Permitting new knob-and-tube wiring

[david shapiro]

The NEC explicitly permits running new concealed knob-and-tube (K&T) wiring for extending existing K&T circuits. In what seems to me anomalous language, it reduplicates part of 90.4 by saying the AHJ may permit K&T for other wiring by special permission. I suppose this could be for a new circuit, or even for extending a non-K&T circuit. (At least there you'd have a good place to pick up a ground wire.) So it is writ.

Some years ago, chatting with a Southron colleague, I was told that in his jurisdiction K&T was permitted simply because they had enough flooding that they preferred a wiring method that would dry out and be usable again without having to worry about contaminants bridging between conductors the entire length of a cable or raceway. Who? When? I don't remember.

Does any of you know of jurisdictions where this is or has been the case, perhaps as a local amendment in the adopting legislation?

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[Jerry Peck]

Does any of you know of jurisdictions where this is or has been the case, perhaps as a local amendment in the adopting legislation?

Not me.

Why someone would extend a K&T circuit with new K&T is beyond me, material cost, labor cost, and safety are three reasons not to.