This "earth ground" is a critical component of your electrical system for ensuring electrical safety. A ground system should have a grounding resistance of 25 ohms or less, according to the National Electrical Code. This may need the use of more than one ground rod. Ground rods are generally driven into the soil near large metal objects (such as an old gas meter) that will not be moving when electricity is flowing through the ground rod. The driver needs to be strong enough to pierce any dirt on its way into the ground.
The number of ground rods needed depends on several factors such as how far they must be driven into the soil and the type of soil they're being driven into. For example, if you are using zinc-coated steel ground rods, you will need about one per hundred feet along exterior property lines and within 20 feet of buildings. You would need more ground rods in areas where there are high levels of acidity in the soil due to nearby sources of sulfur dioxide or nitrogen oxides from local factories.
Grounding yourself with multiple ground rods helps prevent shocks from happening if water gets into the soil around one of the rods. The water can reach sufficient depth to cause problems for other rods farther away from the nearest utility line.
If you only have time to drive one ground rod per 100 feet, then you should do so along exterior property lines and within 20 feet of buildings.
However, as you correctly point out, most systems these days are PME. This implies that an earth rod is necessary for practically all installations to a garage, shed, or outbuilding. The presence of water is not going to cause any problems for this resistance if it's done properly. However, if there are any openings in the ground system, such as gaps between rocks or holes filled with soil, then these areas will be potential paths for current to flow through, which could cause damage to your property.
In conclusion, yes, a shed needs an earth rod.
Proper grounding is a critical component of the safety and protection of your business's and/or home's electrical system. As a result, the National Electrical Code (NEC) and local construction rules need one or more ground rods on your property. The ground rod(s) should be located at least 100 feet from any occupied building exterior or equipment enclosure and at least 20 feet from any elevated electrical service. The ground rod(s) should be driven into the soil with the upper end positioned at least 3 feet below the surface.
Grounding conductors must be connected to an earth conductor (e.g., metal piping located in the foundation or some other secure location). This connection should be made with wire connectors or mechanical fasteners that are designed for grounding circuits. A bonding jumper may also be required if there is a risk that two circuits might be bonded together by accident or otherwise. Bonding jumpers are thin wires that connect each conductor to each other, allowing current to flow through both paths even if only one conductor is damaged.
Ground faults occur when electrical energy from another source (such as a lightning strike) flows along a grounded circuit back to Earth. In order to protect people from these dangerous currents, modern buildings' electrical systems include protective devices called ground fault interruptors (GFIs). These devices check all the wiring within the building for voltage every time a power switch is turned off or a circuit is opened.
Almost all electricians and electrical inspectors are acquainted with the National Electrical Code requirement in Section 250-54, which requires a single-made electrode (e.g., ground rod) to have a resistance to ground of 25 ohms or less.
The reason for this requirement is twofold: First, it provides a good path back to the house or building structure if electricity goes to ground through someone's body; second, it reduces the risk of electrocution by allowing enough current to flow through the person's body to protect against serious injury or death caused by the electric shock.
The Code also requires that ground rods be deep enough to reach solid rock. The minimum depth required by the Code is 30 feet, but the best practice is for ground rods to be at least 60 feet deep.
Grounding electrodes should be placed close together to provide a low resistance path back to the house wiring. Too great a distance between ground points creates the possibility that enough resistance will develop between them to prevent current from flowing through a human body.
The resistance of an insulated copper wire depends on its diameter and length. For example, an ordinary home circuit conductor such as #12 wire has a resistance of about 1.5 ohms per foot. The resistance of a ground rod made of steel falls off more slowly than that of copper wire as the height increases.
The National Electrical Code requires that all household electrical systems have a grounded system linked to earth ground through a ground rod. These eight-foot-long rods are hammered into the earth. A ground wire should also be connected to the cold water supply. What is the significance of electrical grounding? Grounding is required on all households with plumbing, gas, or electricity to prevent people from being injured by electric currents. The ground wire connects one side of the house to the other in case someone falls into an open sink or toilet. It also protects family members who cannot get out of their beds if they were to receive a shock.
The code also requires that all outlets within 300 feet of a driveway or road must be protected by a GFCI (grounded conductor circuit interrupter). This means that if water gets into these outlets, it will be detected by the GFCI and shut off automatically. Outlets farther away from roads can be normal outlets without a GFCI if you meet certain requirements. For example, they don't have to be directly under a roof deck or in a conditioned basement.
GFCIs can be used instead of breakers in some cases. The code allows for this if there's no way to change out the breaker panel. In this situation, each outlet has its own breaker that stays on even if all the others are off. The cost of GFCIs can be higher than regular outlets but they can save lives.