Wire a clock timer using the positive, negative and ground wires taken straight from the circuit breaker. Clock timers are integrated components found between the circuit breaker box and an electrical device.
Most modern timers feature five connection terminals, usually labelled A, 1, 2, 3 and 4. In most applications, the A terminal is not connected to anything. Meanwhile, the numbered terminals attach directly to the power lines. Connect the 1 terminal to the positive power lead wire from the circuit breaker. Then attach the 2 terminal to a positive power output wire, which feeds into the electrical device. Similarly, connect the negative power wire from the circuit breaker to the number 3 terminal on the timer. Wire the adjacent 4 terminal to provide negative power to the electrical device. The timer's operation is simple to understand; when time runs out, an internal switch flips open, severing the connection between each of the pairs of terminals and preventing electricity from reaching the device.
Finally, send a ground wire from the timer to the electrical device. Some timers feature built-in ground wires, while others take ground directly from the circuit breaker. Regardless of its source, the ground wire does not need to be attached to any of the timer terminals and should be sent directly to the electrical device.