In the early days of home wiring installation, a system known as knob-and-tube wiring was predominantly used. Although knob-and-tube wiring disappeared from new home construction in the 1950s and 60s, there are still numerous homes in the United States with this particular configuration.
That’s why it is important to be informed about knob-and-tube wiring, including understanding its installation characteristics and the difficulties it can present homeowners. Below is more information about knob-and-tube wiring and what you should know if it’s used in your home.
Today’s residential electrical wiring consists of two or three strands joined together in a single sheath. One of the strands is the hot connection, and then there’s a neutral wire that returns current to the source. In the case of three-stranded wiring, the third wire is a ground connection.
Knob-and-tube wiring is different in how two individual strands of wire are routed on paths that may or may not be parallel. Each strand is supported by ceramic knobs attached to structural supports, such as joists and studs. In addition, ceramic tubes are used to make wire tunnels through wood.
The knobs keep the wire away from wood and other flammable materials. They also provide attachment points for transitions, such as 90-degree turns or reversals. Tubes provide a clean path for wires, and they keep them from rubbing against other materials as they pass through the opening.
Another key difference between modern residential wiring and knob-and-tube wiring is the manner in which wires are joined. Modern electrical codes require that two and three-stranded wires be joined together in an electrical junction box. However, knob-and-tube wiring junctions are formed by splicing, soldering and taping the connections with cloth tape.
It’s important to recognize that knob-and-tube wiring isn’t inherently unsafe due to its design. Even though knob-and-tube wiring is no longer permitted in new construction in the United States, it is still utilized in construction throughout the world. If a knob-and-tube installation is performed correctly, then it is as safe as other types of wiring configurations.
However, there are some issues that cause concern for homeowners who have an interest in preventing house fires and other damage. There are three primary concerns that emerge from using knob-and-tube wiring: age of the wire, lack of ground connections and insurability concerns.
Age of the Wire
In the first situation, old wiring can be plagued by several specific problems, such as brittle or cracked insulation. Insulation deterioration is a cause of electrical shock and may even cause a fire when accidental contact results in short-circuiting. In addition, the slightest movement or disruption may cause damage that isn’t discovered until it’s too late.
Lack of Ground Connections
Another problem posed by knob-and-tube wiring is the lack of ground wires. Ground wires safely divert stray electrical currents into the ground, and they prevent electrical shocks as a result. Knob-and-tube wiring doesn’t allow for this safety precaution and can leave a home vulnerable as a consequence.
Finally, knob-and-tube wiring is frowned upon by home insurers and may prevent your home from being covered. Even though safety doesn’t need to be compromised when living in a home with knob-and-tube wiring, some insurance companies have blanket prohibitions and may encourage you to look elsewhere for coverage.
If you have questions or concerns about your home’s wiring configuration, be sure to contact In Phaze Electric Inc. for help. Our expert staff can resolve your concerns quickly and help ensure your home is kept safe and sound by installing modern wiring and performing approved repairs on existing systems.