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MICRO PANEL
System Safety (Fault) Operation
System safeties are faults that cause individual systems
to be shut down if a safety threshold is exceeded for 3
seconds. System faults are auto reset faults in that the
system will be allowed to restart automatically after
the 120 second anti-recycle timer times out. The only
exception is after any 3 faults on the same system occur
within 90 minutes, that system will be "locked out" on
the last fault. The lockout condition requires a manual
reset using the system switch. The respective system
switch must be cycled off and on to clear the lockout
fault. See TABLE 17 for the programmable limits for
many of the cutouts.
When multiple systems are operating and a system fault
occurs, the running systems will ramp down and the
faulted system will be shut off and the previously oper-
ating will restart if required after the fault clears and/or
the 120 second anti-recycle timer times out.
In the descriptions of the fault displays that follow, the
fault message will show a YYYYYYYY 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
system safety is in effect, the message will be displayed
to the operator when the Status Key is pressed.
STATUS
KEY
186
SYSTEM SAFETIES (FAULTS)
In some cases, a control panel fault will occur after
a VSD fault, possibly during system shutdown or at
some later time. This is known as an "ALL FAULT"
and these faults will be recorded as such under the HIS-
TORY information stored at the instant of the primary
fault. In some cases, this information may be valuable
in troubleshooting the primary fault. An example of the
"ALL FAULT" history message is shown on Page 204
under the HISTORY Key. When an "ALL FAULT" oc-
curs, associated history information will not be stored. If
an additional fault does not occur, the "ALL FAULTS"
display will indicate NONE. In cases where a VSD fault
occurs during the rampdown of a control panel fault (ie:
low suction pressure, low water temp, etc.), the VSD
fault will be stored as a new fault with the associated
fault information stored at the instant the VSD fault oc-
curred (ie: IGBT Gate Drive, Single Phase Input, VSD
CT Plug, etc.). The control panel fault that occurred
prior to the VSD fault will be stored with the associated
complete data related to the fault as a numerically lower
numbered history in the history buffers.
High Discharge Pressure Cutout
(Software) Fault
The High Discharge Pressure Cutout is a software fault.
A system will fault and shut down with a controlled
ramped shutdown on high discharge pressure when the
discharge pressure rises above 274 PSIG for 0.5 seconds.
The system will be allowed to restart when the discharge
pressure falls to 259 PSIG. The system will also be in-
hibited from starting if the pressure is above 259 PSIG.
The fault message for this safety is shown below:
X indicates the system and YYYYYYYY indicates the
system is in a "FAULT" condition and will restart when
the 120 second anti-recycel timer times out, or "LOCK-
OUT" and will not restart until the operator clears the
fault using the keypad.
LD10605
SYS X YYYYYYYY HIGH DISCHARGE PRESSURE
FORM 201.21-NM2 (616)
JOHNSON CONTROLS
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