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How do you comply with NEC 240.87 Non-instantaneous
We never specify devices without an instantaneous
Zone-selective interlocking
Differential Relaying
Maintenance Switch
Something else (please comment)
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 Post subject: Non-instantaneous Trip and NEC 240.87
PostPosted: Sun Jul 03, 2011 3:39 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1637
Location: Scottsdale, Arizona
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.

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PostPosted: Mon Jul 04, 2011 3:12 pm 

Joined: Sat Jul 07, 2007 5:00 pm
Posts: 10
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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