M.C Wire

[Big Guns]

When installing metalic cable with a ground wire in it. Does the cable clamp in the metalic box have to be tightened all the way or does the the cable support installed within 12 inches from box considered code compliant. The code states that the cable has to be continuous. And the armor on M.C isn't considered the main bond

 

[Smart $]

When installing metalic cable with a ground wire in it. Does the cable clamp in the metalic box have to be tightened all the way or does the the cable support installed within 12 inches from box considered code compliant. The code states that the cable has to be continuous. And the armor on M.C isn't considered the main bond

Both the clamp has to be tightened (all the way) and secured within 12" are required. It takes both to be compliant.

To serve the purpose of an EGC, interlocked (i.e. spiral wound) metal-tape-type armor of MC cable must be used in combination with the contained grounding conductor. However, the metal sheath of tube-type MC cable can be used as an EGC by itself or in combination with a contained grounding conductor.

 

[busman]

The reason is not that the armor of the MC cable is a secondary EGC. It's that the metal armor is there for protection of the cable and since it just happens to be made of metal, it needs to be bonded to the grounded box. The fitting can work both ways.

Mark