According to the National Electrical Code, or NEC, a ground system should have a grounding resistance of 25 ohms or less. Achieving this may require more than one ground rod.
Ground rods, also known as grounding electrodes, are used to connect the grounding system of electrical systems to earth ground. Ground rods can be made with many different materials, but copper is the most common material used for residential installations.
Ground rods are very good conductors of electricity and allow any dangerous electricity to flow to ground, taking the danger away from you and the electrical panel. 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 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. 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.
The ground wire, often referred to as the grounding electrode conductor , is the link between the ground rod and the service ground connection. Ground wires for residences typically are made of copper and are 6 6 AWG or larger.
Grounding clamps are used to connect the grounding electrode conductor to the ground rod. Center for Construction Research and Training. A visual check of grounding can be done by inspecting the wire that connects the electrical panel near the meter to the ground rod. Below the surface, the wire is connected to one or more ground rods. The tops of the ground rods are typically below the surface and may not be easy to inspect.
However, sometimes ground rods extend a few inches above the surface, making it easy to inspect the connection. In some cases, problems with ground rods are easy to see. Rods that are not fully installed may extend a foot or more above the surface of the soil.
This reduces the effectiveness of the ground. Ground rods that are bent over, have disconnected wires or are severely corroded must be replaced. Ground rods that are installed in rocky or dry soil should be checked to make sure they still have a low resistance. If soil conditions change due to drainage or other factors that affect soil moisture, a ground rod that was acceptable at the time of installation may no longer meet approved requirements.
It will also probably not improve what you have substantially. Reply to DanG. Thomas Horne Contact options for registered users. Terry The quality of your Grounding Electrode System may not be the culprit here. If all of your wire carried utilities are not bonded to the same Grounding Electrode System the differences in potential between the separate utilities equalizes through the commonly connected devices such as Modems, fax machines, computers, answering machines, and so fourth.
The first task is to assure that all of the Grounding Electrode Conductors for the different systems terminate to the same Grounding Electrode System. If separate Grounding systems exist then you must bond them all together into a single system. Meaning no offense I must warn you that the knowledge and skills to perform equi-potential bonding is beyond the skill set of most do it yourself folks. Terry wrote: Show Quoted Text. Reply to Thomas Horne. Yes, I have read your helpful suggestions in the past.
This is one of the reasons I am trying to locate the point my panel is grounded. I have not been able to find a place where the copper pipe in the basement has been grounded. This is where the CATV and phone are bonded. As near as I can tell, the copper doesn't even come in contact with earth. It is true that it might not be the culprit, but for now, it is the only remedy I have.
I think I have dug as far as a shovel will go and no sign of the ground rod. I was hoping someone familiar with building footing construction might have an explanation of where I am with the shovel. If the house is a rebar type grounding system, then it is possible that the water pipe has been grounded at the point the copper pipe enters the laundry, but without cutting holes in sheet rock I can't verify this. I do have an alternative route for fishing an interior wall, if I have to, but it really would be the best place if I could just attach another ground clamp to the existing ground rod.
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