Separately derived multiwire branch circuits

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raheloftin

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My query is as follows:
I have two 3 phase transformers, A & B, with a 208/120 volt secondaries.

Each transformer supplies a separate panelboard A & B respectively.

Each panelboard is grounded to the same bus bar in the electrical room which then goes back to a common counterpoise building grounding system.

Together, the 2 panelboards have branch circuits to standard receptacles mounted in a common metal enclosure.

If a phase conductor and neutral from Panelboard A supplies one receptacle and a phase conductor and neutral from Panelboard B supplies an adjacent receptacle, do I need a separate ground/bond back to each panelboard if the circuits are in the same 50 foot MC cable?
 
raheloftin said:
If a phase conductor and neutral from Panelboard A supplies one receptacle and a phase conductor and neutral from Panelboard B supplies an adjacent receptacle, do I need a separate ground/bond back to each panelboard if the circuits are in the same 50 foot MC cable?

How would you get the circuits into one MC cable in the first place?

At any rate, no, they could share the same EGC. However, at some point, the circuits seperate, and there would be a seperate EGC with the branch circuit back to it's own panelboard.
 
One EGC should suffice for the home-run, but I guess you'd want to have an EGC back to both panels from the point where the two circuits join together.

That way, if either panel were to somehow "disappear," the remaining circuit would still retain its EGC. Can you find a two-plus-two-conductor-plus-two-EGC MC cable?
 
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