On Jun 6, 9:20 am, "Percival P. Cassidy" wrote:
On 06/06/07 08:05 am Doug Miller wrote:

Our house has 3-conductor wiring for the range and dryer. Would it be OK
according to the NEC to run an additional (green) conductor alongside
the existing wiring and replace the receptacles by 4-pin ones? If so,
what gauge? Or would the existing wiring have to be replaced?
Yes it would be OK,
No, it's not. All conductors for a circuit are required to be in the same
raceway or cable. [2005 NEC, Article 300.5(I)]

Except for a few feet of EMT where the wiring for the dryer outlet come
down the wall* (and I could easily get a new ground wire in at the top
end to connect to a 4-pin outlet), there are no raceways: the existing
wiring comes out of the panel (which is surface mounted, so I could
easily run the ground wires out through the same knockout/clamp) and is
stapled to the underside of the joists.

*And it's just occurred to me that running Romex in conduit probably
wasn't kosher either. I wasn't the one who did it.

but it's not necessary.
That's true. Code permits connecting new appliances to *existing* 3-wire
circuits, but prohibits installing *new* 3-wire circuits for this purpose.

If it were me, though, and it wasn't too much effort or expense, I'd pull new
4-wire cable.

That's what I'm trying to decide. Each run is approx. 15ft. What gauge
should be used? -- either for a separate ground wire or for whole new
wiring runs.

I may be wrong, but I thought there were provisions for retrofit to
allow for the addition of the ground to existing wiring, Doug?

Myself, even if it weren't _strictly_ NEC, I'd be comfortable w/
adding the ground to the cable and securing it well to the cable every
so often so it can't be easily separated nor confused w/ some other
cable. Of course, that runs future risk that if try to sell some anal
inspector could force you to fix it at the time. Overall, my choice
would undoubtedly be to simply continue w/ the 3-wire service unless
was rewiring whole house or another major wiring upgrade project
anyway.

As for wire size, 10 ga is certainly the norm for the service. What
to use is whatever is adequate for the breaker for the existing
circuit. I'm not familiar enough w/ the 4-wire code requirements to
know if it allows for the "one size under" or not, but for 15-ft of
#10 I'd use the full size irrespective.

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