[VAC] Wiring: solid -vs- stranded

["Bob Harper" <rharper@xxxxxxxxxx>]

Hi-

I'm back after a long absence ... again.  Still piddling away on the '62
Globe Trotter in South Carolina.

Current project is wiring.  I will have some 110 V, some 12V.  I'm using the
Iota converter w/ IQ3 "charge wizard" and a Magnetek 80D distribution box w/
breakers for 110 and fuses for 12V.  I had just about been convinced to
spend big bucks using tinned boat cable (stranded, different inner colors
than normal Romex, copper wire is tin coated to prevent corrosion) when it
occurred to me:  if stranded wire is so important, why is the original
wiring for the 110V solid?  In 40 years, it's never failed to the best of my
knowledge, and this trailer's been overseas.  Ditto on the tinning: I don't
have any plans to take the Trotter out on the water, and the original wire
isn't tinned, so why bother?  I understand that the great majority of wiring
system failures is at the connections, not in the wire itself.  Tinning the
bared wire ends wouldn't be a big deal if it's really important.

So I'm thinking, why don't I just use a different color of Romex for my 12V
and save a wad of cash?  250' is only $20-$25.  All of the Romex I've found
is solid, but I've seen outer casings in yellow, black, gray and white.  I
believe inner wire insulation on all 3 choices will be black, white, and
bare copper.  Boxes could be clearly labeled for 12V or 110V on the inside
in addition to the different casing color.

If this is a legitimate possibility, what about the potential of using the
2-conductor w/ground Romex as a way of running 2 different 12V circuits on
one line?  EG: Black is hot to one circuit, white is hot to another circuit,
and the bare copper is ground to both.  Is this allowed in 12V wiring?  Even
if not, just using the black as 12V (+) and the bare copper as 12V (-) would
be a tremendous savings.  And readily available.  The white could be nipped
out of sight.  Various gauges are available (as dictated by the load and the
length and length of the circuit).

Feedback appreciated.  In case it's not readily apparent, I'm a
shoot-from-the-hip electrician (this week) without a bit of training but a
fair amount of experience.  Just not in 12V.

Bob Harper
BH62GT/SC