# circuit breaker

Discussion in 'General Electronics Chat' started by sergiyny, Jan 20, 2014.

1. ### sergiyny Thread Starter New Member

Jan 19, 2014
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I have a question. If nominal current is 112A, then would i need 125A CB or 100A CB? and in this case i would need #2(115A) conductor. Will this CB ever trip if nominal current is less than the rating of CB? Does this mean that this wire will start burning if current in the wire will be 120A which bigger than nominal current and current at which wire is rated, but less than CB rating. And how do i find Ampere Frame in this case? Could someone please explain this to me?

Last edited: Jan 20, 2014
2. ### inwo Well-Known Member

Nov 7, 2013
2,435
315
It depends on what kind of load. On all the time?

Also conductor size and length. #2 cu. ?

A 100 amp breaker may hold 112 amps for short periods.

A 125 seems right if conductors are sized properly.

3. ### sergiyny Thread Starter New Member

Jan 19, 2014
2
0
Let's say continuous lighting load. Length is <100ft.

4. ### inwo Well-Known Member

Nov 7, 2013
2,435
315
In MN. and WI. we use nec.

Lighting load can be on over 3 hours, so it is considered continuous load.

That requires conductors and overcurrent protection calculated at 125%

#1 cu. and 150 amp breaker.

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