Senerio: Contractor does a 100 amp to 200 amp service upgrade to a single family home. The meter, and 100 amp panel, were located in the basement. The new meter is now located outside of the garage,and a new 200 amp panel is located on the inside wall of the garage. The old panel was left in the basement as a subpanel. The contractor fed the old panel with pvc from the new 200 amp panel. In the pvc are the two ungrounged legs, the neutral,and the main grounding electrode/equipment grounding conductor(one wire which hits a lug on the ground bar{neutral is isolated} then proceeds through the panel to the water meter located a couple feet away).Here's my question. Can the main g.e.c also be used as a e.g.c? I know system grounding is different then equipment grounding, but besides by definition is there an applicible article in the code I can refer to?

cthusky,
if in fact, this is a detatched garage, then both structures would require a GEC, and GE's, and the conductor you mention bettween panels would merely be the EGC.

Sparky, no this is an attached garage.

I don't believe anything in the NEC says this can't be done. Just have to make sure you are not setting up parallel neutral paths with incorrect bonding in the sub panel.

As long as the grounding electrode conductor is continuous and the grounded conductor is not bonded to the grounding conductor, I see no problem with the installation.
Don