On Mon, 14 Apr 2008 09:53:08 -0600, Doug Renwick wrote:
>Has anyone successfully used ca RG-8 or RG-11 center conductor only to
>carry 120 or 240 volts in place of an underground power cable?
There are several issues with this one. First is the obvious one of
moisture. Second -- is the coax rated for carrying mains power? If you
ever had a problem (lightning, a fire), there could be serious legal
and/or insurance issues if it is not.
Third -- NEUTRAL is NOT GROUND. For a 120V circuit, you MUST run a phase
(hot), a neutral, and an equipment (safety) ground. The ground may be
connected to the earth (it MUST be connected to the power system earth).
The neutral MUST NOT be connected to ground or earth anywhere. It can only
be connected to the neutral bus in the panel, and to the neutral terminal
on the outlet (or load) at the other end.
Likewise, for a 240V (only) circuit, you must run two hots ande a ground.
And if you want to run both a 120V load and a 240V load, you must also
pull a neutral.
Fourth, the most "noise-resistant" way you can run a line like this is as
a twisted pair for the phase and neutral, with a third wire as the
equipment ground. If you ran this with coax, it would have to be as two
parallel runs of coax, with one center conductor being the hot (phase),
the other center conductor being the neutral, and the shields being the
equipment ground. The twisted pair is actually FAR better at rejecting
power-frequency magnetic coupling than the coax.
Jim Brown K9YC
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