Correct way to extend BX cable

[hbiss]

Same thing would have happened with MC then. Maybe the answer is to have a bare equipment ground in any metal flex and it (the EG) would be in contact with the cable armor.

No. With an EGC there would be an end to end ground even without the armor. What I'm assuming from the story was that the armor separated in half breaking the EG. Any Greenfield longer than 6 feet has to have an EGC run with the conductors.

But this whole story sounds fishy to me. Sprinklers? Fire system?

-Hal

 

[electrofelon]

No. With an EGC there would be an end to end ground even without the armor. What I'm assuming from the story was that the armor separated in half breaking the EG. Any Greenfield longer than 6 feet has to have an EGC run with the conductors.

But this whole story sounds fishy to me. Sprinklers? Fire system?

-Hal

It certainly depends on the specifics. My interpretation is it sounds like an ungrounded conductor shorted out on the flex.

 

[Joethemechanic]

It certainly depends on the specifics. My interpretation is it sounds like an ungrounded conductor shorted out on the flex.

I believe it was a UGC shorting out on a sharp edge of the flex.

So if it shorted in the middle, you'd still have a current flow through the flex to each box. The fact that the boxes are at the same potential means nothing as far as that circuit path is concerned.

But I'm still thinking a bare ground would have made a low enough impedance path to trip the breaker

Built in 1969. I wonder what the breaker panels were?