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Non-instantaneous Trip and NEC 240.87
https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=1771		 Page 1 of 1
Author:  Jim Phillips (brainfiller) [ Sun Jul 03, 2011 3:39 pm ]
Post subject:  Non-instantaneous Trip and NEC 240.87
240.87 Noninstantaneous
Where a circuit breaker is utilized without an instantaneous trip, one of the following or approved equivalent means shall be provided:
[INDENT](1) Zone-selective interlocking
(2) Differential Relaying
(3) Energy-reducing maintenance switching with local status indicator.
[/INDENT]Do you use protective devices without an instantaneous as part of the design and if so, what changes (if any) have you made to comply with this article?
[INDENT]
  • We never specify devices without an instantaneous trip.
  • Zone selective interlocking
  • Differential Relaying
  • Maintenance Switch
  • Something else (please comment)
[/INDENT]Select all that apply.
Author:  J Scott [ Mon Jul 04, 2011 3:12 pm ]
Post subject: 
We have not had a design with L,S only (no Instantaneous) since the 2011 NEC came out. The next time we do, we will likely specify a maintenance switch. Seems like the simpler approach.
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