House wiring

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House wiring refers to the various electrical circuits in stalled in a home to enable the use of electrical appliances. The trained professionals who install and service these systems are called electricians.

United States

It starts with a heavy gauge wire "drop" from a nearby public utility pole (or buried wires in some neighborhoods), which first connects to a meter to measure electrical use for billing purposes. This is in turn connected with heavy wire to a main service panel, where there will first be a main circuit breaker. The main breaker acts more as a switch than as a circuit protection device, and allows the de-energization of the wiring in the building so it can be worked on safely.

The main service panel contains 1, 2, or 3 metal buses to distribute the power to smaller circuit breakers, and ground and neutral lug bars. The ground bar is wired to a metal rod driven into the ground nearby. The individual circuit breakers then feed smaller wires that run to various places in the building. The breakers are sized to "protect" the gauge of wire used - for instance, in most modern house wiring, the typical circuit uses a 20 amp breaker and is run with 12 gauge wire. These 20 amp circuits will provide power to all the outlets and switched lighting in the house. The user should be careful not to overload these circuits, since a high current device (such as a hair dryer) could be plugged into each outlet, far exceeding the capacity of the breaker, and tripping it. Usually modern wiring systems distribute the circuits in such a way as to make this less likely.

Some appliances have dedicated circuits, often with higher amperage breakers and heavier wire. Typical examples are electric clothes dryers, stoves, private well pumps, and air conditioning. A few appliances, while not needing higher current circuits, also require dedicated breakers, such as dishwashers.

Older systems are still found in use where fuses take the place of circuit breakers. These usually do not allow sufficient overall current to provide for the array of modern appliances we now take for granted, and so are upgraded as soon as the homeowner can afford it.


European countries use a 230V, 50 Hz standard for domestic power. The power cable entering a domestic property typically passes first through a tamper-evident high-current fuse. This serves both as a last-resort isolator, and a means to disconnect power from the consumer unit for maintenance. An earth or ground line comes in along with the power cables in most modern installations - older houses may take this from a water pipe, but this is being phased out. Following the fuse, both live and neutral cables connect to a tamper-evident power meter for billing purposes. The output of this meter is typically legally defined as the legal demarcation point between utility company and property holder ownership and responsibility.

Typically, the next component will be an isolation switch, allowing the property owner to disconnect power without breaking the tamper-evident seal on the company fuse. Often, this isolator is an RCB which automatically isolates in the event of a fault. It may be a physically separate box, or a component within a consumer unit.

The design of the consumer unit is similar to that of a US distribution system, with common terminal blocks for all neutral and ground wires and a single live rail which connects to all breakers. Depending on age and property size, either fuses or a consumer unit containing breakers may be used. This distributes power to each individual circuit. The number and classes of circuits can vary greatly, and typically include lighting and ring-mains. Newly connected outbuildings should be given their own circuit.

See also

Building trades