Types Of Electrical Wiring In Old Homes

Old electrical wiring types photo guide to types of electrical wiring in older buildings.

Types of electrical wiring in old homes. The oldest type of wiring system found in homes is called knob and tube named for the insulating knobs and tubes are used to run the wiring along and through the house framing knob and tube wiring was run as individual wires one black hot wire and one white neutral wire throughout the home. Electrical service to american homes began in the late 1890s and blossomed from 1920 to 1935 by which time 70 percent of american homes were connected to the electrical utility grid. The common type of home electrical wiring is non metallic or nm cable. In the early days of home wiring from the late 1880s through about.

The coating on nmc cable is non conducting flame resistant and moisture resistant. Knob and tube wiring sometimes abbreviated k t is an early standardized method of electrical wiring in buildings in common use in north america from about 1880 to the 1930s. Electrical wiring insulation in older homes. In the following 200 some years the methods for installing wiring in those homes has seen several important innovations aimed at improving the safety of electrical systems.

You may also know it as romex cable which is the most popular brand name of this type of electrical wiring. Romex is a common type of residential wiring that is categorized by the national electrical code nec as underground feeder uf or non metallic sheathed cable nm and nmc. Electric wiring in older homes ranges from perfectly usable to downright dangerous. Not only could old insulating material rot and expose hot wires but systems that were designed to support a few lights and radios are now being asked to power computers microwaves hair dryers refrigerators and many other modern devices.

Identifying old wiring. Nm and nmc conductors are composed of two or more insulated conductors contained in a non metallic sheath. Modern electrical wiring is encased in plastic which carries three wires inside. The ceramic insulators keep the wires from touching each other and from.

While varying somewhat by area of the country in the u s latin america europe and other areas there are recognizable generations of electrical wiring knob tube greenfield armored cable or bx wiring plastic or nm. Nm cable is usually three or more individual conductors. We describe various old wiring safety hazards code violations and generally bad practices some of which can be lethal such as leaving bare cut off but electrically live wire ends in a building. We illustrate a variety of types of electrical wiring found in older buildings.