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Can a circuit breaker be used instead of an Isolator?

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tomzie27

Electrical
Jan 29, 2007
2
Is it Ok to use a 1250A circuit breaker incorporated in the PSU in lieu of an external Isolator(Heavy duty, 1250A) in isolating a power supply unit from a substation.

Also what is the airgap between the contacts of an Isolator and that of a circuit breaker too?
 
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There's not enough information in your post to give an answer. If you are talking high voltage then an open circuit breaker alone may not be acceptable as a point of isolation for work on equipment downstream, depending on the HV Safety Rules in effect at your location.
Regards
Marmite
 
There are circuit breaker "trucks" that can be removed from the corresponding cabinet, which is then locked. They can be used as isolators. But a single CB may not be used - there is a need to see the "missing link" visually in most codes.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
i understand your question in 2 ways:

1. if you mean that is it enough to use the incorporated CB, or do you still have to buy an external unit, i think the answer is no you do not need to buy any more units and you can limit yourself to the CB on the PSU.

2. if you mean that a heavy duty isolator can replace a C.B. because it can open on full load and close on short circuit, then i think you cannot because after you close on a short circuit the isolator is toast unless there is a circuit breaker on the same line to interrupt this fault.
 
Many entities require a "visible air gap" for isolation for safety purposes. This translates to a knife switch or similar disconnect for isolation, or a truck-mounted circuit breaker that can be racked out of its cubicle and locked.



old field guy
 
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