INCIDENT REPORT for
AIR-COOLED CHILLER No.1 SHUTDOWN on 22-25 SEP
Location:
Report Date:
Prepared by:
Brief Descriptions:
It was informed by JEC A/C Team that the HV Switch of air-cooled chiller no.1 was
producing abnormal noise during running on 22 Sep 2014. Our ELE Staffs have
arrived in there and shut down the system for a complete inspection. After that Our
HV contractor with us were found out that the VCB, in ‘Star’ connection, was
malfunction due to the VCB cannot fully closed on 24 Sep 2014.
The air-cooled chiller no.1 has resumed normal at around 14:05 after replacing the
existing spare VCB which was supplied by client.
Investigation and Findings:
Further to the complete inspection with contractor, we would report as below:
Item no.
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Photo
Faults Findings
( In ‘Star’ Connection)
The switching mechanism
of VCB induced a serious
of problems:
1) The motor of spring
charger was charging
constantly.
2) The VCB wasn’t closed
completely in normal
status.
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2
(VCB, inclusive of
Incomer, Start and Star
connection)
1) The high resistance
( >100Ω) contacts were
found at the built-in
auxiliary switch.
2) Oxidized and rusty
contacts were found out.
Discussion and Conclusion:
For the problem of item no.1, a spare VCB which supplied by client was tested and It
was then used for replacing the defective VCB. Before restarting the chiller, we have
carried out dry run test to make sure the control wiring circuit was in working
condition.
For the problem of item no.2, the chiller operation maybe affected if there was any
further degrading of the auxiliary contacts in VCB. The chiller no.1 can be operated
but better to put it in standby condition before repairing work.
Recommended Improvement:
As talked with our contractor, both of us recommended that keeping a new spare
VCB of great advantage to the system. And we also suggested to replacing the built-in
degraded auxiliary contacts which were in need.
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Reference Drawing:
Electrical schematic diagram of MCC-3-1
Fault VCB
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