How Early Electricians Lit Up Homes with these Rare Historical Wiring Methods

Before the widespread availability of electricity, homes were lit with candles, oil lamps, and gas lights. The invention of the incandescent lightbulb in 1879 paved the way for the electrification of homes, but actually wiring homes presented some unique challenges in the early days of electricity.

The Knob-and-Tube Wiring System

The knob-and-tube wiring system was commonly used to wire homes in North America from about 1880 to the 1940s. This system involved running electrical wires through free air, supported by ceramic knobs and tubes:

• The knobs were nailed or screwed to walls, floors, and ceilings to hold the wires in place and prevent them from touching each other or the framing members.

• The tubes were used to protect wires as they passed through framing members.

Some key advantages of knob-and-tube wiring included:

• Open air design prevented overheating.
• Wires were separated from each other and combustible materials.
• System was expandable and easy to work with.

However, it had some drawbacks such as:

• Fire hazard since insulation rubbed off over time.
• Unsafe for modern high-power appliances.
• Difficult to retrofit into existing homes.

Over time, knob-and-tube wiring was phased out in favor of safer, insulated wire systems. However, it is still possible to find knob-and-tube wiring in older homes today.

Early Armored Cable

The first insulated electrical cables specifically designed for indoor use were developed in the 1890s. One early type was BX armored cable (also known as BX or armored flexible cable).

BX cable consisted of:

• 2 or more copper conductors wrapped in rubber insulation.
• Layers of tarred jute or hemp to pad and bind the wires.
• An armor wrap of flexible steel tape.
• An outer jacket of rubber or treated cotton.

The armor provided protection from physical damage while also acting as a grounding conductor. BX cable was more expensive than knob-and-tube wiring but much safer and easier to install. It was commonly used for lighting branch circuits in homes.

Conduit Wiring

Conduit wiring systems also emerged in the 1890s as a safer alternative to open wiring methods. This involved running wires through rigid metal conduits.

Some key advantages of conduit wiring included:

• Conduits protected wires from damage.
• Provided protection from fires and shocks.
• Wires could be pulled through conduits easily for upgrades.

Early conduit was made from steel but was heavy and difficult to work with. The introduction of lightweight thin-walled electrical metallic tubing (EMT) in the 1920s made conduit systems much more popular.

By mid-century, conduit wiring had displaced knob-and-tube as the standard wiring method for new construction. Flexible metal armored cable was also widely used.

Transition to Modern Wiring Methods

After World War II, there were major improvements in electrical wiring:

• Plastic insulation replaced rubber, paper, and cloth.
• PVC and metal conduit offered a lightweight, flexible option.
• NM cables (non-metallic sheathed cables) emerged as an easy wiring method.
• Circuit breakers began replacing fuse boxes.

These more efficient, safer wiring methods were adopted into the National Electrical Code in the 1960s and 70s. While knob-and-tube and armored cable continued to be used in older homes, most new construction utilized the latest wiring techniques.

Today, plastic-insulated NM cables wired through PVC conduits and connected to circuit breaker panels are standard. But knob-and-tube and armored cable can still be found in homes that pre-date these upgrades. Understanding these early wiring methods is key for homeowners and electricians working on renovating heritage homes.