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Installing an AC Grounding System, Need Advice

Later this week, my electician will begin work on my electric project, which will involve the installation of a 7.5kVA isolation transformer that will be fed from a separate meter tap. The isolation transformer will be installed in front of a new dedicated circuit panel that will house the dedicated circuits that will feed my listening room. All the dedicated circuits will be fed from the same side of the bar in the new panel in order to maintain consistent phase.

As Sean has advised in a separate thread, I know it is important that I check - and upgrade as necessary - the ground for my AC system. (My house was built in the late 1950s, and, from the looks of things, not much has been done since that time to upgrade the electric service. So I am nearly certain that I will find the grounding system leaves much to be desired.) I also know from discussion in various other threads that it is important for the entire electrical system in my house to share a common ground. So I expect that I will need to upgrade the grounding system into my main circuit panel and then tie the isolation transformer and the new dedicated panel back to that same grounding system.

The work on my house is being performed by a qualified electrician, but, as I have noted in other threads, I would like advice on the audiophile details that can make a difference in the sound (in this case, the noise floor) of my system. Perhaps I should also mention that my plan involves installing a separate dedicated circuit for each of my seven components. Given that this sort of a set-up is more prone to ground loops, I am interested in advice regarding how to avoid them with this set-up.

With that as background, would any of the resident experts be willing to share with me the details of how to install a high quality grounding system for my AC power? I would appreciate as much detail as possible regarding the materials to use as well as installation advice.

I have read some advice in other threads recommending two separate copper grounding rods driven into the ground relatively close to each other with a weather-proofed connection between the two rods that is, in turn connected to the electrical system. I have also seen some advice that I believe involves wiring one of these connected ground rods to the main house circuit panel and the other connected ground rod to the audio portion of the system (i.e., in my case, the isolation transformer and the new dedicated circuit panel). Please let me know if this is headed in the right direction and, if so, please help me to fill in some details (dimensions of the copper, advice on how to drive it into the ground without mangling it, distance between the redundant rods, any other details you see fit).

As always, thanks for your help and patience.
cincy_bob

Showing 2 responses by shasta

shasta
155 posts
 
Sigh, stand back for a rush of unsafe, uniformed advice; starting off with 2 separate ground rods. There's only one way to do a grounding system (is this a house under construction?) and that's at least NEC minimum, and even that can be improved on. Any cock-eyed deviations from that will induce laughter from your electrician and scowls from the inspector.

Do a real, Code-defined, isolated ground install for *each receptacle. Any Journeyman electrician should understand this.

Install a Lyncole XIT ground rod system. Watch your electrical contractor's eyes bug out as they start to call you Sir and Mister. If this is an existing house, leave the current rod in place, and use the XIT as an adjunct. Scrub, clean, and retighten all exsisting connections on the existing rod. BTW, you'll never drive a rod yourself...

If an exist. house, call the utility and get a 4 hour disconnect. Clean and retorque the incoming lines at the service panel. Then, clean and retorque everything on the load side of the main breaker.

*I* would have done metallic conduit; but the twisted wiring is certainly a nice feature. That's why they make vanilla and chocolate...

Obssesive was actually a left-hand complement-- *grin*. When I bought my condo several years ago, I replaced all switches and receptacles w/ Leviton 20A Spec grade devices. Wire ends were cleaned, everything backwired clamped, and I purchased an Armstrong torquing screwdriver for finalizing the connections; required per NEC 110.3(b).

Recap: Torque all connections, new or old. Isolated ground for every receptacle. XIT ground rod. Have the impedance checked on the grounding electrode conductor, and shoot for *way under the NEC 25 ohms number; which the XIT should deliver.

Strike the set, it's a wrap.
shasta
155 posts
 
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...
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