Using MC Armor Jacket as Ground?

[johnestan]

My 1927 house has metal boxes that are grounded. I pretty sure its only grounded through the MC armor jacket. I do not see an separate ground wire or a bonding strip. Can I use the armor jacket as a ground? The armor is magnetic so its made of steel and not aluminum. If it's not an acceptable ground path, how to I ensure that switches and outlets don't ground through the screw. Are there special non-self-grounding outlets and switches I need to use. Thanks.

https://imgur.com/a/kO4ohN0

 

[Dennis Alwon]

You probably have ac aka bx cable. Some are bonded thru the cable with a metal strip inside the cable which you would not see from the pic. If it doesn't have the strip then you cannot use it as an equipment grounding conductor.


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[augie47]

I might add it would be prudent to have a knowledgeable electrical contractor take look at the existing system.
Considering the vintage of the installation, as Dennis states, it is likely an early AC cable, brand name BX, and the early versions had no bonding strip and it was possible, in a short circuit situation, the outer jacket of the cable becoming a "heater" and fire danger.
Some jurisdiction banned the use of that cable for a while until the manufacturing process addressed the issue.