Many older homes are outfitted with “knob and tube” wiring where individual wires are supported (and kept from touching each other and the building) by ceramic fittings. This method of wiring is not inherently dangerous unless the fittings or wires are damaged - as is often the case during renovation. Knob and tube wiring also has no provision for the “grounding” wire required for three-prong outlets. Today’s technology consists of an insulated cable that contains three or more wires including at least a “hot” wire, a “neutral” wire, and a ground wire. In BX-type cables (armored cable), required in some situations, the wires are contained within a metal sheathing that provides additional protection. This insulated wire is easy to install and provides a high degree of safety. All new wiring must meet the current electrical code.

Installation

A licensed electrician must install all wiring for outlets, fixtures, switches, and appliances. Anyone may install telephone, cable, and structured data lines. You can save some money on electric by running these wires yourself – phone lines may be “chained” together, but each cable and structured data outlet should have a “home run” to the basement where they can be managed individually or hooked into a home automation system.

The rough-in phase for your electrical system includes running all the wiring and installing all the junction boxes necessary to implement your electrical concept plan. The wires will terminate at the breaker box, but will not be made "live" until the electric finish later on in the process.

It is sometimes useful to walk through the building with the electrician who will be performing the installation. This will give you a chance to make any last-minute corrections or additions.

The electric system is the most flexible of the three major systems. While your electrician must follow applicable codes that dictate where wires may run, it is generally possible to get a fixture or outlet pretty much anywhere you want. It is much easier, however, to place fixtures and outlets in frame walls than it is to place them in masonry walls. If you must have an outlet in a masonry wall, the brick has to be chipped out to allow space for the wiring and the outlet or fixture. Then the wall is repaired to hide the wiring. I generally discourage surface-mounted wiring and fixtures, even when allowed by code, unless there is not other alternative.

Safety

Some spaces require specific types of safety features. All outlets near “wet” areas like the kitchen and bathroom must be Ground Fault Circuit Interrupter (GFCI) outlets. A GFCI protected outlet cuts power instantly in the event that a ground fault (for example if you drop your hair dryer into the bathtub) is detected. Also, all outlets in bedrooms must be protected by an “arc-fault” circuit breaker. This special type of breaker helps prevent fires by detecting sparks that can pass between damaged wires within the wall.

Special Cases

If your home is particularly large or unusually shaped, you may want to consider having the electrician install a “sub-panel,” or secondary breaker box. For example, in a three-story house, a sub-panel may be installed in a second floor hallway to serve the second and third floors. Some labor is saved this way because circuits on the upper floors do not have to return all the way to the main box in the basement. It is easier to add additional circuits in the future if need be. Also, if a breaker is tripped, you don’t have to go all the way to the basement to reset it.

Ceiling fans require a different, tougher, ceiling-mounted box than a typical light fixture. Since you can mount a standard light fixture into a ceiling fan box, consider upgrading the mounting in all living spaces even if you don’t intend to have ceiling fans there from the start. That way if you want to add a fan in the future, it will be as easy as replacing the fixture.

The permanent alarm system, if you are purchasing one, should be installed after the general wiring and phone line have been connected.