Article 394 Concealed Knob-and-Tube Wiring

I. General

This type of wiring is a single insulated conductor using knobs, tubes, and flexible nonmetallic tubing for support and protection.

II. Installation

It can be used only to extend an existing installation or elsewhere with special permission from the authorities having jurisdiction and in hollow spaces of walls and ceilings and unfinished attic and roof spaces (refer to Section 394.23 in the NEC®).

It is not allowed in commercial garages, motion picture studios, classified hazardous locations, theaters and similar locations, or in hollow spaces of walls, ceilings, and attics under certain conditions.

III. Construction Specifications