The NEC requires all driven rods to be at least eight feet into the soil, with a minimum spacing of six feet between rods if numerous linked rods are used. The actual distance that a rod extends into the ground will depend on how deep it is placed; for example, a rod four inches in diameter should be placed no less than two feet into the soil and should be sunk as deep as possible without binding or sticking. Linked sets of three or more grounded conductors must be at least six feet apart.
If you have several grounded conductors near each other, you should place them at least eight feet apart from one another. If you cut any conductor, the entire set becomes ungrounded, so care must be taken not to put yourself at risk by installing your equipment too close to other objects that could serve as alternate paths for current.
The actual depth that a grounding rod sinks into the soil depends on many factors such as soil type and condition, but generally speaking, you want to place it at a depth equal to about one-half its diameter. For example, if you were to sink a rod four inches into the soil, it would be best if it were able to reach a depth of two feet before beginning to bind or stick. You should also remember that ground rods work best when they're not touching anything else in the ground.
A ground rod must be at least 8 feet long, according to the NEC and UL. This standard was clearly developed by engineers who had never driven a ground rod or noted that most humans are not 8 feet tall. Longer rods are riskier to install and bow more when pushed. The minimum length provides enough reach so that you don't need to drive each one all the way down into hard soil.
The requirement is based on math, because engineers love math. The current flowing through a human body is about 0.5 amperes. If a rod is not at least 8 feet long, then it cannot safely conduct this current. An electric shock could happen if too much current flows through someone.
The reason for this requirement is that the longer the path between your house and any electrical source of danger (such as a power line), the lower the resistance will be. Lower resistance means more current will flow when you touch two different points of a conductor, such as a metal rod. The current will want to go from high resistance to low resistance, so it will try to follow the path of least resistance. This means it might not always pass directly through the middle of the rod, which could cause it to get stuck or bent.
If you shorten the rod, then there's less distance for current to travel, so there would be less resistance and less chance of an accident happening.
The ground rod is located a long distance away from the main electrical panel. It's conceivable that three wires will be needed. Ground rods must be at least 6 feet apart and linked by a buried jumper wire in regions with significant electrical resistance in the soil. The grounded conductor should be connected to the frame or body of any vehicle using a black, red, and white wire. This provides additional protection for drivers if a wire becomes damaged.
Grounding equipment is used in industrial facilities, commercial buildings, and residential homes to prevent electrical shocks and fires. Workers use electric tools when working on the power line. These tools give off small electric currents which would otherwise go unnoticed. A ground system allows these currents to be diverted into the earth instead, thereby preventing harm to people and property.
Electrical wiring within a building or home is called mains wiring. This wiring brings electricity into your house from the street pole or transformer and passes it along through walls, floors, and ceilings to all the various outlets in your home. It can be easy to forget that this main wiring needs to be protected too! That's where the ground rod comes in. The ground rod is first connected to the frame or body of any vehicle using a black, red, and white wire.
Then, the ground rod is placed near the main electrical panel, usually inside the wall.
No Unless you can demonstrate that one rod will turn less than 25 ohms of resistance, you must use two rods at least six feet apart. That is all there is to it. Run as many extras as you like, but two rods are required unless one rod has fewer than 25 ohms. Of course, if you can show that one rod will not turn more than 15 or 20 ohms, then three or four might be necessary.
The answer is yes, a house can have multiple ground rods. However, only one may be connected to the electrical panel at any given time. The other ground rods should be disconnected and tied off to prevent current from flowing through them.
Tying off ground wires is very important. If they are not tied off, electricity could flow through them which could cause damage to your home or injure someone. Grounding equipment must be treated with respect and care, and should never be placed in a location where it could be damaged by water or exposed to sunlight. A professional electrician should tie off ground wires for you.
If you're not sure whether or not you need additional ground rods, contact an electrician first before digging any holes.
Assume you are driving the first ground rod in a system. 250.56 of the 2005 NEC requires you to drive a second rod if it has a ground resistance of 25 ohms or greater. Because their effective resistance zones overlap, ground rods positioned fewer than two rod lengths apart will interfere with each other (Fig. 4-8).
The purpose of the second ground rod is to provide an additional path for current if the first one breaks or becomes damaged. The new ground rod will then take its place so that electricity can still be safely contained within the foundation.
Current flows through any open circuit or broken conductor to the next intact element of the circuit. If the first ground rod fails, current will continue to flow through the second rod, which will now be the only ground. You must ensure that none of these rods become exposed during an earthquake because even slight movement could break a wire connection, allowing current to escape through your body.
People often ask me about the best time to put in a new ground rod. The short answer is that there is no "best" time; it depends on where you live and how large your home is. In general, you should try to have at least one ground rod in place before you start work on your foundation. This will help prevent electrical problems after you move into your home.
If you're not sure when to put in your first ground rod, call an electrician.