JOHNSON CONTROLS
235
SECTION 8 - MICROPANEL
FORM 201.23-NM2
ISSUE DATE: 09/25/2020
8
SYSTEM SAFETIES (FAULTS)
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 ex-
ception 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 21 on page 262 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
operating 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 re-
start 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.
LD10605
STATUS
KEY
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
HISTORY information stored at the instant of the pri-
mary fault. In some cases, this information may be
valuable in troubleshooting the primary fault. An ex-
ample of the “ALL FAULT” history message is shown
on Page 263 under the HISTORY key. When an “ALL
FAULT” occurs, 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 (i.e.: low suction pressure, low wa-
ter temp, etc.), the VSD fault will be stored as a new
fault with the associated fault information stored at the
instant the VSD fault occurred (i.e.: 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 con-
trolled 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 sys-
tem will also be inhibited from starting if the pressure
is above 259 psig. The fault message for this safety is
shown below:
SYS X YYYYYYYY HIGH DISCHARGE PRESSURE
X indicates the system and YYYYYYYY indicates
the system is in a “FAULT” condition and will restart
when the 120 second anti-recycle timer times out, or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.
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