Good Wire, Bad Wiring

An original service of knob-and-tube wiring, if properly installed, is and can remain a safe electrical system. Left alone, it would satisfy the electrical demand for which it was designed without any problems.
When it isn’t left alone, or when the loads increase and stretch the system’s capacity, the problems and hazards begin. Add-ons are pretty easy to spot, especially those done by homeowners. Dead giveaways include …

• Sloppy installation.
• Loose, unsecured wires.
• Wires running across the edge of floor joist rather than passing through them in unfinished basements.
• Improper taping at connections through the use of unapproved materials such as masking or adhesive tape.
• Mixing two different gauges of wire on the same circuit.

Other issues include worn and frayed insulation and brittle wire ends where they are attached to loads or switches. This problem is exacerbated as the wire ends get bent and unbent when switches, receptacles, and light fixtures are replaced over the years due to general wear and tear or the desire for something new.