York YLAA0041 Installation Operation & Maintenance page 139

Form 150.72-ICOM6
Issue date: 12/19/2023
Unit Safeties
Unit safeties are faults that cause all running compres-
sors to be shut down. Unit faults are auto reset faults
in that the unit will be allowed to restart automatically
after the fault condition is no longer present.
U N I T
L O W A M B I E N T
The Low Ambient Temp Cutout is a safety shutdown
designed to protect the chiller from operating in a low
ambient condition. If the outdoor ambient temperature
falls below the programmable cutout, the chiller will
shut down. Restart can occur when temperature rises
2°F above the cutoff.
U N I T F A U L T :
L O W L I Q U I D
The Low Leaving Chilled Liquid Temp Cutout protects
the chiller form an evaporator freeze-up should the
chilled liquid temperature drop below the freeze point.
This situation could occur under low flow conditions or
if the micro panel set point values are improperly pro-
grammed. Anytime the leaving chilled liquid tempera-
ture (water or glycol) drops below the cutout point, the
chiller will shutdown. Restart can occur when chilled
liquid temperature rises 2°F above the cutout.
U N I T F A U L T :
C H E C K L I Q
If the leaving chilled liquid temperature rises over
2.0°F above the entering chilled liquid temperature for
60 continuous seconds, the chiller shuts down. This
fault activates when the unit is running, and the control
panel is programmed for leaving chiller liquid temper-
ature control. If the Entering Chilled Liquid Tempera-
ture Sensor is disabled under Unit Setup, this fault is
disabled. This fault requires a manual reset to restart
the unit.
U N I T F A U L T :
P U M P
On units with one pump: This indicates that the
manual motor starter protecting the pump from short
circuit or overload conditions has tripped or been
set to OFF. Setting the device to ON resets the trip.
On units with two pumps, duty and standby: This indi-
cates that both the manual motor starters protecting the
pumps from short circuit or overload conditions have
Johnson Controls
F A U L T :
T E M P
T E M P
T E M P S E N S
T R I P
tripped or both have been set to OFF. Setting at least
one of the devices to ON resets the trip.
U N I T F A U L T :
P U M P F A I L
On units with one pump: After the 30 second stop
to start timer has timed out, the pump is starterd if
there is a Leaving Liquid Temperature Cutout, or
any of the compressors are running, or with the dai-
ly schedule not calling for a shutdown with the unit
switch on and the remote stop/start input closed. If
the flow switch does not close within 10 seconds,
the unit locks out on UNIT FAULT: PUMP FAIL
MAKE FLOW and the pump is stopped. Setting the
unit switch to OFF then back to ON resets the trip.
On units with two pumps, duty and standby: After the
30 second stopto start timer has times out, the pump is
started if there is a Leaving Liquid Temperature Cut-
out, or any of the compressors are running, or with
the daily schedule not calling for a shutdown with the
unit switch on and the remote stop/start input closed.
If the flow switch does not close within 10 seconds
the running pump is stopped and the standby pump is
started. If in a further 10 seconds the flow switch does
not close the unit locks out on UNIT FAULT: PUMP
FAIL MAKE FLOW and the running pump is stopped.
Setting the unit switch to OFF, then back to ON resets
the trip. In attempting to clear this fault check that one
of the manual motor starters protecting the pumps has
not tripped.
U N I T
1 1 5 V A C U N D E R
The Under Voltage Safety ensures that the system is
not operated at voltages where malfunction of the mi-
croprocessor could result in system damage. When
the 115 VAC to the micro panel drops below a certain
level, a unit fault is initiated to safely shut down the
unit. Restart is allowed after the unit is fully powered
again and the anti-recycle timers have finished count-
ing down.
U N I T
H I G H M T R
When the CURRENT FEEDBACK ONE PER UNIT
option is selected under the OPTIONS key, the unit will
shut down when the voltage exceeds the programmed
trip voltage for 5 seconds.
Section 7: Unit controls
M A K E F L O W
F A U L T :
V O L T A G E
F A U L T :
C U R R
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