Q. What is the problem with knob and tube wiring?

Q. What is the problem with knob and tube wiring?

A.  Homes built from the late 1800s to the 1940s often have knob and tube electrical wiring. This is where electrical wires anchored by ceramic insulating knobs pass through tubes placed inside holes drilled in the joists of the house. Although it is still considered safe in the right applications, there are a few issues with knob and tube wiring that homeowners should be aware of.

1) Insulation cannot touch the wires, because the heat from the wires cannot dissipate.

2) Knob and tube wiring does not provide a grounding wire. Even if two-slot outlets are replaced with three prong outlets, there is still no third wire which protects against electric shock. One potential way to address that is to replace every two prong outlet with a GFCI outlet.

3) One of the most common issues with knob and tube wiring is incorrect modifications. Because it is easily accessible, some homeowners make their own updates/repairs and do not splice the wire correctly or they make inadequate, unsafe modifications.

4) Knob and tube wiring is no longer used in homes because it doesn’t carry the same electrical capacity that modern homes require. Modern appliances and air conditioning use much higher loads of electricity than the wiring was originally designed for (usually 60 amps). Installing higher amp fuses to match the increase in electricity use will cause the wires to overheat.

If you are considering a home with knob and tube wiring, it is crucial to have a qualified electrician evaluate the wiring and make any and all updates/repairs deemed necessary. Usually most or all knob and tube wiring will be replaced which can become an expensive project.