How to Hook up a 30-Amp Double Pole Breaker | Hunker A double-pole breaker is needed whenever you're doing 240-volt wiring. It consists of a pair of breakers arranged side by side so they contact alternating bus bars. To install one, attach the hot wires to the breaker, the neutral wire to the neutral bus and ground wire to the ground bus. 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. Circuit Breaker Wiring Diagrams - Do-it-yourself-help This page contains wiring diagrams for a service panel breaker box and circuit breakers including: 15amp, 20amp, 30amp, and 50amp as well as a GFCI breaker and an isolated ground circuit. Circuit Breaker Panel Box Wiring Diagram. This diagram illustrates some of the most common circuits found in a typical 200 amp circuit breaker service panel box.