You need to connect the ground wire from the main panel to the grounding bar in the subpanel. This provides a fault path back to the main panel. The grounding electrode a completely separate entity. You need both, and both should connect to the grounding bar.

And there is no reason to use a GFCI breaker to feed the panel, just use GFCI receptacles.

Thank you normel. Much appreciated. I will make sure that I include a GFCI receptacle in each circuit in the shed. Do you think that two 8ft grounding rods are necessary at the shed? I dread to think how hard it's going to be to drive an 8ft rod into the ground, even with a sledgehammer.

So I connect the grounding rod at the shed to the sub-panel ground (I don't actually have a ground bus in the sub-panel but it sounds like it would be a good idea)and also connect the ground wire from the main panel to the same point - excellent. Thanks for responding so quickly.

"I don't actually have a ground bus in the sub-panel but it sounds like it would be a good idea"

It's a little more than a good idea. It's required, as the neutral and ground buses must be separated in subpanels

Thanks bigbird. I'll go pick one up from the hardware store. I had joined the ground wires using a wire nut, keeping them separate from the neutral bus which is insulated form the sub-panel case but it would be safer to have an actual bus I'm sure. This forum is great!

You need the grounding bar to be attached to the panel enclosure so that they are electrically bonded (assuming the enclosure is metal).

Yes, the sub-panel is metal. I plan to take the bonding strap inside the panel to the ground bus and then hook all the ground wires and the grounding bar (rod) to the ground bus independently of the neutral bus.

Why is it necessary to have two grounding bars(rods)more than 6ft apart (per Tom's instructions for wiring a sub-panel)? Is this overkill?

Why is it necessary to have two grounding bars(rods)more than 6ft apart (per Tom's instructions for wiring a sub-panel)? Is this overkill?

I'm not sure, and hopefully an RKI will chime in, but IIRC it has to do with real-world data on LIGHTNING STRIKES...? =:O ... or it could just be part of the IBEW full-employment plan... ;')

Saw this post elsewhere:

"At the shed panel you need to have the neutral bar and all neutral wiring together isolated from the grounds. The ground needs to all be on one bar and attached to the panels metal enclosure. Only back at the first means of disconnect ( where the main breaker for the house is located) do the ground conductor and neutral conductor tie electricaly and physically together. You don't have to have a ground rod at the shed. But it dosen't hurt. It should only be tied to the ground bar not the neutral bar. Should a lighting strick hit the ground or shed it will look for the shortest path. And a extra ground rod will help in that situtation. If your neutrals and grounds are made up correctly then they are electrically tie together thats what keeps them at the same potential. It's when telephone and cable tv companies drive their own rod and do not tie or use the service ground is when you have problems. But you did the correct thing you ran a 4 wire feed to your shed. And by doing that grounds and neutrals are kept seperate."

Separate structures require additional ground rods.

The only way you can do without a grounding electrode at a separate structure is if you run a single branch circuit. When you run feeders to a subpanel, a grounding electrode is required.

If you can satisfy the 25 ohm max resistance with one ground rod, then one is all you need. Most will not meet that, so two are required.

Thanks to all for the answers to my questions. I believe I'm ready to get this job wrapped up.