On Tue, 24 Apr 2007 14:36:02 -0500, Robert Bonner wrote:
>Romex is trade name of a non-metalic cable. His 12/2 is 2 conductors and a
>bare ground.
As a member of several international EMail reflectors and international
standards committees, I have learned that it is folly to assume that all of the
members know trade names of products that are regional in their use. I spent
the
last 42 years of my professional life in Chicago, where stuff like what you
describe as Romex is illegal, and I dunno nuthin about it. I've never used it
or
anything like it, and had never seen it in houses until I moved to California
last year (where it is called something else).
12-2 describes a pair of #12 conductors. A cable with three #12's is 12-3. Thus
my advice that there must somehow be a third conductor for the safety ground.
And I'm sticking to it. :) If this stuff called Romex has a third conductor
for
ground, that's fine!
In many jurisdictions, including Chicago, steel conduit can be used as the
safety ground, and usually is. Many other jurisdictions say that conduit is not
enough (because if improperly installed the continuity can be degraded over time
( and require that you have a dedicated green wire inside the conduit.
>It is good for 120 V wiring and in the USA if you black or red
>tape the exposed white conductor you can use it as a hot and wire up 220V.
I'm troubled by this last comment. The ground wire MUST be coded green whenever
it is identified. If you're using the cable you've described for 240 volts, the
paired wires must be used for the two 240 pair, and the bare wire must be the
safety ground. If you're using that cable for 120 volts, the pair must be 120V
hot and neutral, and the bare wire still must be the safety ground. But you
CANNOT use only that three conductor cable for BOTH 240V and 120V
simultaneously, because the ground CANNOT be used as a current carrying
conductor.
Another point. Twisted pair cable inherently rejects noise and RFI. Steel
conduit inherently shields the wiring inside it. The unshielded parallel wire
power wiring in my CA house radiates far more noise and receives far more RF
than did the wiring in my Chicago house that is in steel conduit. As a result,
I
have more RFI issues here in CA with antennas 150-200 ft from my house than I
did in Chicago with antennas 15 feet from my house.
73,
Jim Brown K9YC
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