JOHNSON CONTROLS
244
FORM 201.23-NM2
ISSUE DATE: 3/9/2015
SECTION 8 - MICROPANEL
UNIT YYYYYYYY
LOW LEAVING CHILLED LIQUID TEMP
The unit is inhibited from starting any time the chilled
liquid temperature is below the cutout plus 4°F.
VSD Communications Failure Fault
The VSD Communications Failure is to prevent the
unit from trying to run, if the Chiller Control Board
never initializes communications with the VSD Logic
Board. The unit will also shut down with a controlled
ramped shutdown if the Chiller Control Board loses
communications with the VSD Logic Board while the
chiller is operating.
On power-up, the Chiller Microprocessor Board will
attempt to initialize communications with the VSD
Logic Board. The control panel will request data from
the VSD, which includes the number of compressors
and the VSD software version. Once these data points
have been received by the Chiller Control Board, and
have been successfully initialized, the Chiller Control
Board will not request them again. If the comms con-
nection fails to occur, the Chiller Control Board will
prevent the chiller from operating and a fault message
will be displayed.
During normal operation, if the control panel Chiller
Control Board receives no valid response to messages
for 8 seconds, the unit will shut down all compressors
on a Comms fault. The Chiller Control Board will con-
tinue to send messages to the VSD while faulted. The
unit will be inhibited from starting until communica-
tions is established. The fault will automatically reset
when the Chiller Control Board receives a valid re-
sponse from the VSD for a data request. Shown below
is an example of a Comms Failure fault message:
UNIT YYYYYYYY
VSD COMMUNICATIONS FAILURE
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 17 on page 271 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
Summary of Contents for YCIV0157
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