Published by Pablo Diaz, P.Eng, Grounding Systems Technologies (GST), The Electricity Forum, Power Quality and Ground Articles.
What is Electrical Grounding?
Electrical Grounding is defined as the process of transferring the immediate discharge of electricity directly to the Earth with the help of a low-resistance wire.
Electrical grounding was invented as a safety system to help prevent people and equipment from accidentally coming in contact with electrical hazards. In a short circuit situation, electrical current wants to find the shortest distance to the earth that has the least possible resistance. A system has to be designed to allow a controlled path to ground that is safe. If not, then the uncontrolled path might be a person’s body or equipment. This can be injurious to people and damaging to equipment. Therefore, electrical grounding is accomplished by connecting the non-current-carrying part of electrical equipment or the neutral part of the supply system to the ground.
The National Electrical Code and Canadian Electrical Code provide rules to govern the proper installation of ground wires in an electrical system to avoid potentially dangerous electric shock accidents. The ground connection provides a path for electric current to flow, for instance from a circuit breaker or electrical box through an electrical connection to a cold water pipe that travels into the earth, and that assists the dissipation of energy into the actual ground.
These are the Top 10 Electrical Grounding questions people ask.
1. How do you Ground Electrical Boxes?
Plastic electrical boxes have their pluses and minuses. Because they are plastic, there is no need to attach a bonding conductor to it. Since it is made of a non-conductive material, switches and outlets cannot short out if they touch the side of the box. The only requirement is that the system is grounded.
When using plastic electrical boxes there is no need to attach a “Bonding Conductor”, because they are plastic, which means they are made with “No Conductive Materials.
You only need to bond those metallic boxes or “non-current carrying” metallic enclosures” which can carry electrical currents only during a “Ground Fault” or exposed to energized parts of the electrical system.
It is needed to attach a ground wire only to metallic boxes or boxes made of conductive plastics that conduct electrical current.
If the box is made from a material that does not conduct electricity, such as polyethylene plastic or glass, bonding or grounding is not necessary.
2. What is an electrical ground loop?
Improper grounding can create a lethal hazard. Correct grounding is essential for correct operation and safety of electrical equipment. Grounding can solve many problems, but it can also create new ones. One of the most common problems is called “ground loop”.
Generally, a ground loop connection is created when an electrical system is connected to ground at several points. When two or more pieces of equipment are connected to a common ground through different paths, a “ground loop occurs”. Currents flow through these multiple paths and develop voltages which can cause damage and noise in audio or video systems.
These problems occur because there is a conflict between safety and noise reduction.
To prevent ground loops, all signal grounds need to have a common point and when two grounding points can not be avoided, one side must isolate the signal and ground from the other.
3. What does “in open ground” mean in electrical terms?
An open ground is present when a three-prong receptacle does not have a “Bonding Conductor”.
These open grounds are common in houses built prior to the adoption of the 1962 electrical code. In these older homes the original wiring does not have the safety ground called the “bonding conductor”. In some instances, these houses have ungrounded outlets distinguished by their two-hole/slot rather than the tree holes slots.
The best fix available, rather than rewire the entire house is to utilize an ‘Ground Fault Circuit Interrupter” (GFCI), This device takes place of the standard outlet and replaces it with a special GFCI protected outlet. These are commonly used in the kitchen and bathrooms. They are known for their black and red buttons.
4. What happens if an electrical outlet is not grounded?
Ungrounded outlets increase the chance of: Electrical fire. Without the ground present, errors that occur with the outlet may cause arcing, sparking and electrical charge that can create fire
Grounding of electrical receptacles (which some laypeople refer to as outlets) is an important safety feature that has been required in new construction since 1962, as it minimizes the risk of electric shock and protects electrical equipment from damage.
An ungrounded outlet is it dangerous in that it dramatically increases personal and property risk and increase the chance of Electrical fire, health hazards (risk of shock) and property loss. It is important to note that it takes only 80 milliamps to cause death by electrocution.
5. What is a common ground electrically?
Electrical ground or earth is the reference point in an electrical circuit from which voltages are measured.
A neutral wire is the common current carrying wire in a multiwire electrical circuit. It is generally the wire to which all current carrying conductors are voltage referenced.
It may or may not be grounded, depending on the circuit requirements.
It is not the same as the ground wire in an electrical circuit, because a ground wire does not normally carry any current except in abnormal circumstances such as a ground fault.
But in a network set up (two hot’s sharing a neutral) the neutral is common. Terminology can cause great confusion in electrical work, be sure exactly which way the terms are being used or you could be in trouble. It is essential to use the terminology of the CEC.
6. What is the purpose of electrical grounding?
The term grounding is commonly used in the electrical industry to mean both “equipment grounding” and “system grounding”.
Equipment grounding means the connection of earth ground to non-current carrying conductive materials such as conduit, cable trays, junction boxes, enclosures and motor frames.
System grounding means the connection of earth ground to the neutral point of current carrying conductors such as the neutral point of a circuit, a transformer, rotating machinery, etc.
System grounding, or the intentional connection of a phase or neutral conductor to ground, is for the purpose of limiting the voltage to ground, facilitate the over-current device operation, stabilize the voltage-to-ground during normal operations and to drain leakage currents.
7. What does it mean by electrical grounding?
Electrical grounding is a direct connection to the earth.
Electrical grounding is important because it provides a reference voltage (called zero potential or ground potential) against which all other voltages in a system are established and measured. An effective electrical ground connection also minimizes the susceptibility of equipment to interference, reduces the risk of equipment damage due to lightning and eliminates electrostatic buildup that can damage system components.
When a point is connected to a good ground, that point tends to stay at a constant voltage, regardless of what happens elsewhere in the circuit or system. The earth, which forms the ultimate ground, has the ability to absorb or dissipate an unlimited amount of electrical charge.
8. How do I ground an electric fence?
An effective grounding system consists of three 6 to 8 foot grounding rods, ground rod clamps, and 20 KV insulated hook up wire.
The first grounding rod must be driven into the soil within 20 feet of the fence energizer. Additional grounding rods should be spaced 10 feet apart from the previous rod.
Using a ground rod clamp at each rod, connect the 20 KV insulated hook up wire to each rod in a linear fashion. Remember to strip the end of the wire so the metal is exposed when clamping it to the rod in order to establish a connection.
Once all three rods are connected one to another, the wire can be hooked up to the fence energizer. It must go to the ground terminal on the charger. Do not make the mistake of connecting it to the fence wire or fence terminal
9. How do I ground an electric motor?
Electrical motor windings are normally insulated from all mechanical parts of the motor. However, if the insulation system should fail, then the motor frame could become energized at line voltage. Any person contacting a grounded surface and the energized motor frame simultaneously could be severely injured or killed. Grounding the motor frame prevents this possibility.
The most common method is to use a grounding connector. This connector is placed into the motor’s frame. The other common method is to weld or braze a copper or steel ground pad to the motor frame. The ground should always bolt directly to the main part of the motor frame.
10. How to ground the main electrical panel?
The NEC/Canadian Electrical Code gives for ensuring electrical continuity at Main Electrical panel or service equipment. It requires bonding of all metallic electrical components and a Neutral-to-Ground connection
It requires Bonding jumpers to bond metal parts to the service neutral conductor. This requires a main bonding jumper because the service neutral conductor provides the effective ground-fault current path to the power supply.
It will require threaded fittings, to terminate metal raceways to metal enclosures by threaded hubs on enclosures. If using thread less fittings it must terminate metal raceways to metal enclosures if made tight.
It can also use. bonding-type locknuts, bushings, wedges, or bushings with bonding jumpers.
When a metal raceway containing service conductors terminates to an enclosure without a ringed knockout, you can use a bonding-type locknut. Bonding one end of a service raceway to the service neutral provides the low-impedance fault current path to the source.