Nexus7 wrote:
I've come across some wire that is probably 30 years old and is marked
14 gauge. The minimum gauge I want snaking around the house is 12
gauge, so I was about to pull it out when I noticed that the copper is
about as thick as new 12 gauge (and thicker than new 14 gauge). Is the
copper thinner now because of improvements in the manufacturing
process, or something? Is the wire rated by thickness or by current
carrying capacity? If it is current carrying capacity, then are they
using thinner wire because newer copper is a better conductor? This
isn't the plastic insulation I'm talking about, it's about the copper
itself.


I believe that there was some copper clad aluminum wire used for house
wiring a while ago.

Aluminum has only about 70 percent of the conductivity of copper. If
what you found is copper clad aluminum then it makes sense that it's a
bit larger in diameter, but marked 14 gauge because it has the same
current carrying capacity as 14 gauge solid copper wire. Try filing on
the wire and see if you get down to aluminum.

If that's not it, then I'm gonna make a WAG that if your vernier shows
the older copper is in fact solid copper and of a larger diameter, the
difference may be because the newer insulation materials can withstand a
bit more heat than the older stuff could. So, they can dissipate a few
more watts in resistive losses without danger of the insulation going up
in smoke or falling off. But that's a verrrrry WAG I theenk.

Jeff



Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."