What is the primary concern with knob-and-tube wiring systems?

The primary concern with knob-and-tube wiring systems is the lack of grounding and the potential for overheating. Knob-and-tube wiring, which was widely used from the late 1800s to the 1940s, does not include a ground wire, making it less safe by today’s electrical standards. This absence of grounding means that electrical faults or surges might not be diverted safely, increasing the risk of electric shock. Additionally, when these systems are overloaded with modern electrical appliances and devices, the wires can overheat, leading to potential fire hazards. The older insulation around the wires can also deteriorate over time, further increasing the risk of overheating and electrical failures.

While excessive energy consumption, inadequate lightning protection, and insufficient wire sizes for modern appliances are all issues that can arise with older electrical systems, they do not capture the primary and most critical risks associated with knob-and-tube wiring as effectively as the lack of grounding and potential for overheating do.