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Electrical Circuits

Electrical Panel and Circuit Wiring Diagram

Electrical Panel

120 V


240 V

A & B


Two pole

circuit breaker

for electric oven, dryer and/or air conditioner

Ground bar

Question or Comment?

Household Circuits Diagram

These diagrams show a typical circuit path from the power company through the main electrical panel and to the outlets (light sockets, switches, and receptacles).

120V A&B Phase

From power company


Electric meter

Ground and neutral are connected together

in one location only, at the neutral point either at the power company transformer or in the main electrical panel.

The potential difference between the A phase and B phase is 240 volts.

Main breaker



Electrical Panel Diagram

NM cable

Electrical Panel

A phase

power bus

To ground

B phase

power bus


Circuit Capacity

Circuit capacity depends on the voltage and current ratings of wires and circuit breakers. When a circuit is rated for 15 amps, the wires and circuit breakers must be rated for at least 15 amps. The circuit is rated for the lowest current rating of wire or circuit breaker. For example, if the wire is rated for 15 amps, the circuit should not have a 20 amp breaker even if the breaker trips frequently.

It is very important that a 20 amp (or higher) circuit breaker NOT be used on a circuit with a wire rated for 15 amps or less.