In article ,
Larry Jaques wrote:

On Wed, 08 Dec 2010 14:39:26 -0800, Mike M
wrote:
(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.

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?

I'm not mike, but that's what it says right there. "simultaneously
disconnect" is equivalent to, but more general than,"tied." Obviously
it's been edited over time (normal for code), since otherwise item C and
its exception #2 would not be relevant, having been required in item B...

Personal bias - just use a 240V breaker when you are contemplating
"tieing two together".

And if you want to fret about wire cost (the only real advantage to the
120/240V circuit), skip the neutral altogether and buy ballasts that
will run on 240V (more commonly these days, 85-277 or 120-277, without
taps) and run #14 wire (you've got half the amps to carry - you'll need
a lot of fixtures to warrant #12 and a 20 amp 240V circuit, .vs. #14 and
a 15 amp circuit.) At half an amp or so per 4-lamp F32T8 ballast at
240V, 24 ballasts (circuit derated to 80% for being on a long time) and
96 tubes (384 feet, if you like) on one circuit and 14 ga wire. For that
matter I'm danged if I know why folks are talking 12Ga wire on a
lighting-only circuit that might, at most, be 16 two-tube fixtures, and
probably won't even be that. Unless the ballasts are terrible (awful
power factor, inefficient) that should normally be well within the
capacity of a single 15 amp 120V circuit - and if being split in twain
so that they don't all go out at once (which, if it is really a lighting
only circuit, is far from likely in my experience, but I respect it as a
design goal) it's even more blatantly inside the reach of a 15 amp 120V
circuit to run half or 2/3's of that load on 14Ga wire.

I do overkill, but I try to avoid _stupid_ levels of overkill when it
costs me serious money. 20 amp breakers and/or 12ga wire to feed 2-lamp
4-foot fixtures in this quantity seems rather stupid, even for me - and
I have most of 1000 feet of 12-2NM I happened to buy back when it cost
$118.

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