
This display is for chiller applications only and does
not apply to condensing units. However, the evapora-
tor 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.