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What Is Knob and Tube Wiring?

Knob and tube wiring is an early regulated form of electrical wiring used in buildings. It was common practice to use this method in North America from roughly 1880 to the 1930s. Single-insulated copper conductors were run inside walls and ceiling cavities by means of stud and joist dill-holes that relied on porcelain insulating tubes for protection. Support placed along the length of the wiring was provided by porcelain knob insulators that were nailed-down.  Due to the high installation costs, different interior wiring systems were eventually utilized. Today, knob and tube wiring is only permitted to be installed in highly specific circumstances outlined by the National Electrical Code, including particular agriculture and industrial atmospheres.

The cylindrical knobs utilized were usually nailed straight into the floor joists or wall studs. To keep them from breaking during the installation process, most had a leather washer to act as a cushion. The electrical wires would wrap around the knob and secured in place with tire wires, which allowed the knob to be a permanent anchor for the wire. The purpose of the ceramic tubes in the holes of the wall studs and floor joists was to ensure the wires never made contact with the wood framing and so the wires would not be compressed by the wood when the structure settled. A flexible woven insulating sleeve referred to as a loom, was used as an additional agent of protection. It would cover insulated wire where a wire crossed over or under a separate wire, and when a wire would enter an enclosed metal device. The original insulation slip was crafted out of cotton cloth saturated in asphalt. Ultimately, rubber became the popular choice of loom. These distinct characteristics make it is easy to identify this style of wiring.

Numerous historic homes in America rely on knob and tube wiring. However, this outdated type of wiring is dangerous and poses a serious threat to the home and occupants.  While the wiring is functional, it is not equipped to handle the required electricity that is necessary for modern devices. As a result, the knob and tube wiring experiences regular overload which can lead to a fire.  Another concern is that loom can deteriorate as it ages, and expose the wires. The inadequate durability causes the breakdown, sagging, and stretching of components, which causes them to make accidental contact with nearby materials. This can produce serious electrical and fire hazards. Another safety issue is that the wiring is not suited for moisture rich environments, such as bathrooms, kitchens, laundry rooms, and outdoor areas. Knob and tube wiring does not utilize grounding, so it only provides a neutral and hot wire. This creates a situation where fluctuations and surges in voltages have nowhere to travel which leaves the belongings, the home, and the inhabitants exposed to the dangers of shock and fire.

At Rose Brothers & Sons Electric, we are available for residential, commercial, and industrial electrical projects. We work on new builds, historical homes, and remodeling projects to install circuits, transformers, and primary service. We pride ourselves on doing work that is done correctly, and is a permanent solution to the electrical problem. Unlike other electricians, we are not in the business of fast repairs that are merely a temporary fix. We are located in Walton, KY and provide service to Northern KY and Cincinnati. Call us today to schedule an appointment.

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