Can I use the existing 10/3 steel armored cable as feeder for a 240v 30 amp subpanel in my garage (detatched)?
That's 3 wires and a grounded metal jacket. 2 hots (red and black) which connect to a double 30a breaker at the main panel, along with a neutral wire(white) which is bonded to the main panel.
I've seen similar things discussed here so I know I'm missing a wire somewhere. The Does not the metal jacket substitute for the lack of a bare ground wire? Suppose I use a ground rod at the subpanel. Any reason not to ground cable at both ends? Does a 30 amp GFI at the main panel mitigate concerns about the missing wire (?) be it green or bare copper? That's a lot of questions so I'll summarize. How can I di this without replacing the 10/3 armored feeder?
Best Answer
Armored cable can't defend itself from the rain
You'll need to re-run this cable in order to meet Code. While you have enough wires there for your proposal as the armor on modern type AC can be used as a grounding conductor as per 320.108, AC cable can't be run in damp or wet locations (such as outside attached to a fence) as that violates 320.12 point 2. In fact, I would not be surprised if the cable already has water in it, or is even rusting away as we speak, depending on how long it's been out there.
Replacing the cable with a PVC-jacketed (wet location rated) type MC or MCI-A cable is your best bet here as a result.