Knob and Tube Wiring Process

In this type of installation – known also as an open wiring system – two copper conductors (hot and neutral) run within walls or ceiling, and everywhere they pass through a joist or a stud, they do so inside a porcelain tube. This tube was designed as an insulator between wire and wood and as a protective sleeve against compression from house settling. When a conductor entered a device, it was protected by a cotton-made insulating sleeve called a loom.

The knobs were also of porcelain material, shaped cylindrical, and nailed down along the desired path of the wire to support it and insulate it from the surrounding wood.
Back then, this was considered innovative technology, and it met the energy needs of a typical household. Following World War 2, the sudden and wide availability of electrical appliances made the (K&T) installation not suited anymore.

There are many reasons why this installation is not suited for our modern infrastructure.

Outlets rewiring

Lights rewiring

Switches rewiring

Circuits rewiring

Technical Details

In a modern house, the electrical service can range from 100 AMPs to 200 AMPs. This makes it possible to supply modern life appliances, like, hot tubs, heat pumps, car chargers, and electric stoves, while the common size service of 60 AMPs used with (K&T) installation, limits the possibility of integrating all these appliances in your home.

With (K&T) installations, the panel size was generally smaller than today’s panel sizes. That means a limited number of circuits compared with modern panels. If the need arrives for a new circuit, it is common for homeowners to double tap on an existing circuit. The new current load will trigger the breaker and if a higher amperage breaker is installed to avoid the tripping, the circuits will overheat creating a fire hazard.

Another shortcoming of (K&T) is the inexistence of ground wire. This shortcoming makes the (K&T) installation extremely hazardous for the kitchen, bathrooms, laundry, and outside spaces as there is no way to protect against ground faults. In the event an appliance’s outer case becomes energized, there is no path to de-energize it.

This open wiring system was designed to allow heat to dissipate in the immediate air thus making the installation sensitive to thermal insulation. If the insulation surrounds the wires, the heat is trapped making it hard to escape, which increases the risk of fire. The 2008 NEC prohibits the use of thermal insulation over (K&T) installation although some jurisdictions allow it under strict conditions that must be met.
If your house has a (K&T) installation, we can provide an estimate and subsequently a timely rewiring to minimize the disruption involved with such undertaking.

Knob and Tube Wiring in Seattle

Becoming the owner of an older, heritage style home can be thrilling, but also incredibly challenging. If your house was built prior to 1950, you’ll need to consider the type of wiring the home has, for instance, copper, aluminum, or knob and tube (k&t).
One of the main differences between modern wiring and the old knob and tube, is that there is no ground wire. Therefore, this type of wiring cannot accommodate any electrical items with three pronged plugs, and the risk of shocks and fire is much greater. Also, the black and the white wires run separately, while in more modern wiring, you will see that the black wire, the white wire, as well as the ground wire, are all enclosed in a single cable. We offer a complete service for the knob and tube wiring replacement and installation in Seattle and the surrounding areas. Get your older house a modern wiring!