The first line of defense in protecting your equipment and appliances and ensuring their safe operation is the lowly, often forgotten, and inexpensive “Ground Rod.” This unassuming little metal rod is a key link in electrical safety and a very cost-effective insurance policy to protect your electrical equipment and appliances.
Household electrical systems are required by the National Electrical Code (NEC) to have a grounded system connected to earth ground via a ground rod. The Ground Rod is usually located very close to your main electrical service panel. The ground rod is often made of copper, or copper coated steel, approximately ½” in diameter or larger and 8–10 feet in length. It must be electrically tied to your main service panel to provide an approved ground connection.
Washington State requires the maximum resistance for a ground rod to be 25 ohms or less. If your ground rod impedance exceeds 25 ohms, additional steps must be taken to lower the impedance. Since 1990 it has been general practice to install two ground rods for safety.
To make a quick, visual check of your ground wire (often referred to as the grounding electrode conductor) that leads to your ground rod, go to your electric service meter. Most of these meters are installed on the outside wall of the house as near as possible to the main service panel inside the house. Toward the bottom of the wall there should be a wire coming out of the wall that is the link between the service ground connection and the ground rod. You should not see the ground rod, as it must be buried to be effective.
We have often seen ground rods not fully installed (12” to 18” or more still sticking up out of the ground), rods bent over, wire disconnected, and installed in very rocky and/or dry soil, etc. The resulting resistance in some of these cases is well in excess of 1,000 ohms. The lowest possible resistance is best and we have measured some as low as 15 ohms.
Unfortunately, we have no control over how well your electrical panel is grounded. If you do not provide proper grounding in accordance with the NEC, there is no way to mitigate electrical damage that may occur beyond your electrical panel. If you have concerns about your business or home grounding, contact a licensed electrical contractor.
Among the various situations that may occur on your electrical system, the most common are high voltage surges and damage or loss of one of the Service Conductors.
- High Voltage Surges (lightning or switching surges)—Failure to properly ground the electrical system can lead to the migration of elevated primary voltages to the premises wiring system, resulting in electric shock and/or fire due to failure of the 600 Volt insulation on the conductors.
- Damage or Loss of one of the Service Conductors—Failure to properly ground the electrical system can cause the voltage to earth during normal operation to elevate the premise wiring up to twice the normal voltage. This may be due to capacitive reactance in the circuitry, which may also stress the 600 Volt insulation on the conductors and lead to the premature failure of electrical equipment.
Another critical issue relative to sensitive electronic equipment is the proper installation and operation of Surge Protective Devices (SPD). The best surge protection equipment is much less effective without a properly installed and maintained grounding system. The SPD works by shunting damaging electrical surges away from your sensitive electronics to ground and they need the best possible ground to work properly.
It is therefore incumbent upon you to have and to maintain a NEC code-approved ground system as part of your electrical system.