In article . net, "Frank Ketchum" wrote:

"John Moorhead" wrote in message
news
Folks -

I'm back... Now it's a wiring question. I'd like to run a string of
outlets at benchtop height, and run two circuits. I'll put a pair of
outlets in each box, 1 on each circuit. Can I safely run 12/3 for a pair
of 20 amp circuits using a common neutral (white) and ground? I'd run the
red wire (marked black) to one outlet and the black to the other. The two
outlets would share the white wire, along with the grounds.


I do not believe this is allowed by the NEC. If you think about it, each of
the two hots will be on 20 amp breakers and will be current limited to 20
amps. The neutral will have to carry the sum of the two circuits, or
potentially 40 amps back to the panel. 12 AWG wire is not rated for 40
amps! You may be allowed to do this if you derate the circuit, but I doubt
you will want to do this.

Geez. Here we go again.

Yes, it is allowed by the NEC, as long as the two hot conductors are on
opposite legs of the 240V service, and a single disconnect, disconnects them
both. This is easily implemented by using a single double-pole breaker. With
the two hots on opposite legs, the current in the neutral is the *difference*
of the currents in the individual hot conductors, *not* the sum, and thus can
never exceed 20 amps. There just isn't a problem with doing this.

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

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