The armor of AC Cable,(0NLY IN CONJUNCTION WITH THE INTERNAL BONDING STRIP), provides an adequate, low impedance, equipment grounding path.
This is not the case with MC cables of the interlocked (spiral wound) armor type. In that case, as CT said, the configuration of the armor will choke the fault current. Therefore, with common MC, the insulated grounding conductor is required to adequately serve as the EGC.
[This message has been edited by Redsy (edited 03-26-2003).]
