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[Debbie Dunkley]

A key to understanding both OSHA regs and the NEC is to pay careful attention to the section a given quote is in-our corporate safety director catches me on this from time to time as OSHA regs for construction are different than for industrial maintenance.  The particular quote Deb referred to is part of the construction regs.

Another key is term definitions-chapter 100 in the NEC, and often part of OSHA regs.

Grounding is covered in depth in chapt 250 of the NEC-but the recomendations in this thread will get you to the same place and are more down to earth for the laywoman.

Yes - I should have investigated further than I did... I was just so happy to find what I thought was relevant to me.

[Mike Sokol]

The advice I get here has never led me down the wrong path yet.....

Maybe the wrong career path, but never the wrong technical path....

[Mike Sokol]

Could someone clearly explain the exact purpose of the ground rod other than lightning protection?
It obvious that if genny chassis and other metal structures are bonded, then there is a path for faults to trip a breaker.
Unlike the power grid, the genny has no reference to earth, right?

The main purpose of the ground rod is two-fold. It is indeed important in lightning protection to help prevent side-flash. That when the lightning bounces around inside of all your gear and finds lots of separate paths to earth. The second purpose is to provide a ground fault path that will trip a GFCI in the event of a hot-to-earth failure in a piece of equipment. The best example I can think of is dropping an electric drill into a puddle of water. Without a path to gear ground at the generator, the GFCI won't develop any fault currents and won't trip. While that sounds like a good thing, you can now have a local ground plane energized with up to 120-volts above earth potential. And that's exactly why you want to earth-ground your generator when it's feeding multiple things, like a stage, lighting, FOH console, etc... You don't want a failure at the console to energize the entire backline of the stage. And remember as noted earlier that an earth-ground is NOT a neutral bond. The neutral bond is what supplies the low-impedance path to trip the circuit breakers in the event of a chassis-to-line short. A typical ground rod will have an impedance to ground of up to 100 ohms, but really should be less than 25 ohms to meet all code requirement. The ground-neutral bond impedance needs to be less than 1 ohm to meet code. That's so it will quickly trip a circuit breaker in the event of a short to chassis.

[Ray Aberle]

Maybe the wrong career path, but never the wrong technical path....

People can have a career doing audio?!? Man, I gotta get myself on that gravy train!

[Debbie Dunkley]

Maybe the wrong career path, but never the wrong technical path....

LOL.....this business is not for the faint of heart.

[Tim McCulloch]

People can have a career doing audio?!? Man, I gotta get myself on that gravy train!

"I have no love of stages or roofs but they pay for this little hobby I have called audio."  - another company owner.

[Dennis Wiggins]

"I have no love of stages or roofs but they pay for this little hobby I have called audio."  - another company owner.

Is it possible for someone to sketch a diagram of where to bond what when using a gennie?

-Dennis

[Jean-Pierre Coetzee]

Anything metal in a star ground to the ground rod.

That should cover your needs.

[randy amos]

I'm learning a bunch from this topic- Thanks for all the information.
 One question, though: When the job is over, how is the ground rod, all 8 feet pounded into potentially hard, compacted earth, removed? Is it considered an expendable and driven below grade and left in place? I don't know that I'd be comfortable doing that. I may be reading too much into the whole thing, and it is easily yanked out, but as I have never done it, I really don't know.

[g'bye, Dick Rees]

I'm learning a bunch from this topic- Thanks for all the information.
 One question, though: When the job is over, how is the ground rod, all 8 feet pounded into potentially hard, compacted earth, removed? Is it considered an expendable and driven below grade and left in place? I don't know that I'd be comfortable doing that. I may be reading too much into the whole thing, and it is easily yanked out, but as I have never done it, I really don't know.

Chances are that soil which will not allow you to remove the ground rod will not provide as effective a ground as one would wish.  You'll have a ground in name only. 

Often you must soak the soil around the rod with enough water to establish an effective ground, but even this is not easy to do.

[ProSoundWeb Community]