The answer is, no, this is not permitted as in a TN-S or TN-CS Network, the only place you're allowed to connect (bond) the Neutral and the Earth (Ground) is in the main service panel fed by the utility. Since the metal conduit carries the ground, there's no need for any ground wires, therefore no need for any ground bus. " Note that nobody puts in metal conduit. So if you are DIYing electrical and got all your knowledge. The detached garage sub-panel, which used to be the main panel, is properly grounded with number #6 copper and is connected to an outside ground rod. EXISTING LOADS: My detached garage has a small 240 V compressor, 4-120 V breakers for lights, receptacles, gate & carport. The grounding wire from that one circuit is just attached to the back of the sub panel with a green screw, since there is no ground bus. There is no ground bus bar present.
[PDF Version]