Older Electrical Wiring

Older electrical wiring is still found in homes that have been standing for a long time. As it is still functional, the electrical wiring may be working fine. An understanding of this wiring helps in identifying potential hazards and resolving them. There are different types of older wiring found in antique homes. Each presents different problems requiring varying solutions.
Aluminium electrical wiring

Aluminium wiring came into use in the 1960s. This was when copper which was the predominant wiring became too expensive. Copper was a wonderful conductor of electricity. Aluminium was not as good a conductor. This became plain soon after its use begun when problems emerged. Some of these problems included burned insulation on the wiring and flickering lights.

This form of older electrical wiring had significant differences with copper. For example, it expanded more when heated unlike its predecessor. It also formed rust which further reduced its conductivity. Aluminum was also softer than copper. It experienced breakage many times.

Aluminium wiring was considered to be a fire hazard in the home, and still can be. This prompted the design of special connectors to reduce the danger aluminium posed. These included small receptacles, large receptacles, twist-on wire nuts and switches. The labels on these connectors were CO-ALR, AL-CU and CU-AL.

Copper clad aluminium wire

The installation of this wiring in many homes started between 1972 and 1975. Later use was upon the preference of the electricians installing it. Copper cladding covers the aluminium core in this wiring. This helps to improve its performance. Where it is safely installed this wiring is completely safe. There have been no reports of it having the hazardous effects of plain aluminium wiring. These wires look like copper cables in older homes. The only way to tell that this is the wiring in place other than reading a label is to cut into the wire. Making a horizontal cut along the wire will reveal the white aluminium core. The cut will not compromise its performance.
Knob and tube electrical wiring
This is one of the oldest forms of electrical wiring using only a hot and a neutral wire. These wires came insulated with rubberized cloth. Often they will have cracked due to overheating. This kind of wiring also does not have an electrical ground path. Insulation of these wires was through ceramic tubes whenever it passed through wood. While this form of older electrical wiring is not illegal it has some drawbacks. As it is not grounded one cannot safely use appliances that have grounded plugs with it. Also, many times the wiring has experienced some damage over the years. This comes from rodents chewing on it or people stepping on it. When you expect installation of more insulation, it is good to change it. When covers have experienced fracturing or soaking, change the wiring. Irregular circuits may also need a change.

Extension cord electrical wiring

Many older buildings use extension cords to add receptacles and lighting circuits. You will see these mounted on ceilings and walls and sometimes through the walls. Evidently the house does not have enough circuits for its uses. The presence of these extension cords should provoke further investigation. Oftentimes this suggests that there could be other faulty wiring in the building. There is a solution to this older electrical wiring. One of this is to use heavy duty extension cords of 14-gauge or thicker and to add more outlets.


Some older forms of insulation used in electrical wiring may be obsolete today. Materials used earlier for electric wire insulation included:
  • asbestos
  • fabric covered non metallic cables
  • rubber
  • plastic insulated wiring
Asbestos insulated electrical wiring
Asbestos was a material used for insulating electrical wiring. It offered various advantages that it offered. It was durable material offering fire and heat resistance and acid resistance. Sometimes its difficult to differentiate asbestos insulated or fabric covered electrical wiring. Asbestos based insulation many times appears in white or gray fabric. Appearance can be deceiving though. The exposure hazard from asbestos insulated wiring is low. The material does not fray easily and it is also enclosed in walls and house cavities. Electrical codes act as a guide when deciding whether to replace this wire insulation or not.

Fabric covered non metallic cable electric insulation

The non-metallic cable (NMC) came covered by a cotton braid. The cotton braid was varnish sealed in earlier versions of this insulation. Later designs made use of rayon. The fabric used was often silver colored. White, black and sometimes brown colors appear as well. The wire inside that cable was often insulated by rubber and later plastic. Many times when you come across this form of insulation it is fraying and has deteriorated in some way. This could be a sign of overheating. You will need to replace this with what the local electrical codes dictate in the area. Some need electrical conduits or metallic armored cables.

Rubber insulated electrical wiring

Rubber was the first material used for insulation produced both economically and mechanically. It was not the first material used as insulation. Previously used materials included wood, rope and tarred fabric. Rubber came into use in the 1890s because it was water proof and fire proof. Today many electrical codes call for replacement of rubber insulation. You can do this with metallic armored cables and or electrical conduits. At first glance rubber insulated wiring may look intact. But further investigation into the wiring could reveal deterioration of the wire.
Plastic insulated electric wiring
These non-metallic cables came into use in the 1920s. They began replacing rubber and plastic in the 1960s. One of the major brands of these cables is Romex. The industry adopted this name for all non-metallic cables. They replaced fabric-based wire insulation. They may not need to replacing unless damaged or required by the local electrical codes. Different localities may have different electrical codes. Know their specific requirements on electrical wiring and electrical cable insulation. Though the older electrical wiring may still be safe, compliance may necessitate change. Non-metallic cable is designed for interior use in dry locations. Just about all of the wiring in a modern home is non-metallic cable.