Introduction
Rewiring a home can be an intimidating task for any homeowner. Most of us are accustomed to modern electrical methods that utilize Romex cabling, breaker boxes, and simple on/off switches. However, prior to the electrical revolution of the late 19th and early 20th centuries, homeowners employed very different techniques for bringing electricity into their homes. Although obsolete by modern standards, learning about these historical wiring methods can provide fascinating insights into past technology. In this article, I'll highlight some of the forgotten and obsolete methods used for residential rewiring in bygone eras.
Gaslighting
Gaslights were one of the earliest forms of electric illumination. From the early 1800s up until about 1910, gaslights were widely used in homes and businesses.
Gaslights consisted of a glass globe enclosing a controlled natural gas flame. The gas was distributed through a system of underground pipes that were made from wood or metal. An above ground gasometer held gas reserves and applied pressure for distribution.
To install gas lighting, a homeowner needed access to a municipal gas supply. They would hire a plumber to route gas pipes throughout the home and mount gas lamps in desired locations. The lamps featured stopcocks to control gas flow and framers to hold the glass. Mantles or impregnated fabric increased luminosity.
Although revolutionary for their time, gaslights had drawbacks. They consumed copious amounts of natural gas, produced weak illumination, emitted fumes and heat, and posed a fire risk. The introduction of electric lighting in the late 1800s rendered gaslights obsolete. Nonetheless, they were an important transitional technology on the path toward modern electrical lighting.
Early Battery Power
The invention of the electric battery enabled some of the earliest forms of residential electric lighting. Innovators in the 1800s found that connecting batteries in series produced sufficient current to power lamps.
One of the first battery-powered illumination systems was Grove's lamps, invented around 1839 by British scientist William Robert Grove. His setup used platinum coils and diluted sulfuric acid to produce electricity. This flowed through insulated wiring to glass containers filled with rarefied gases that glowed brightly when electrified.
To install Grove's lamps, homeowners would acquire the necessary batteries, wiring, and specialized gas discharge lamps. These offered brighter, cleaner light compared to messy, flickering gaslights. However, the need to constantly service the dangerous sulfuric acid batteries was a major drawback.
Other early battery-powered illumination options included carbon arc lamps and incandescent bulbs using carbon filaments. But the hassle of replacing spent batteries and the weak light output prevented widespread residential adoption. These early electric lights served mainly as novelties for the wealthy.
DC Power Networks
The war of currents between Thomas Edison's DC power system and Nikola Tesla's AC system is one of the most famous technological rivalries in history. During the 1880s and 1890s, direct current (DC) power networks proliferated as an early means of electrifying homes.
Edison's Pearl Street Station in New York City began operating in 1882, supplying DC current to surrounding buildings via buried copper conductors. To install DC power, a homeowner would hire an electrical contractor to connect their home's wiring to the electric mains. Early DC systems operated at low voltage around 100V, necessitating thick cables to carry sufficient current.
Since DC systems could only transmit electricity about one mile from the generating plant before voltage dropped, neighborhoods needed their own microgrid power stations. While safer than gas lighting, these networks suffered from short reach, power fluctuations, and inability to step voltages up or down. By the late 1800s, AC power emerged as the superior transmission standard.
Edison Three-Wire System
Thomas Edison helped extend the viability of DC power by developing the three-wire distribution system in the 1880s. This new DC wiring method delivered higher efficiency and allowed larger coverage areas.
The three-wire system introduced a third "neutral" conduit between the positive and negative cables. Voltage on the outer lines measured +115V and -115V relative to the middle neutral line. This staggered the voltage drop versus a two-wire circuit.
To upgrade to the three-wire system, homeowners hired electrical contractors to run the new dual-voltage DC lines throughout their property. They could then enjoy double the voltage while using the same low-gauge copper wires. This system became popular for large facilities like factories, warehouses, and apartment buildings.
Although the three-wire system was an ingenious DC innovation, the inferiority of direct current for long-range transmission led to alternating current being adopted as the national standard by the early 1900s. DC grids faded away.
Early AC Power
The war of currents between AC and DC power was settled in Nikola Tesla's favor after his alternating current proved far superior for transmitting electricity over long distances.
In the late 1800s, Tesla partnered with George Westinghouse to commercialize AC power systems. They used transformers to step up AC voltage for efficient transmission over miles of cable. At the user end, step down transformers reduced voltage to safe levels for lighting and motors.
Homeowners in AC-electrified areas hired electricians to wire their homes with the newfangled AC lines. The power came from centralized generating plants instead of neighborhood microgrids. Early AC grids operated at a frequency of 133 Hz before standardizing to 60 Hz.
Compared to DC, alternating current offered major advantages for home electrification including voltage control, reduced wire size, improved efficiency, safer operation and economy of scale. AC power finally made widespread electricity adoption in homes economically feasible.
Knob and Tube Wiring
The knob and tube (K&T) wiring method was commonly used for residential electrical systems in North America from about 1880 to the 1940s. This historical technique used open wiring with insulation at connection points.
K&T wiring gets its name from the porcelain knobs that insulate and route cables through open attics or crawlspaces. Tubes protect wires that pass through walls and other structural penetrations.
To install knob and tube wiring, an electrician would carefully follow guidelines for minimum separation between wires. They routed rubber-insulated copper conductors via knobs mounted to rafters or joists. The tubes maintained safe clearance where wires passed through wood framing.
Compared to modern NM and conduit methods, knob and tube offered a more DIY-friendly approach using common materials. However, the rise of electrical loads in homes made it obsolete. K&T lacks capacity for large loads and can be fire-prone.
Old Wiring Colors
Early home electrical systems used unconventional color codes compared to modern wiring.
In 19th century European homes wired for DC power, red insulation indicated the positive conductor. The return came through a black-insulated wire. Green or bare copper meant ground.
In the knob and tube AC era, black was used for "live" or "hot" wires carrying voltage. White signified the grounded neutral return. Green still denoted grounding conductors. Red wires provided switched power to lights and other loads.
When NM cables emerged in the 1930s, a new color standard took hold. Black still meant live, but white now indicated the second "traveler" wire rather than neutral return. The neutral was bare or green.
Finally in the 1950s, the now-familiar NM cable colors became standard: black (live), white (neutral), bare/green (ground). Understanding old wiring colors helps ensure safety when working on antique electrical systems.
Armored Cable (AC cable)
Armored cable (AC) emerged in the 1920s as an early predecessor to modern NM electrical cable. Designed for versatility, AC cable combined flexible power wiring with exterior metal armor.
AC cable consists of two rubber-insulated wires wrapped with a tarred cambric cloth tape, all contained within a flexible spiral-wound steel armor. This concept aimed to provide abrasion resistance while maintaining bendability.
To install AC cable, electricians pulled the durable armored lines through walls, conduit, and other structural paths. Terminals stripped the steel wrapping, allowing connections to fixtures.
Armored cable offered a leap forward in electrical safety and performance versus old knob and tube wiring. The metallic sheathing grounded the circuit and mitigated voltage drop. While still used in some industrial settings, AC cable has been displaced in homes by PVC-jacketed NM cables.
Conclusion
Rewiring a home using obsolete techniques can certainly be challenging, but also provides fascinating insights into past electrical practices. While gaslights and DC battery power seem hopelessly outdated now, these technologies pioneered modern illumination. Knob and tube wiring and armored AC cable were important transitional methods on the path to today's convenient AC-powered NM cables and breaker boxes. I certainly don't recommend abandoning modern wiring techniques, but I do think it's valuable to learn from our electrical history. Hopefully this article provided some illumination on this often overlooked topic!