Grounding Electrode (Ground Rod) Info and Install Suggestions
One thing that I always ask my clients about is the entire electrical chain feeding their audio system. How your audio system obtains AC power is essential, but I will only examine how your house is grounded to the Earth for this paper. It's not a fancy topic, and this will not be an in-depth information document. Still, it goes over the basics of obtaining a low-impedance path to Earth for the electrical service in your home. Ensuring a low impedance path to Earth here can sometimes yield a surprising jump in the performance of your audio system, provided the AC and ground path don't get compromised between the main service entrance and the audio system.
The primary importance of your electrical system's connection to Earth is dissipating hazardous and destructive electrical energy during a lightning storm. A low-impedance path to Earth also helps make the safety ground network in your home more efficient. It can also help to make a quieter and more stable electronic environment for high-end audio components. The better the Earth's ground system is, the more effective the electrical service will be in all these areas.
The Earth-ground relationship for a residential electrical system is traditionally achieved using a grounding electrode called the ground rod. Geeky technical detail here: A ground rod only becomes a grounding electrode when installed into the Earth. Until then, it's just a metal rod. The NEC (National Electrical Code) requires the grounding electrode to Earth impedance of 25 ohms or lower for residential electrical installations. Ideally, for a home with a high-end audio system, achieving 5 ohms or lower is highly desirable, and lower still is ideal. If the Earth-to-grounding electrode impedance is above 25 ohms, the ground rod may have deteriorated or may need to be longer for the current soil conditions around your home. The installation of the grounding electrode for your home was probably installed correctly, or it would not have passed the electrical inspection when the contractor built your home. That said, soil conditions may have changed since the initial installation, and reevaluating it would be a first step in determining what, if anything, needs to be done.
Suppose you've decided to have an electrician reevaluate the grounding electrode condition. In that case, it might be a good time to install a new ground rod with optimal performance in mind rather than just getting by to meet code requirements. And if you live in a home older than 20 years, a new rod would be a good idea regardless, as corrosion will have probably compromised a low impedance relationship to the Earth. NEC requires a minimum 8' length rod. If that 8' meets the NEC 25 ohm minimum, a longer rod that reaches deeper and closer to the water table will sometimes provide a lower impedance value. As there are various diameter rods available, keep in mind that the larger the diameter of the rod, the greater the contact area with the soil there will be, which will lead to a lower impedance value between it and the soil.
Since a ground rod is generally thought to last quite a while, a homeowner rarely (never...) thinks about how well it protects your home. However, with the electronic complexity found throughout modern homes, the grounding electrode should be a regular part of home maintenance. High salt or mineral levels in the soil can considerably speed up corrosion, depending on the metal the grounding electrode is made from. One can purchase a highly conductive pure copper ground rod, but copper is a pretty soft material. It can easily get misshapen when driving it into hard or rocky soil. A copper-bonded rod has negligibly less conductivity than copper, is much tougher, and is considerably less expensive than pure copper. For folks living in areas with high salt in the soil, there are also stainless steel grounding rods, which are very resistant to corrosion but have slightly higher resistance to Earth. An alternative to going deeper with a single ground rod is a second electrode located some distance from the first. . It will get bonded to the primary electrode and provide a greater surface area in contact with Earth. If you or your electrician determine that a second ground electrode is a good choice, NEC requires at least a 6' distance between the electrodes. However, there are some technical advantages to the electrode distance being equal to or greater than the rod lengths. 8' ground rod means the second electrode would be 8' or greater away, and doubled-up 8' rods 16' deep means the second electrode is 16' away from the initial electrode. Anyway, get that Earth to grounding electrode impedance as low as possible!
For you wildly ambitious people, an enhanced ground rod is another option to establish a very stable grounding electrode. An enhanced ground rod involves a copper tube filled with electrolytic salts and can be highly effective at establishing a long-term, very low impedance Earth to grounding electrode relationship. Enhanced ground rods require a significantly more sophisticated and costly installation process, not to mention the higher cost of the unit itself. But, if you live in an area where it is difficult to establish a low impedance result, or if you want to take grounding to the highest level of effectiveness, an enhanced ground rod may be just the height of grounding improvements. Remember that, unlike the common ground rod approach, an enhanced ground rod type system requires regular maintenance to keep it maximally effective.
Next, you must deliver that optimized low-impedance path for Earth ground to your home electrical system. When bonding the grounding electrode to the grounding electrode conductor (The wire going inside your house to the breaker box), there are, of course, options on how that is accomplished. Since we don't want to think about the house grounding all the time, I suggest having the conductor exothermically welded (using thermite) to the electrode rather than clamping it. The conductor is clamped onto the electrode with a bolt-on type connector with most homes, resulting in a potentially poor connection. This connection is often loose or somewhat compromised due to corrosion or oxidation. In that instance, there is a significantly higher impedance to Earth ground, regardless of the impedance between the electrode and Earth. Once it's welded, it stays there, and the bond impedance is extremely low. It's an old and common practice and should be relatively inexpensive.
There are kits on Amazon for you to do the DIY thing if you're cool with igniting thermite…but I'd let the electrician do it if I were you. Besides, suppose an open neutral leg is in the electrical system. In that case, the grounding electrode could carry hazardous current levels (read lethal)—yet another reason to let your electrician do this work for you. There are also very high compression bonding products and techniques that seem just as solid, long-lasting, and low resistance as thermite welding, but special tools and products are required to do this properly. This technique goes beyond getting the connection "really, really tight." There are pluses and minuses to both methods that you should ask your electrician about, but please consider one of these methods rather than clamping.
NEC dictates that the size of the grounding electrode conductor is no smaller than 6 gauge for copper wire. You can use aluminum wire here, but you introduce a dissimilar metal relationship to the grounding electrode, which causes galvanic corrosion between the two metals. A very low-impedance copper braid is probably the lowest-impedance path you can provide. However, check with your electrician for his recommendations and code requirements before plowing ahead yourself.
Once in the house, the electrode conductor is connected to the ground bus at the electrical service entrance for the house's electrical system. Once the electrical system enters the house, many things can foul up all the excellent work put into establishing everything discussed above. That is for another discussion.
There is a grounding topic I get questions about, and man, is it scary, not to mention disastrous for the system's performance! You do not want to connect the audio system safety ground to a dedicated or stand-alone second grounding electrode close to your audio system. Somehow there is misinformation out there that this provides the cleanest or quietest ground because nothing else in the house is connected to the audio system ground.
By doing this, the system's electrical system will not be grounded, nor will your house meet code. The safety ground of the electrical system MUST be connected to the neutral leg of the AC, which is the whole point of safety grounding. You can add a second grounding electrode near the audio system, but it must be connected back to the house grounding electrode to complete the circuit. But, this practice will probably do nothing but create potential ground issues (a ground loop) and add more noise. In other words, the audio system ground will have two paths back to the breaker box, connecting to the neutral leg, one directly through the house and the other to the secondary grounding electrode and then to the breaker box. Each ground path will have a different and UNEQUAL impedance value. The unequal resistance value between those two ground paths that connect to the same point means that current WILL flow to the safety ground. That's unwanted noise.
So don't do it.