How Electrical Wiring Was Done Before Romex

Before the development of Romex wiring, homes and buildings relied on a variety of earlier electrical wiring methods. Understanding how electrical wiring was done in the past provides insight into how far wiring technology has advanced over the years.

Knob and Tube Wiring

Knob and tube wiring was commonly used from about 1880 to the 1930s. It gets its name from the ceramic knobs that insulate the wires and the tubes that protect wires through open spaces.

Key features:

• Wires were individual copper conductors with cotton or rubber insulation. This insulation could degrade over time, leading to exposed live wires.

• Wires were held apart by ceramic knobs and run through protective tubes where they passed through walls and open spaces. This provided protection and prevented contact between wires.

• It was an open wiring method - wires were not enclosed in conduits or boxes. This increased fire risk compared to modern wiring.

• Wires were run in straight lines rather than in bundles like modern NM cables. This made running wires easier but used more space.

• No grounding wire was used. Appliances and fixtures were not grounded for safety.

Knob and tube wiring powered many homes in the early 20th century. However, it lacks safety features expected in modern wiring, so most homes with knob and tube have upgraded.

Armored Cable (AC)

Armored cable, sometimes called BX wiring, gained popularity in the 1920s and 30s. It improves safety compared to open knob and tube wiring.

Key features:

• Wires are bundled together into a flexible metal-wrapped cable. The steel armor protects the wires from damage.

• The metal wrapping is grounded, improving safety. This was an early grounded wiring method.

• More flexible and compact than knob and tube, easier to install in cramped spaces.

• Uses rubber-insulated copper wires, typically two insulated wires and an uninsulated grounding wire.

While BX armor cable fixed some knob and tube safety issues, it is thick and stiff compared to modern NM wires. Homes upgraded from armored cable as flexible NM cables became widespread in the 1950s and 60s.

Conduit Wiring

Conduit wiring systems encase wires in rigid or flexible metal tubes. Wires are pulled through the conduit which protects them physically and from contact with other wires.

Key attributes:

• Wires are run through metal conduit - rigid, thin-walled, or flexible tubing. More protection than open wiring.

• Conduit is more moisture-resistant than other early wiring, good for damp areas.

• Electrical boxes connect conduit sections. Running new wires is simplified by pulling them through existing conduit.

• Requires more labor for installation than open wiring methods.

• Early versions lacked modern grounding or wiring insulation. Safety has improved over time.

Conduit is still used for commercial and industrial buildings today when extra physical protection is needed. Early versions without modern insulation lacked safety features.

Cloth-Insulated Wires

One of the oldest wiring methods used simple cloth-wrapped wires installed along walls, ceilings, and wood trim.

Features:

• Individual copper wires with cloth fiber insulation. Provides no moisture resistance.

• Exposed wiring is an electrocution and fire risk. Insulation breaks down over time.

• Can be installed by tacking wires against walls or running inside wood trim. Limited to dry areas.

• No included safety features - no grounding, junction boxes, or circuit breakers.

This wiring powered some of the earliest electrified buildings in the late 19th century. It lacks any modern protections. Use of cloth wiring decreased as rubber and plastic insulation was adopted.

Other Early Wiring Methods

Many other innovative wiring systems came and went in the early days of electrical use:

• Gas pipe used to distribute power in some early structures. Hazardous and prone to issues from corrosion.

• Metal molding along ceilings, floors, and corners to hide wires. Precursor to wire molding still used today.

• Wood molding with wires channeled inside. Cheap but high fire risk from heat concentration.

• Directly mounting wires to walls and ceilings with staples/nails. Very unsafe but easy.

• Even use of bare wires run along walls in some cases. Shock hazard!

Many of these approaches demonstrate the early experimental nature of electrical wiring. Safety, insulation, and grounding greatly improved once rubber and plastic insulation was adopted for wiring.

Transition to Modern Romex

Romex, first produced in 1922, offered a flexible insulated wire for wiring homes. Its advantages over earlier methods led it to dominate residential wiring by the 1950s and 60s.

Benefits over earlier wiring:

• Individual copper wires are bundled together and sheathed in an insulated plastic jacket.

• Contains a grounding wire for safety, unlike many older wired homes.

• Uses rubber and plastic insulation that is safer and more durable than cloth or other organic insulation.

• More flexible and easier to install than armored cable, conduit, or knob and tube wiring.

While some very old homes still use primitive wiring methods, Romex has been the standard for wiring new construction and remodels for over 70 years. Its flexibility, safety features, and durability make it well suited to residential applications.