Battery disconnect wires

Toyanvil, I only pointed out sections of the Code that explicitly deal with what are obviously dc circuits to show that they are covered. I was not suggesting they were the only sections covering dc circuits. The way the NEC works is that it’s prescritive, meaning that unless there is an exception noted you have to do what it says. There are no such general exceptions for say 12V dc circuits so you have to follow all the applicable Code articles for those systems just like you would for 120Vac. So that means if you are wiring up an off grid home at 12 or 24Vdc you need to maintain a contiguous grounded neutral and place all your disconnects and over current protection in the hot line, just like in a grid powered building.

That is for an off grid residence. If that residence is subject to electrical inspection then it would be reviewed for code compliance just as if it was ac powered. I have seen many such systems installed by my solar customers rejected for not following the NEC. As for what an electrical inspector would say about an RV, most likely he’d just say he doesn’t have jurisdiction over it and wouldn’t look at it. That leads us back to NFPA 1192 and the RVIA low voltage standard which I am too stingy to drop $45 on. That and the NEC are going to be the most appropriate US standards for electrical systems in RV’s. If anyone wants to “crowd fund” me to get the standard and review it I’ll be happy to 😄.

Your current 4 way switch in the positive battery leg is a good example of why the battery disconnect should be in the positive line. By keeping everything that can open the circuit in the ungrounded (positive) line you always keep a solid ground reference (negative) and can manage multiple sources without inadvertently connecting things together that shouldn’t be or disconnecting things that should stay connected. When you get into more complex circuits with multiple sources like solar, generators, grid supplied chargers, inverters, multiple battery banks, etc etc you can easily find where they hid the smoke unless you keep a common ground reference.