Wiring methods have changed over the years. Improvements in electrical wiring over the years were not just in materials used but also in installation methods. All of these improvements help to provide safe and reliable wiring in the home. The ages below are based on the historic homes and building trends in the New Orleans area.
1880 – 1940 – Knob & Tube wiring was the first type of electrical wiring in homes. This type of wiring consisted of two single wires run parallel within wall or ceiling cavities. The wires were run through joists and stud holes through porcelain tubes and supported along their length with porcelain knob insulators which were nailed down. Knob & Tube wiring was labor intensive and expensive to install and eventually replaced with Rag wire.
1940 – 1950 – Rag Wire or (old cloth sheathing) Issues with rag wire include the insulation deteriorating and becomes brittle with age, also the lack of a grounding conductor.
1960-65 – NM (non-metallic) A cable that incorporated the use of a bare ground wire run with a hot and neutral wire concealed in an outer sheath made of plastic vinyl. This update made installation easy to install and is still used today.
1965 – 1973 Aluminum wiring – Due to the sudden escalating price of copper, single-strand (solid conductor) aluminum wiring was sometimes substituted for copper branch circuit wiring. Over time aluminum branch circuit wiring will become defective faster than copper due to certain qualities of the metal.
Today – Newer Romex – NM (non-metallic) is flexible, heat and fire resistant, easy to install, and relatively inexpensive. Each conductor is insulated and the entire bundle is insulated in a color coded PVC jacket. Color coding is based on wire size.
For example: 15 amp circuit uses a 14 gauge wire, typically white PVC jacket
20 amp circuit uses a 12 gauge wire, typically yellow PVC jacket
