selective coordination for devices in series.

[binwork91]

Question: In emergency system, if main breaker panelboard's main breaker is larger than the upstream breaker. Do they required selectively coordination?

NEC code 700.27
Exception: Selective coordination shall not be required in (1) or (2):
(2) Between overcurrent protective devices of the same size (ampere rating) in series.

So what if down stream overcurrent protective device is large than the upstream breaker, does it still required selectively coordination?

 

[don_resqcapt19]

I don't see than language in the code book. The only exception I see says:

Exception:
Selective coordination shall not be required between two overcurrent devices located in series if no loads are connected in parallel with the downstream device.

Also what code edition are you working with? The 2011 is the last time this rule was in 700.27. It moved to 700.28 in the 2014 and then to 700.32 for the 2017 and 2020. All four of those editions have the same exception.

 

[binwork91]

I don't see than language in the code book. The only exception I see says:

Also what code edition are you working with? The 2011 is the last time this rule was in 700.27. It moved to 700.28 in the 2014 and then to 700.32 for the 2017 and 2020. All four of those editions have the same exception.

Sorry, my bad. I opened the 2008 code. Thank you for the information. The new code solved my question.