Electrical Help Needed

enblethen wrote:
Wire size and type of wire is determination of circuit breaker or fuse size.
Must remember that the wire in question is fed from two directions. Battery feeds wire toward the 12-volt DC power distribution panel. The converter feeds wire to the 12-volt distribution panel then to the battery.
SAE type wire can carry more amperage than AWG building wire.

Ampacity depends on type of insulation and if it is enclosed or open air, lots of factors goes into what is deemed as safe or not.

Ampacity is highest without any insulation, but then you would now be back to knob and tube..

If you look at a ampacity chart it does vary with the type of insulation and type of wire (copper or Aluminum)..

Found HERE


Click For Full-Size Image.

Romex has 60C temp rating and hence is limited to 40A.

"Building wire however has insulation ratings of 75C and 90C and ampacity of 50A and 55A respectively..

However, RV manufacturers do not use either Romex or Building wire, they use the most dirt cheapest plastic covered insulated wire as possible.. It is a much lower grade of insulation (and unmarked) which has a far lower melting point than Romex.

I would not trust RV 8 ga wire above Romex wire ampacity.

There is "Primary" wire typically used for automotive uses which you basically mentioned as "SAE", yes it has a higher temp insulation rated as 105C (the real SAE wire), but, from my experiences, RV manufacturers are using really cheap wire that doesn't come close to 105C melting point and isn't SAE wire.. I pulled lots of the RV wiring out of my current TT when rebuilding it and scrapped that wire. If you wanted to solder a connection the insulation easily melted back, much easier than building wire or even Romex.