Knob and Tube Wiring. A simple explanation.

N Aville KandT

The first wiring method used in houses was knob and tube wiring. This was used from the late 1800’s to the 1930’s.

This method of wiring was intended for use with very light electrical loads. It was installed with the intention of having free air space around the conductors for cooling. Thus, installing insulation in an attic around the wiring can be dangerous, causing the wiring to overheat and thus a fire.

The problems we see with this very old wiring method. Are multiple, the first being heat build-up when the wiring is insulated around in an attic, the second being improper splicing of the wire. This splicing can occur in junction boxes that are not installed safely. It can also occur in splices that are made without junction boxes. These open spaces are an obvious fire hazard since there is no junction box to contain heat buildup and burn.

This method of wiring is also incompatible with today's modern electronics since there is no electrical ground wire for the dissipation of surges. These surges can be caused by lightning or caused by excessive power surges from the power company.

We often find open knob and tube conductors in basements and attics. This is particularly dangerous in basements and can lead to shock or electrocution by someone coming in contact with an energized wire.