OK, I will try to be more clear.
I have a three conductor with additional ground conductor cable going
between panels. In the main panel, fed from the road, the neutral and
grounds are equal, with the normal configuration of the neutral and grounds
bonded to the panel frame, and the whole thing grounded to a ground rod and
to the neutral coming in from the pole.
In the sub panel, which was the house's original panel, the neutral is not
bonded to the frame of the panel, and there is a separate grounding lug
connected and bonded to the frame of the panel.
Now for what the cable coming from the main panel is connected to. Remember
that it is two hot wires (insulated) a neutral wire (insulated) and
grounding wire wrapped as individual strands around all of the insulated
conductors, and all of it covered in plastic sheathing. The two hot wires
are of course connected to the two breaker busses, the neutral is connected
to the insulated buss bar and has all of the neutrals coming from the house
circuits connected to it. The buss bar that is bonded to the frame has all
of the ground wires from the circuits going to it, and is connected to the
ground wire in the service feed cable.
This additional ground wire the inspector wanted was to be a #6 bare copper
wire connected at the main panel (service entrance) onto the ground/neutral
buss and then run to the sub panel and connected to the ground buss. (which
is bonded to the frame)
I believe Clair read my description correctly, and that the two #6 bare
copper and the ground conductor in the cable are connected to the same
things in each panel, and they are parallel, and that the #6 is indeed above
code and unnecessary.
If it is necessary, I sure would like to know the reasoning behind what it
does, and why it is necessary.
OK, go at it!