smkettner wrote:
NEC does not allow doubling of the conductors. Just get the right wire size for the job.
And RVIA standards follow NEC.
They are talking about 12V
(TWELVE VOLTS) wiring, this typically falls UNDER 30V AS CLASS TWO wiring.
NEC class 2 wiring does not require splices or connections in junction boxes nor does it require any class two junctions to be visible (in other words junctions can be hid in a wall).
Doubling conductors is addressed in CLASS 1 wiring (which 12V is not).
RVIA "standards" only follows NEC for 120V (ONE HUNDRED TWENTY VOLT) wiring..
For 12V wiring pretty much anything goes including HIDDEN junctions behind paneling..
If you want to get an eye opening experience I would suggest that you remove some of the paneling in your RV.. Once you see how shoddy RVIA wiring is for 12V you will be scared to ever sleep in it again!
Just as an example you can view what I found in my RV..

If you zoom in you will see a bundle of 12V and 120V wiring that is melted together and had even charred some of the paneling..
The wire was so tight that it had chaffed on the metal sleeves in the wall studs (those sleeves are to protect the wire from staples, nails, screws but darn near burnt the trailer down.
You will also notice a bundle of 12V wiring all connected via one huge wire nut hidden behind the paneling.. That was the 12V ground, every 12V circuit came to that junction and was spliced with a single #8 ground wire.. That #8 wire was UNDERSIZED for all the 12V circuits that it served!