Location: ARC Flash Designs


DO NOT DESIGN YOUR RV HOOKUP IN THIS MANNER FOR FEAR OF ARC FLASH, SUBSEQUENT DAMAGE, INJURY, AND POSSIBLE LOSS OF LIFE! We have seen it done, so we are providing a look at how someone arrived at this dangerous conclusion, and why you shouldn't even think about doing so yourself. Long story short, there are AC switches, that are designed to cut the power between two circuits, however, we ask that you don't bet your life on them.

The RV in question was a custom job that came by the office. The inverters from the battery looked good. The power panel after the inverters was standard issue, just like you would find in a mobile home, RV, or marine application, fully outfitted with a main breaker, and individual circuit breakers for kitchen, bathroom, etc. The problem was this little switch that was installed between the inverter and that power panel.

The Bad Reasoning
If you flip the switch, you could just run grid power through the breakers, and avoid the batteries and inverter. The switch installed wasn't a manual transfer switch, or other large circuit isolation switch, just a breaker. The manufacturer swore it would terminally cut the power, the spec sheet agreed.

The Result
The problem arose when the power leaked through the switch, and the sine waves from the power grid and the inverter didn't quite match. BOOM!!! Fire was contained by the circuit breaker box and the breakers above the RV hook up.

The Proper Methods
In electronics, there are usually multiple ways to skin a cat. To supply power to the power grid inside the RV is the challenge. When isolated grids are not an option, the problem has multiple correct answers. Each electrical installation listed below will be safe:
  • Manual Transfer Switch
    Like those found between a generator and the power grid, to fully isolate the power supplies. Cost $300+ in switches, doesn't recharge batteries at same time.
  • Automatic Transfer Switch
    Again, found between a generator and the power grid, to fully isolate the power supplies. Automatic switch is electronically controlled, increasing cost. Cost $1500+ in switchgear, doesn't recharge batteries at the same time.
  • Or simply install a battery charger, let the power switch from AC to DC and back to AC again. Costs $0+ in switch gear, and recharges the batteries at same time.

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