The Good with Knob and Tube

In theory, Knob and Tube will dissipate heat better than modern Romex cable due to it being an open-air installation. This allows for higher amperage fuses to be used.

Due to the open-air installation, it is less likely to be damaged by nails.

More knowledge and skill were required to install these systems. The layout for drilling, the splicing techniques, the soldering, and the taping of the splices shows the higher degree of skill required.

The Bad with Knob and Tube

  • Over time these systems were altered. As homes have been remodeled or additions made the systems were extended to supply electricity. The main system was not designed for the extra needs of a modern home.
  • Some of the systems used bare conductors that are not intended to be in direct contact with insulation. If in contact with insulation, overheating will occur resulting in a potential fire hazard.

Incorrect Splicing

  • Splicing of Knob and wiring to Romex cable is typically done incorrectly. To make a correct splice, 6 inches of cable must enter the junction box. If only one junction box is used there will not be enough cable. Two boxes must be used to correctly make the splice.

Is Knob and Tube Wiring Safe?

  • Knob and Tube wiring systems are usually not safe due to the expansion of the system and incorrect splicing.
  • If the system is undisturbed and has not been altered it should be relatively safe.
  • When Knob and Tube is discovered in a home it should be evaluated by a qualified electrician to determine if it is safe to use or if it will need to be modified or replaced.