A 125-volt shore power wiring diagram captures a 30-amp plug. Thirty amps produce approximately 3,750 watts for use by the NEMA TT-30R or National Electrical Manufacturer Association Travel Trailer, which also has a matching receiving plug. The receiving plug has three 125-volt wires originating from the breaker panel.
The breaker panel has three terminals that serve as positive, ground and neutral. These terminals are usually marked as brass or B or a black screw, G or a green screw and W or a silver screw, respectively. Even so, it is important to check the polarity of the wires before making any connections.