Many of you might have worked on vessel equipped with Hyundai HAT series Air Circuit Breakers which proves to be very reliable and efficient but…like any other machineries it requires periodical checks and maintenance. If this is not properly done the result it might be a failing UVT coil or breaker fail to close when required.
In the video below you can find how the breaker is troubleshooted and tested on the specialized workshop test bench.
In this post will discuss about ACB troubleshooting onboard in case that will fail to close.
Here below there are some instructions on how to troubleshoot a Hyundai HiAN Series Air Circuit Breaker (ACB).

Example of HiAN air circuit breaker
The possible causes of breaker failure can be:
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- HANDLE SHUTTER is open
- UVT coil has malfunction electrically or mechanically.
If the UVT COIL is drop down, check the output voltage of UVT controller (C1,
C2).
1) about DC19V : change UVT coil with new one.
2) about “zero” : change UVT controller with new one.

Example of UVT controller
Lock UVT Coil to energized position by rotating Lock Lever clockwise after lift up the actuator pin in order to close ACB temporary.
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- Malfunction of mechanism
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When ACB has been operated for long time, it should be checked as following
procedure.
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- ACB Circuit breaker Load off
- Rack out ACB to isolation position.
- Release Front Cover.
- Take off OCR (release 3 bolts).
5. Check whether Closing Latch could be moved well when Close Button is pushed.
If not, check whether harden grease make this un-smoothness or not.
The Closing rod should be moved to arrow direction after motor charging.
If it is not, it is impossible to close ACB.
6. Check whether the relevant connected levers could be moved well when Open
Button is pushed
7. If the Closing Latch and relevant closing parts are not moved after 5~6 trials, clean the harden grease and spray the lubricant, such as WD-40, in order to clean the harden grease and make smoothness.
If main spring is charged successfully, the half circuit shape parts, Latch unit cam, will move arrow direction. But when grease is to be hard, these did not move fully.
8. Unlock UVT coil and assemble OCR and Front Cover reversely.
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- ACB does not work mechanically when push the trip button of ACB body.
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If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World and will try to answer to all your queries. You can use the feedback button as well!
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Source and Bibliography:
- YouTube video training credit – C&A STAVROS KASSIDIARIS S.A
- Hyundai Heavy Industries – Electro Electric Systems Customer Service Department