Larry Jaques wrote:
On Wed, 08 Dec 2010 14:39:26 -0800, Mike M
wrote:

snip


210.4 Multiwire Branch Circuits.
(A) General. Branch circuits recognized by this article
shall be permitted as multiwire circuits. A multiwire circuit
shall be permitted to be considered as multiple circuits. All
conductors of a multiwire branch circuit shall originate

from the same panelboard or similar distribution equipment.

FPN: A 3-phase, 4-wire, wye-connected power system
used to supply power to nonlinear loads may necessitate
that the power system design allow for the possibility of
high harmonic currents on the neutral conductor.
(B) Disconnecting Means. Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.
(C) Line-to-Neutral Loads. Multiwire branch circuits
shall supply only line-to-neutral loads.
Exception No. 1: A multiwire branch circuit that supplies
only one utilization equipment.
Exception No. 2: Where all ungrounded conductors of the
multiwire branch circuit are opened simultaneously by the
branch-circuit overcurrent device.
FPN: See 300.13(B) for continuity of grounded conductor
on multiwire circuits.
(D) Grouping. The ungrounded and grounded conductors
of each multiwire branch circuit shall be grouped by wire
ties or similar means in at least one location within the
panelboard or other point of origination.
Exception: The requirement for grouping shall not apply if
the circuit enters from a cable or raceway unique to the
circuit that makes the grouping obvious.
ARTICLE 210—BRANCH CIRCUITS 210.4
2008 Edition NATIONAL ELECTRICAL CODE


Mike, can you point out the particular text in that extract which
states the demand to tie two 120v breakers together when supplying
120v equipment?



For deciphering the 2008 code see:

http://www.inspectapedia.com/electric/multiwir.htm

--
Jack Novak
Buffalo, NY - USA