Cable - re-identifying white as EGC ?

[TwistLock]

Conditions / space necessitate using MC, to run a circuit from a Technical Power panel. This branch circuit needs an iso ground.
Does 250.119(C) allow me to re-identify the white wire in 12-3 MC as the Isolated ground ?
( fwiw - Southwire etc. do list iso ground with egc in 12-2 MC but my local suppliers always tell me it has to be special ordered ).

 

[macmikeman]

Remove insulation at both ends of the exposed wire? Use the now bare wire as the regular ground and the green insulated conductor as the isolated one.

 

[LarryFine]

Remove insulation at both ends of the exposed wire? Use the now bare wire as the regular ground and the green insulated conductor as the isolated one.

I did that with the red wire in 12-3 MC for a 120v IG circuit.

 

[roger]

You could also use 12/2 HFC or 12/2 MC-AP. The sheath would be the EGC and the insulated green could be the iso EGC

 

[don_resqcapt19]

Conditions / space necessitate using MC, to run a circuit from a Technical Power panel. This branch circuit needs an iso ground.
Does 250.119(C) allow me to re-identify the white wire in 12-3 MC as the Isolated ground ?
( fwiw - Southwire etc. do list iso ground with egc in 12-2 MC but my local suppliers always tell me it has to be special ordered ).

There is a conflict between 200.7 and 250.119(C). In my opinion the more specific rule in 200.7(C) applies and does not permit you to re-identify a white as an EGC, but it does permit you to re-identify the white as an ungrounded conductor.
I would permit you to re-identify the white, as the isolated EGC, but the code really doesn't.

 

[TwistLock]

There is a conflict between 200.7 and 250.119(C). In my opinion the more specific rule in 200.7(C) applies ...

I can't quite get the two of them to match up either and I think general consensus agrees with you. Though it might only be considered more of a raised eyebrow and easy to get a variance on it in certain situations like you say.

You could also use 12/2 HFC or 12/2 MC-AP. The sheath would be the EGC and the insulated green could be the iso EGC

Completely escaped me (or subconsciously I didn't want to buy a full roll just for 30ft.) That's a great suggestion.

 

[curt swartz]

Standard 12/2 MC-AP only has 2 insulated conductors.

For a 30' run how about EMT or Flex? For the first part of my career MC and AC weren't used in my area.

 

[TwistLock]

Standard 12/2 MC-AP only has 2 insulated conductors.
For a 30' run how about EMT or Flex? For the first part of my career MC and AC weren't used in my area.

That's correct, but 12/2 HCF was also suggested. MC just allows me to get around some very tight spaces efficiently.