Installing an AC Grounding System, Need Advice

The feed from your existing service that will feed the 7.5 kva xfmr will be 2hots, 230v,+ 1 equipment grounding conductor. The equipment grounding conductor will bond, connect, to the case of the xfmr. This ground is for the xfmr only.
Think of this ground as a safety ground.

When you install a transformer of the size you are using you are creating basically a new service. That means the 120 volt secondary side of the xfmr must follow certain safety guidelines to meet the NEC and your local city codes. That is why you need to connect one of the 120 volt leads of the secondary of the xfmr to the neutral bar in the new electrical panel that will be installed. This wire will become the "grounded conductor", the neutral. From this neutral bar a #6awg cu ground wire will run to the main incoming water line ahead of the water meter. This wire is called the "grounding electrode conductor". The wire attaches to the water pipe with an approved water pipe ground clamp. The water pipe is now called the "grounding electrode". This is the primary "grounding electrode" and "grounding electrode conductor" I spoke of in my earlier post. The connection at the main water line is the common ground point that ties your new 120v service to your existing house service.They will both be on the same ground plane. Now back to the neutral bar in the new panel. The electrician will install a supplied bonding screw through the neutral bar into the panel enclosure. Now for the secondary grounding electrode conductor that will go outside to the second "ground electrode" you choose to use. This second ground also connects to the neutral bar in your new panel.The new panel will have two earth ground system connections. Primary,water line ground electrode, and secondary, outside new earth ground electrode. The neutral bar is a Star grounding point now. By the way in your area your water line is probably down 4 to 5 feet deep because of frost. Buried in moist clay the distance, length, from the house to the main trunk connection and beyond.
Back to that neutral bar in the new panel. This bar is where all the new branch circuit neutral wires and equipment grounding wires will terminate...Nec says the neutral shall be bonded to ground at the first point of attachment or disconnecting means and at no point there after. That is why sub panels have seperate equipment ground bars. This is not a sub panel. In this new panel the neutral wires and ground wires share the same connection bar, called the neutral bar. NEC also says the max resistance between the neutral, grouned conductor, and the equipment grounding conductor measured at the receptacle shall not exceed 3 ohms. Also If you can keep the new panel fairly close to the new branch circuit receptacles thats also agood thing.

I have tried to do a better job of explaining things. This is the simple part. Putting it all together in a neat and workman like manner is the tough part. Local codes can vary. Your electrician should know the code of your area.

Cincy: You really can't do a free, engineering project via an audio Forum. That's a bit much to expect, both financially and even more importantly, from a liability standpoint. You are very bright, curious, and well spoken, but, respectfully, and I'll buy the first beer - y'all are drifting into a real project. And, respectfully, if we don't know that ground rods come in 10 ft lengths, and that driving one takes a specialized tool, and is the ultimate in apprentice physical labor, and that there are a ton of NEC requirements to be met, well...

Saying that you may want to consider engaging a freelance (not an engineering company) registered electrical engineer to prepare several drawings on what you wish to do. You can verbalize your electrican through it, but, that is always poor practice. That includes an as-build of your entire home system. Expensive, but hand waving a Journeyman electrican will burn up a stupid amount of hours; and here in N. CA, the billing rate will be about $80/hour.

Not a shareholder, employee, sales rep of any mentioned product. The XIT system is a large, hollow ground rod packed w/ trick material. It is vented at the top to absorb ambient humidity, thusly maintaing a very low impedance with the contacting soil throughout the year despite weather conditions. It is used by Honeywell for their DCS (Distributed Control Systems) in their localized Remote Instrument Enclosures handling plant control of digital inputs/outputs and analog signals in the milliamp level. It is installed in at least one Chevron refinery in California.

It also is, possibly, stupid overkill for a residential app., but in this day and age when 6loons is reviewing new-car priced transports/DAC's, I'm lost...

If your curent system is in good condition, and has a measured reasonable impedance, I wouldn't loose sleep on this...

Shasta, about a month ago, I hired a registered electrical engineer to develop drawings for the modifications to my residential electrical system. What I have been doing in this forum is educating myself so that I can raise the right topics with - and ask the right questions of - my electrical engineer and my electrician.

The service drawings for my system do not contain any detailed specifications for the grounding of the new circuit panel. Without the aid of this forum, I would not have known that there was any alternative to simply grounding the new panel back to the incoming water line that currently serves as the grounding electride for my electric system. And, without any discussion of the topic with my electrician, I am sure he would have opted for this single ground without any discussion and without me being aware of any alternative for a secondary ground. The education Jea48 has provided me regarding the option of installing a secondary outside new earth ground electrode allows me to have an intelligent conversation with my electric professionals that I could not otherwise have even initiated.

Jea48, thanks very much for all the information you have shared. It is very helpful to me and will significantly enhance my ability to communicate with my electrical engineer and electrician.

I'd check out www.equitech.com. They're the people into balanced power; however, they also have different articles that can be downloaded via computer. One of these articles is "setting up an a/c ground." I used one 10' 5/8" copper ground rod. If you use two, they need to be separated by at least 8'. As for putting the ground rod into the ground... Use water. Slowly dribble it into the hole that the rod is making, as you plunge it up and down. The pressure of the rod tip--(like a high heel shoe-pressure per square inch, ouch!), and the water at the hole's developing surface will cut through the dirt in no time. Be careful with that project. I've read multiple grounds can be dangerous. Hope all this helps. Good Listening!

Water method, better not let an electrical inspector catch you do it. The correct way is to drive the rod into the earth. Undisturbed earth. When using multiple rods they must be connected all together with an aproved wire to rod connecting means. Local codes very all over the place on the connecting means to be used.