Look here:
See 240.20 Ungrounded Conductors.(B)(1)
Multiwire Branch Circuit.
Except where limited by 210.4(B), individual single-pole circuit breakers, with or without approved handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.
The NEC doesn't tell you about the open neutral hazards when working on a circuit of this type, and too many have found out otherwise!
I always say that if you hear a "loud yell and then a thump" you'll probably find out that the reason was when someone was changing a ballast .... only those who are qualified persons will understand this hazard!
The rule cited above, has been in the code for many years and was designed to overcome the questions associated with common trip or handle tied circuit breakers in an offfice occupancy.
Note:
The new 2005 NEC may require "listed" instead of "approved" handle ties because in their wisdom some would allow a nail or piece of wire, and say that it is "approved"
See that definition in Article 100.
See also Article 605
605.8 Freestanding-Type Partitions, Cord-and-Plug-Connected.
(D) Multiwire Circuits, Not Permitted.
Individual partitions or groups of interconnected individual partitions shall not contain multiwire circuits.
FPN: See 210.4 for circuits supplying partitions in 605.6 and 605.7.
[This message has been edited by Joe Tedesco (edited 06-14-2003).]
