How to Install a 30 Amp Breaker & Plug | Hunker Cut a hole in the wall where you will locate your 30-amp plug by first tracing around the template Turn the power off to your breaker panel. Locate the main breaker panel at the top of your breaker Remove the cover to your breaker panel, exposing all wiring and breakers. Use a two-prong Pull a length of 10/3 NM cable from your 30-amp plug location back to your main breaker panel. See all full list on hunker How to Wire up a Travel Trailer 30 Amp Box | Hunker The National Electric Code (NEC) states that any outside receptacle must be "ground fault circuit interrupter (GFCI)." Subsequently, you must install a GFCI receptacle or a GFCI breaker. The 30-amp receptacle will need to be wired to a 30-amp single-pole GFCI breaker in the panel box. This will provide 125 volts to the travel trailer receptacle.