What type of wire system is knob-and-tube wiring?

Knob-and-tube wiring is classified as a 2-wire ungrounded system. This type of wiring system consists of two conductors: a hot wire and a neutral wire. The hot wire carries the electrical current, while the neutral wire returns the current to the electrical panel.

The system is called "knob-and-tube" because it uses ceramic knobs to support the wires and ceramic tubes to protect the wires where they pass through framing members. One of the key characteristics of knob-and-tube wiring is that it does not include a ground wire, which means it is ungrounded. Without a ground, there is no direct path for electrical current to flow safely to the ground in the event of a fault, making this old system less safe than modern wiring methods that include grounding.

Understanding these features is crucial for identifying the wiring systems in older homes and for assessing their safety and compliance with current electrical codes.