Knob and Tube Connectors

[al hildenbrand]

Re: Knob and Tube Connectors

Originally posted by Riograndeelectric:
Since when is it legal to make an extension from an ungrounded system or to add a new device or fixture that is required to be grounded.

That's the main question, isn't it?

The answer is rooted in the history of the work and the NEC in effect at the time the work was done.

The BX extensions in the photo I linked to at the bottom of the second page of this thread shows an old installation. To my eye, the material visible looks like installations I've seen that were done in the '30s or '40s. Back then, the BX was not required to be grounded in that situation. The metal sheath was great for physical protection for the fished extensions added to the original K&T. This work was inspected and approved under the NEC of the day.

Now, to be clear, I've also seen a lot of changes to existing K&T that were not legal at any time.

 

[wireman3736]

Re: Knob and Tube Connectors

I still have to disagree with you Al, I guess it's all how you interpit the code. In the 05 handbook there is a commentary following 410.18 it states, (In older installations where luminaires are replaced, the requirement to ground exposed metal parts of the luminaire is not negated simply because there is no means of grounding provided by the existing wiring system). As far as 410.18A if there was a ground then why would you want to insulate the fixture from it? I would agree if the metal base of a metallic fixture was insulated from possible contact with ungrounded conducters but I don't see that with most common fixtures that I have installed. I believe that to be the intent but it wouldn't be the 1st time I was proven wrong.

 

[al hildenbrand]

Re: Knob and Tube Connectors

Originally posted by wireman3736:
As far as 410.18A if there was a ground then why would you want to insulate the fixture from it?

I'm not saying "Don't use an existing ground."

Nothing in 410.18 prohibits using an existing ground.

I am showing that the Code allows (410.18) an ungrounded luminaire outlet to remain ungrounded in certain situations (250.110) when the conditions are satisfied and that one is not required to install a new ground, although one may install a new ground if one elects to.