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Larry Campbell is an electrical contractor with 36 years of experience in residential and light commercial electrical wiring.
In your home"s wiring system, the grounding system is a critical safety feature. In the event of some kind of breakdown in the system, the grounding system provides a path of least resistance that ensures current will flow safety back to the earth itself. It thus reduces the chances that a short circuit can cause a fire or life-threatening shock. The final and most important part of a home"s grounding system consists of a metal ground rod driven deep into the earth, wiring thatconnects thisrod to a service panel or utility meter base grounding lug, and the connector clamp between the wiring and the rod.
This "earth ground"is a very important part of your electrical system to ensure electrical safety. According to the National Electrical Code, or NEC, a ground system should have a grounding resistance of 25 ohms or less. Achieving this may requiremore than one ground rod.
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Ground Rod Length
The grounding rod that connects the home grounding system into the earth is a long metal rod, usually copper bonded to steel, galvanized iron, or stainless steel.
Ground rods come in both 8-foot and 10-foot lengths, with 8-foot being the most common size used in residential installations. As a rule, ground rods must be a minimum of eight feet long and should not be cut down. In very dry ground, which provides more resistance than moist soil (meaning it does not accept electricity as readily), ground rods are sometimes stacked and joined with a special clamp so they can extend deeper into the earth.
Another option is to add a second ground rod. This is usually a better option, but the rods must be at least six feet apart, according to the NEC.
Note: Most local jurisdictions and local power companies require the 2-ground rod method to pass inspection. Some counties also allow or require a footing or foundation ground connection for new construction.
Whenever possible, ground rods should go into moist soil around your home. Usually, the area close to the foundation has enough moisture due to runoff water from downspouts.
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It is unwise and unsafe to install the shorter, 4-foot ground rods often sold for grounding things like TV antennas and other individual devices. These are not legal for grounding the home electrical service, and they can cause your grounding system to fail when it is needed most.