How to Install a 240-Volt Circuit Breaker - The Spruce A 3-wire, 240-volt circuit has two hot wires—each supplying 120 volts for a total of 240—and an equipment ground wire. A 120-volt circuit has only one hot wire connected to the breaker plus a neutral wire connected to the neutral bus bar in the service panel.Author: Bob Formisano How to Wire a 240 Volt Circuit | Gone Outdoors | Your Take your volt-ohm meter and turn it to the voltage position to check that the main power is off. You can place the leads one each to each of the main bus bars that are running down the center of the box. The meter should read 0. To wire a 240-volt circuit, you must have a double-pole circuit breaker.