Wire Counting in Electrical Boxes Each component in an electrical box represents a different amount of wires. Each insulated wire, all cable clamps combined, all uninsulated wires combined, and each light or other fixture support counts as one wire. Each switch, outlet, or other device is considered to be two wires. The total number of wires in a box is called the "wire count."
The term "wire" includes any conductor within a cable that carries current to or from a load. A conductor is any material through which current flows; it can be aluminum, copper, steel, or any other metal. Wire may also include fiber-optic cables, if they are used as part of an electrical system.
Loads can be anything that uses electricity: lights, heaters, air conditioners, fans, and appliances such as microwaves and dishwashers. Wires carry current to these loads through conductors called "hot wires". Hot wires are always marked with black tape or paint on their outside surfaces to show them as such. Neutral wires are also known as "third wires", "returns", or "phase lines". They are the white wires found in most homes that are connected to loads requiring three-way power (such as heaters) or odd numbers of wires (such as receptacles). These neutral wires do not carry current to loads but return back to the breaker panel when no appliance is plugged into a receptacle.
Jumper wires, on the other hand, count as zero wires because they begin within the box and never leave it.
According to the box, I can receive seven 12 gauge box conductors. I have four conductors with one cable going into the box and one coming out to another receptacle. There are two conductors for each receptacle. Ground wires are counted as one. That's why there are four grounds for four receptacles.
The number of wires in a receptacle is usually specified on the side of the box. If you look closely, you should be able to see it if the box contains four conductors. Receptacle boxes often come in three- or four-wire versions. Sometimes they're not obvious from looking at the box itself but instead shown by a marking on the wall containing the proper wiring diagram. For example, an electric stove might have five conductor outlets while a refrigerator has three. Boxes for devices that use more than one wire for power (such as a three-way light switch) will specify how many conductors are inside. For example, a double-stuff box will take two #4 wires rather than one #4 and one #6 wire.
Conductors are always white or black, except for ground wires which may be red, green, or grey. A word about terminology: even though "conductor" is commonly used to describe any part of an electrical system, it actually means "the conducting element within an electrical circuit".
The diagram below depicts a typical breaker box panel for 120V and 240V circuits. Three wires from the energy meter enter the main panel, namely, hot 1, hot 2, and neutral wires, which are closely attached to the lugs of the main circuit breaker (main switch). The fourth wire from the energy meter is the ground wire, which also enters the main panel but is separated from the other three by a ground strap or metal rod. This ground wire serves as an electrical connection between the house foundation and the utility power line network.
The breaker box is mounted in a secure location away from any electrical equipment that could be damaged by electric shock. It is usually located inside a residential garage or basement, but it can be placed elsewhere if desired. The meter installed at the entrance to the property measures how much electricity you use, which determines your bill. This device may be a single-outlet metal box accessible from the exterior of your home, or it may have separate meters for lights, heaters, air conditioners, and other appliances. This information is used to charge you only for the amount of electricity you actually use. Any surplus capacity in the system provides backup power in case of a blackout or other emergency.
Electricity flows along paths called circuits. Inside your house, these circuits include the power supply cable that leads from the breaker box to each appliance that uses electricity.