Code Q&A
Jun 13, 2007 7:47 PM, By Mike Holt
Q. When a lighting and appliance panelboard is fed from the secondary of a 3-phase transformer, is the panelboard required to have a main breaker installed in it?
A. No. Lighting and appliance branch-circuit panelboards supplied from a transformer, as permitted in 240.21(C), must have overcurrent protection for the panelboard on the secondary side of the transformer. The required overcurrent protection can be in a separate enclosure ahead of the panelboard, or it can be in the panelboard [408.36(A), 408.36(A) Ex. 1, and 408.36(D)].
Exception: A panelboard supplied by a 2-wire system or a 3-wire, delta/delta-connected, 3-phase system, is considered protected by the primary protection device when installed in accordance with 240.4(F) and 240.21(C)(1).
Note: A lighting and appliance branch-circuit panelboard is one with more than 10% of its overcurrent protection devices protecting “lighting and appliance branch circuits,” which are 30A or less circuits with neutral connections [408.34(A)].
Acceptable Use Policy blog comments powered by Disqus
Want to use this article? Click here for options!
© 2009 Penton Media, Inc.
