On 2005-03-20, Doug Miller wrote:

In article , Wayne Whitney wrote:

It does seem true that sharing a neutral between the two circuits on
separate legs reduces the voltage drop due to the wiring. The current
on the neutral leg is less than on either hot, so the voltage drop due
to the neutral leg is less than it would be with a separate neutral.

Irrelevant. This would do nothing to alter the voltage drop between the supply
and the load, which is the only place it really matters.

I don't believe that is correct. Given a fixed voltage available at
the panel, and for example a resistive load, the hot and neutral wires
are effectively resistors in series with the load. The total
resistance of the circuit will be the resistance of the hot +
resistance of the load + resistance of the neutral. You can't ignore
the neutral just because it is after the load.

Another way of looking at things is that using a shared neutral makes
the overall circuit partially parallel, and two resistors in parallel
have a lower resistance than they do in series.

Further, the resistance of whatever load is applied to the circuit,
even if it's just a single light bulb, is orders of magnitude
greater than the resistance of the conductors.

Well, this is always true, yet on a long run conductors are typically
oversized to avoid an excessive voltage drop. So it does happen.
Admittedly the benefit of reduced voltage drop due to a shared neutral
may be more theoretical than of practical importance, but I do believe
it is real.

Cheers, Wayne