Grounding Electrode (Ground Rod) Info and Install Suggestions
One thing that I always ask my clients about is the fundamental electrical system feeding their audio system. How your audio system obtains AC power is a pretty big and important topic to talk about, but for this section, we are just going to be examining how your house is grounded to the Earth. It’s not a very fancy topic and this will not be an in-depth information discussion, but it goes over the basics in obtaining a low resistance ground path to ground for the electrical service in your home. Ensuring a low impedance earth ground here can yield a surprising jump in the performance of your audio system, provided the AC and ground don’t get compromised between the main service entrance and the audio system.
Very simply put, the importance of ground is to prevent injury or death in the event an electrical appliance malfunctions or misuse, dissipating destructive electrical energy during a lightning storm, and in the case of high end audio components, helping to make for a quieter and more stable electrical environment. The better executed the ground system is, the more effective the electrical service will be in all these areas.
The ground for a residential electrical system is traditionally achieved using a grounding electrode, commonly referred to as the ground rod. Geeky technical detail here: A ground rod only becomes a grounding electrode when it is installed into the Earth. Until then, it’s just a metal rod. The NEC (National Electrical Code) requires the grounding electrode to earth resistance to be 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 ground resistance to the grounding electrode is above 25 ohms, either the grounding rod is not long enough to achieve this value with the current soil conditions, it is very corroded and too resistive to the soil, or a second grounding electrode may be required. The grounding electrode at your home was probably initially installed correctly or it would not have passed the electrical inspection when the home was built. That said, soil conditions may have changed since the initial installation and it may need to be re-evaluated to achieve the required low resistance result.
If the electrician is going to re-evaluate the grounding electrode set-up, it might be a good time to install a new one 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 electrode would be a good idea anyway as corrosion on the rod will have probably compromised a low resistance related to the Earth. NEC requires a minimum 8’ length rod but depending on the soil and water table in your area, multiple rods connected may yield better results. There are various diameter rods available, just keep in mind that the larger the diameter, the greater the contact area with the soil, which may lead to a lower resistance value between it and the soil. They typically last quite a while, but high salt or mineral levels in the soil can speed up the corrosion process quite a bit, depending on the material from which it is made. One can purchase a highly conductive pure copper ground rod, but copper is a pretty soft material and can easily get misshapen when attempting to drive it into the 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. If it is determined that a second ground electrode is required, NEC requires at least 6’ distance between the electrodes, but there are some technical advantages to making the electrode distance equal or greater than the rod lengths. 8’ ground rod means the second electrode is 8’away and doubled up 8’ rods that are 16’ deep means the second electrode is 16’ away for the initial electrode. Anyway, get that earth ground resistance as low as you can!
Next, you have to deliver that great low resistance path to 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 probably don’t want to be thinking about the house grounding all the time, I would suggest having the conductor exothermically welded (using thermite) to the electrode rather than clamping it. With most homes, the conductor is clamped onto the electrode with a bolt-on type connector, resulting in a fairly poor connection. In many instances, I’ll bet this connection is loose or is at least somewhat compromised due to corrosion or oxidation. If that’s the case, there is significantly higher resistance to Earth ground, which means you are not cannot fully accessing that low resistance to earth ground at the grounding electrode. Once it’s welded, it’s there to stay and the resistance of the bond is extremely low. It’s an old and common practice and should not be expensive to have done. There are kits on Amazon for you to DIY the thing if you’re cool with igniting thermite…but I’d let the electrician do it if I were you. Besides, if there is an open neutral leg somewhere in the electrical system, the grounding electrode COULD be carrying very dangerous 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 to be just as solid, long-lasting, and low resistance as thermite welding, but special tools and products are required to do this properly. This technique is well 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 the that size of the grounding electrode conductor is no smaller than 6 gauge for copper wire. You can use aluminum wire here, but then you just introduce a dissimilar metal relationship to the grounding electrode, which causes galvanic corrosion between the two metals. Copper is lower in resistance so just go with that.
Once in the house, the electrode grounding conductor is connected to the ground bus at the electrical service entrance for the house electrical system. Here,
There is a grounding topic I get questions about and man is it a scary one, not to mention disastrous for the performance of the system! One thing you do not want to do is connect the audio system safety ground to a dedicated second grounding electrode that is located close to your audio system while disconnecting the house ground from the system. Somehow there is info out there that this provides the cleanest ground because nothing else in the house is connected to the 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 absolutely MUST be connected back to the house grounding electrode to complete the circuit. But, this practice will probably do nothing but create potential to ground issues (a ground loop) and add more noise. What that means is, the audio system ground will have two paths back to the breaker box where it connects to the neutral leg, one directly through the house and the other to the secondary grounding electrode and then from there to the breaker box. Each ground path will have a separate and UNEQUAL resistance value. The unequal resistance value between those two wires that connect to the same points means that current WILL flow to the safety ground. That’s unwanted noise. So don’t do it!