JOHNSON CONTROLS
76
FORM 150.62-NM6 (103)
This safety can be triggered by two events. The rst is
when suction superheat <2.0°F for 3 seconds. The second
is when the EEV pilot solenoid is closed 10 times in 2
minutes due to low superheat.
The Sensor Failure Safety prevents the system from
running when the sensors measuring superheat are not
functioning properly. This safety is only active when EEV
is selected as the expansion valve type in SERVICE
Mode. This safety is ignored for the rst 15 seconds of
system runtime.
This safety will shut down a system if either suction
temperature or suction pressure sensors read out of
range high or low. This condition must be present for
3 seconds to cause a system shutdown. The safety
locks out a system after the rst fault and will not allow
automatic restarting.
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.
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.
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 ow conditions or
if the micro panel setpoint values are improperly pro-
grammed. Anytime the leaving chilled liquid temperature
(water or glycol) drops below the cutout point, the chiller
will shutdown. Restart can occur when chilled liquid tem-
perature rises 2°F above the cutout.
The Under Voltage Safety assures that the system is
not operated at voltages where malfunction of the mi-
croprocessor could result in system damage. When the
115VAC 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 nished counting down.
When the CURRENT FEEDBACK ONE PER UNIT op-
tion is selected under the OPTIONS Key, the unit will
shut down when the voltage exceeds the programmed
trip voltage for 5 seconds.
The trip voltage is programmed at the factory according
to compressor or unit RLA.
Restart will occur after the anti-recycle timer times
out.
UNIT WARNING
The following messages are not unit safeties and will
not be logged to the history buffer. They are unit warn-
ings and will not auto-restart. Operator intervention is
required to allow a restart of the chiller.
The Low Battery Warning can only occur at unit
power-up. On micro panel power-up, the RTC battery
is checked. If a low battery is found, all programmed
setpoints, program values, options, time, schedule, and
history buffers will be lost. These values will all be reset
to their default values which may not be the desired oper-
ating values. Once a faulty battery is detected, the unit
will be prevented from running until the PROGRAM key
is pressed. Once PROGRAM is pressed the anti-recycle
timers will be set to the programmed anti-recycle time to
allow the operator time to check setpoints, and if neces-
sary, reprogram programmable values and options.
If a low battery is detected, it should be replaced as
soon as possible. The programmed values will all be
lost and the unit will be prevented from running on the
next power interruption. The RTC/battery is located at
U17 on the microboard.
U N I T F A U L T :
L O W A M B I E N T T E M P
U N I T F A U L T :
1 1 5 V A C U N D E R V O L T A G E
U N I T F A U L T :
L O W L I Q U I D T E M P
! ! L O W B A T T E R Y ! !
C H E C K P R O G / S E T P / O P T N
Unit Controls
U N I T F A U L T :
H I G H M T R C U R R
S Y S 1 S E N S O R F A I L U R E
S Y S 2 S E N S O R F A I L U R E
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