On 6/22/2010 9:45 AM, dpb wrote:
Pavel314 wrote:
This is a theoretical electrical question, not something I actually
plan to do. Say somebody wants to run a new circuit from the breaker
box to one special outlet, like for a microwave oven or window air
conditioner or something like that. Being an ecconomical sort, this
guy decides that instead of buying the proper gauge wire for the job,
he'll use up some 14 gauge wire which is lying around from a previous
job, but run two hot lines and two ground lines in parallel, as
diagrammed below.

Box: Hot ====================
Load Outlet
Box: Ground==================

So we have two black 14g wires running from the hot connector on the
breaker to the outlet and two white 14g wires running back from the
outlet to the ground in the box. Two questions:

1. What gauge single wire would this be equivalent to in current
carrying capacity? That is, would this be the same as running a single
10g or 8g or what? Maybe 14g / 2 = 7g?

You _could_ look up the wire size tables, but -- two 14's are the area
of between one 12 and one 10. A14 = 0.003, A12 = 0.005, A10 = 0.008

2. This seems to be very unsafe but I'm not sure why. It's probably
against every wiring code everywhere. What's the danger with this set
up?

The prime danger is one of the loss of connection or disparity in the
quality of connection to one of the two conductors as most terminals are
not designed for more than one wire under the connector.

It would be possible to do so by pigtailing ends to a third conductor
for the connection.

AFAIK the arrangement is not condoned by NEC; where specifically it says
it except under the workmanship clause I've no idea since it's patently
silly as two wires of smaller size are more costly than the one larger.

It is quite common to do so with large size wire (1/0 and larger). One
reason is because skin effect diminishes the ampacity increase you get
by increasing size and the other is that it is just plain difficult to
work with large cables.





But, if the ends were stranded, functionally there would really be no
difference between the it and stranded wire of equivalent area.


Again, I'm not going to do this, I'm actually going to go out and buy
the proper gauge wire for my project, but this popped into my head and
I wondered what the rest of you thought about it.


As above, it's not "the right way" for the safety issue in the
connections, mostly which is at least one reason for it not being
Code-acceptable.

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