How the BX Armored Cable System Revolutionized Home Wiring in the Early 20th Century

Introduction

The early 20th century was a time of rapid innovation and change, especially when it came to electrical systems and wiring in American homes. One of the most important developments was the invention of BX armored cable, which provided a flexible, durable, and safe way to wire buildings for electricity. In this article, I will explore the origins of BX cable, how it changed home wiring, and why it was such an important innovation.

The Dangers of Early Electrical Wiring

In the late 1800s and early 1900s, electricity was just beginning to be adopted in homes across America. However, the wiring methods and materials used at that time were extremely hazardous:

• Knob and Tube Wiring - This involved running wires through the wall cavities and securing them to knobs along the framing. The insulation on these wires was basic rubber or cloth wrappings which could easily crack or fray over time.

• Conduit Wiring - Rigid metal conduits were also used to protect wires running through walls. But they were bulky, hard to install, and conducted electricity if there was a fault.

• Open Wiring - Some homes simply had electrical wires run across walls and ceilings unsupported. This led to sagging wires and loose connections which were a fire hazard.

These early electrical systems resulted in insulation breakdowns, short circuits, and fires. It was clear a safer and more reliable wiring method was desperately needed.

The Invention of BX Cable

In the early 1900s, an inventor named Herbert G. Harvey patented a new armored cable design that would come to be known as BX.

Key Features of BX Cable:

• An inner wiring assembly with rubber-insulated conductors
• Layers of tar-impregnated paper insulation
• An interlocked steel armor wrapping around the cable
• An outer PVC or fabric sheath

This innovative design made BX highly flexible while also protecting against mechancial damage. The steel armor grounded the cable and prevented electrocution hazards. The many layers of insulation resisted heat, moisture, and fire.

BX cable was a landmark invention that pioneered modern armored wiring cables still used today like MC (metal-clad) and AC (armor-clad) cables.

How BX Cable Changed Home Wiring

BX cabling was quickly adopted for wiring homes and buildings because it offered major advantages over previous methods:

Safety

• The steel armor prevented electric shocks and contained faults.
• Multiple insulation layers resisted overheating and arcing.
• It was vermin-proof and flame-retardant.

Durability

• The flexible steel armor protected against mechanical damage.
• It did not crack and dry out over time like rubber/cloth insulated wires.

Ease of Installation

• BX could be routed through walls and ceilings easily.
• The armor eliminated the need for conduit piping.
• Stranded wires made connections simple.

The dominance of BX Wiring

By the 1920s, BX cable was the dominant wiring method used in American homes and small commercial buildings:

• Ubiquity - It could be purchased from any electrical supplier and most electricians worked exclusively with BX.

• Code Acceptance - The National Electric Code began recommending BX over open wiring in new construction.

• Innovation - New tools like armor-sheathed cable cutters were invented to facilitate BX installation.

• Savings - Homeowners saved on installation costs by using BX instead of conduits.

• Safety - Insurance companies encouraged BX wiring, especially because of fire prevention.

For the next 50 years, BX armored cable would be the wiring method of choice for a vast majority of homes and small businesses across the United States.

The Decline of BX and Legacy

By the 1970s, updated electrical codes began requiring different wiring methods for new construction:

• Nonmetallic Cable - Plastic-sheathed cables like NM (Romex) became prevalent as copper prices rose.

• Grounding Issues - Codes began mandating ground wires, which BX did not contain.

• Safety Improvements - New insulation materials and circuit breakers reduced electrical fires.

Today, BX is no longer used in most new construction. However, due to its durability, there are still many old homes and buildings wired with original BX installations.

The BX armored cable system revolutionized home wiring and construction in the early 20th century. It paved the way for safer and more reliable electrical systems that were essential to bringing electricity into everyday life. BX represents an important milestone in construction innovation and remains a testament to the ingenuity of early 20th century inventors and engineers.