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JOHNSON CONTROLS
21
FORM 160.00-O2
ISSUE DATE: 04/30/2019
4
SECTION 4 – SAFETY SHUTDOWNS
GENERAL INFORMATION
Whenever a Safety Shutdown is generated by the Log-
ic/Trigger Board a series of events will occur:
• If the chiller is running at the time of the shut-
down, the Logic/Trigger Board will turn off the
SCR gate outputs.
• If the chiller is running at the time of the shut-
down, the OptiView Control Center will start a
coastdown period (150 seconds for centrifugal
chillers, or a 2 minute lockout for screw chillers).
• The K1 relay will de-energize causing an open
circuit between TB1-1 wire #16 and TB1-2 wire
#53. This action will indicate to the OptiView
Control Center that the LCSSS has shutdown.
The K1 relay will remain de-energized until the
cause of the shutdown has been corrected.
• The Logic/Trigger Board will send a shutdown
code via the serial communications link to the
Micro Board in the OptiView Control Center. The
Micro Board will interpret the shutdown code,
and display a shutdown message on the display of
the OptiView Control Center.
After the coastdown period has timed out, the chiller
may be restarted, if the shutdown is no longer active.
Place the Compressor Switch in the Stop/Reset posi-
tion, and then into the Start position and release. The
chiller will start if no faults are active.
105% MOTOR CURRENT OVERLOAD
The main system microprocessor receives from the
OptiView Control Center a value of current that cor-
responds to 100% FLA. The Digital Signal Processor
gathers the current information from the output CT’s
and converts this information to RMS current. The
RMS current is sent to the main system microproces-
sor where the highest value of the three phase currents
is compared with the 100% FLA times 1.05. When the
highest value of current exceeds this threshold, a 40
second time is started. If this value of current is main-
tained for a period of 40 seconds a Safety shutdown
will occur.
The shutdown message displayed will be
“LCSSS -
105% MOTOR CURRENT OVERLOAD”
.
Possible Problems
• Verify that the programmed FLA is correct on the
OptiView Control Center.
• Verify that the output CT’s are reading current
correctly.
• Ensure that the output current is balanced.
• Verify that the pre-rotation vanes or slide valve
are working properly.
HIGH TEMPERATURE
The starter contains three SCR assemblies. Each as-
sembly has a temperature sensor mounted on the mass
block in front of the SCR. The feedback from the tem-
perature sensors is compared in the main system mi-
croprocessor against a shutdown threshold of 212°F.
If any one of the three sensors exceeds the shutdown
threshold, a Safety shutdown will occur. The coolant
pump will continue to run until all temperatures are
below 109°F.
The shutdown message displayed will be
“LCSSS –
HIGH PHASE X HEATSINK TEMPERATURE -
RUNNING”
, where X is either A, B or C, correspond-
ing to SCR phase assemblies A, B or C respectively.
Possible Problems
• Ensure that the coolant level is proper.
• Verify that the coolant is pink or clear.
• Verify that the coolant pump is working.
• Verify that the heat exchanger is clean, and that
there is condenser water flow.
• Ensure that the heatsink assembly is not clogged.
HIGH INSTANTANEOUS CURRENT
The RMS starting current is programmed on the
OptiView Control Center to a value of 20 – 45% x
Delta LRA (normal value is 45% delta LRA). The
RMS starting current is converted to peak starting
current times 115% to generate a shutdown thresh-
old. If the motor current in any phase ever reaches
this threshold and is maintained for one second, a
Safety shutdown will occur. If the motor current
reaches this threshold for less than one second, a
shutdown will not occur.
The shutdown message displayed will be
“LCSSS -
HIGH INSTANTANEOUS CURRENT”
.
Summary of Contents for SSS 7L-B
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