Interpreting Selective Coordination for elevators - NEC 620.62

[Magic Gorge]

NEC 620.62 requires selective coordination for elevator circuits when there are more than one fed from the same disconnect. So here is my situation: The elevator panel has a main breaker that is designed to selectively coordinate with the branch breakers. However, each of the elevators also has an enclosed breaker disconnect about 100' downstream of the elevator branch breaker, and these do not selectively coordinate with the upstream main. Is this circuit selectively coordinated? Does selective coordination with the branch breakers insure that the elevator breakers won't trip the upstream main and potentially take the entire panel out of service?

 

[steve66]

I'm interested in what others have to say, but I would say yes, it is selectively coordinated.

The downstream branch breakers are serving as the maintenance disconnects, and wouldn't ever trip on overcurrent due to the upstream branch breaker in the main panel.

 

[ron]

I agree with Steve66.

As long as my tested combination functions properly as a selectively coordinated pair, what is the downside of the downstream breaker / disconnect operating too fast or slow during a downstream fault. It is a "don't care condition".

 

[GoldDigger]

Since the breaker disconnects may show a dynamic impedance while opening there is a slight theoretical chance that they would cause a current versus time profile that was not tested for selective coordination.
I am not sure whether I would worry about it or not.

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[steve66]

Since the breaker disconnects may show a dynamic impedance while opening there is a slight theoretical chance that they would cause a current versus time profile that was not tested for selective coordination.
I am not sure whether I would worry about it or not.

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But the coordinated branch device will have to trip before the main, so I don't see any way for a "slower branch breaker" to have any effect on the main, or the coordinated branch breaker.

 

[gray.one]

Interpreting Selective Coordination for elevators - NEC 620.62

No. If the breakers furthest downstream are not designed & tested to coordinate with the main, then the main may trip first. Unless I'm misunderstanding the something...

I'm picturing two breakers in series with the same rating. The first being in the same panel as the main.

If the feeder breaker and the disconnect are identical, then the answer is still no because the two identical breakers introduce a dynamic impedance and the breakers have not been tested in that setup. Testing is required.


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