212
JOHNSON CONTROLS
FORM 201.21-NM4 (1020)
212
JOHNSON CONTROLS
MICRO PANEL
UNIT SAFETIES
Unit Safety Operation
Unit faults are safeties that cause all running compres-
sors to be shut down, if a safety threshold is exceeded
for 3 seconds. Unit faults are recorded in the history
buffer along with all data on the unit and system operat
-
ing conditions. Unit faults are auto reset faults where
the unit will be allowed to restart automatically after the
fault condition is no longer present. The only exception
is any of the VSD related unit faults. If any 3 VSD unit
faults occur within 90 minutes, the unit will be locked
out on the last fault. A VSD lockout condition requires
a manual reset using the system switches. Both system
switches must be cycled off and on to clear a VSD unit
lockout fault. If a unit safety is in effect, the message
will be displayed to the operator when the Status key
is pressed.
In the descriptions of the fault displays that follow, the
fault message will show a YYYYYYY to indicate that a
system is in a “FAULT” condition and will restart when
the fault clears or LOCKOUT” and will not restart until
the operator clears the fault using the keypad.
If a control panel safety occurs after the VSD fault,
but before the fault is reset, the control panel fault is
an ALL FAULT of the VSD fault, meaning it will be
registered as such in the History because it occurred
while the VSD was shutting down or while the systems
were shut down. All faults do not store operating data
at the time of the fault.
LD10605
STATUS
KEY
If a “VSD” fault occurs during the fault rampdown or
while the systems are shut down, the VSD fault will be
registered as a new fault. The reason for this is the belief
any VSD fault should be registered with a full account
of the systems data at the time of the fault.
High Ambient Temp Fault
If the ambient temperature rises above 130 F, the chiller
will shut down with a controlled ramped shutdown. Re-
start will automatically occur, if demand allows, when
temperature falls 2°F below the cutout (128°F). This
fault cannot cause a lockout. The fault display message
will be present only during the time when the ambient
temperature is causing a fault condition. A sample dis-
play is shown below:
The unit will also be inhibited from starting any time
the temperature is above 128°F.
Low Ambient Temp Fault
If the ambient temperature falls below the programmable
Low Ambient Temp Cutout the chiller will shut down
with a controlled ramped shutdown. This fault will only
occur if the Low Ambient Cutout is “ENABLED” under
the OPTIONS key. Restart can occur, if demand allows,
when temperature rises 2°F above the cutout. This fault
cannot cause a lockout. The fault display message will
be present only during the time when the ambient tem-
perature is causing a fault condition. A sample display
is shown below:
UNIT YYYYYYYY
HIGH AMBIENT TEMP
UNIT YYYYYYYY
LOW AMBIENT TEMP
The unit is also inhibited from starting any time the
temperature is below the 2°F.
