Power generator and mains grounding?

The short answer is you should tie all grounding electrodes on a property together with 6ga copper conductors. We don't have enough information yet to answer how you are grounding the neutral but if everythig is tied together you will be using the main bonding jumper in the service disconnect and that is sufficient. You only want one place where the white and trhe ground get connected but you can have the ground electrrode system itself connected as many places as you like. Pick a single source and a single ground connection for all of your audio equipment to minimize the hum problems. You still may end up with isolation transformers on the audio side connections.

I do this stuff all the time. There are a couple of solutions you work on, depending on the money/time/personalities involved. First option: Go with 100% generator power or 100% shore power for everything. Second option: ( which is what you already did) Put all the audio and video stuff on one and only one source of power. Third option, have the audio and video folks put isolation transformers on all their signal lines that connect from the generator power system to the utility power system. Fourth option: Run a heavy gauge conductor from the ground stake at the generator and connect it to the utility power ground, making it all one ground system. You need to work with your local electrical inspector, as what you want to do has some non-obvious hazards, and they are not normal electrical practice. You don't mention where you are located, as the rules vary from country to country. If you are in the US, I'll come out for a suitable day rate and expenses to consult on the issues. *grins*

--Dale

If the generator ground and the building ground are of different enough potential to cause you voltage problems in the ground loops then just running 6ga conductors between them may not fix your problem either. It would depend upon how long of a run you would have to make to attach the two grounds together. You might just be better off running a 6ga conductor to the building ground and using that as your grounding point for everything.

tim

OP, here.

Since the 2 supplies are in all other respects separate, shouldn't the neutral be tied to the ground for each supply even though the grounds are (or will soon be) common?

Another question: Where should the grounds be connected? The generator is about 75 yards from the building (permanent structure) with the tents between the two. Simplest is to run a conductor from the generator's ground conductor where it reaches the tent (at the load), to the service entrance of the building.

Also, should the generator's ground -- connected to the ground rod at the generator -- be disconnected in lieu of the ground rod at the utility service entrance? Or is it "the more, the merrier" when it comes to ground rods? (The tent skeleton has its own ground rod, too, BTW, not connected to any electrical ground.)

In Maryland, USA, near Bethesda.

Thanks much,

Thus spake DaveC:

To clarify: Should the generator's ground... be disconnected *from the ground rod at the generator*...?

Just to point out, If this was a UK installation, the power supply company would have some major issues with the grounds/earths & neutrals being tied together.

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For an event of this magnitude and in the interests of public safety you should have an electrician doing the work for you or at least supervising and planning the work you are doing.

Don't even think of doing this without a skilled and experienced electrician. Don't be surprised if he contacts the utility for further assistance.