How Many First-Level Subdivisions Exist in Section 250.122? An Analysis of Education Requirements

How many First-Level Subdivisions exist in Section 250.122?

Section 250.122 of the National Electrical Code (NEC) is a fundamental requirement that must be followed to ensure that we have safe electrical installations. This section outlines the requirements for grounding and bonding of electrical systems and services to protect people and property from electrical hazards.

Electrical contractors and installers must adhere to the NEC to keep people safe and ensure electrical installations are performed correctly. However, understanding the NEC requirements can be challenging. Section 250.122 contains several subdivisions, and this article will explore how many first-level subdivisions exist in this section.

The primary objective of Section 250.122 is to ensure that grounding and bonding of electrical systems are effective and efficient and provide adequate protection against electric shock and fire hazards.

The first-level subdivisions of this section are divided into three sub-sections:

250.122(A): Grounding Electrode System and Grounding Electrode Conductor

This first-level subdivision covers the requirement for grounding electrode systems and grounding electrode conductors. This section mandates that connection to a grounding electrode must be made at the service equipment, at each building disconnect, and at each separate structure.

The grounding electrode conductor must follow a specific minimum size, and the grounding electrode system must be installed in a manner that provides a low impedance to the earth and is corrosion-resistant.

The intent of this first-level subdivision is to ensure that the grounding system of the electrical installation is adequate to safeguard people and property from electrical hazards and protect the electrical system from damage caused by lightning surges and other electrical disturbances.

250.122(B): Equipment Grounding Conductors (EGCs)

This subdivision outlines additional protection provided by equipment grounding conductors (EGCs) to minimize shock and fire hazards. EGCs connect the non-current-carrying metal parts of equipment to a reliable, low impedance path to the power supply source.

This provides a low-impedance path to the ground to clear a fault and ensure that the electrical system’s overcurrent protection operates as expected. The size of the EGC is dependent on the circuit breaker or fuse size and must comply with the NEC provision.

Ensuring the equipment grounding conductor is satisfactory reduces the risk of electric shock and maintains the best protection of electrical systems and equipment.

250.122(C): Bonding of Services and Electrodes

The last first-level subdivision, Section 250.122(C), describes the requirements for bonding of services and electrodes. The main concept of this section is to ensure all metal parts that could carry a current are bonded to minimize potential differences and reduce the risk of electric shock and fire.

The section mandates that all conductive materials entering a building must be bonded, including service raceways, enclosures, grounding conductor and electrodes, and any other conductive element. All metal parts of services installed must be bonded together, with sufficient wire gauge to maintain the low-impedance ground path.

Proper bonding of services and electrodes helps minimize potential differences between conductive metal components. With this action, there is less risk of damage to electrical devices, electric shock, or fire.

Conclusion

Section 250.122 of the National Electrical Code (NEC) mandates the requirements for grounding and bonding of electrical systems. The first-level subdivisions of this section are contained in three sub-sections: Grounding Electrode System and Grounding Electrode Conductor, Equipment Grounding Conductors (EGCs), and Bonding of Services and Electrodes.

The objective of Section 250.122 is to provide safety and security to people and property from electrical hazards. Therefore, electrical contractors and installers must ensure that every electrical installation they do complies with the NEC.

Overall, it is essential to know and understand the NEC requirements and the significance of these requirements to ensure safe electrical installations and the protection of people and property.

Overview of Section 250.122

Section 250.122 is an essential part of the National Electric Code (NEC) that provides grounding requirements for electrical systems and equipment. The section outlines the minimum grounding requirements that must be met to ensure electrical safety in buildings. This section’s primary objective is to prevent electrical shock and limit the damage caused by electrical faults. It aims to protect personnel and equipment from the hazards of electric shock and fire caused by faulty electrical systems.

First-level subdivisions in Section 250.122

Section 250.122 has two main parts, which are the (A) and (B) subsections. Each of these subsections contains specific requirements that must be met to ensure proper grounding.

Subsection (A)

Subsection (A) contains requirements applicable to all electrical installations, including service, feeder, and branch-circuit grounding. The subsection emphasizes that grounding must be done under normal conditions of use and fault conditions. It also outlines the provisions for grounding equipment, raceways, and enclosures to ensure the continuous path for fault current.

The subsection provides detailed requirements for grounding of service equipment such as metal parts of water piping systems, building structural steel, and concrete-encased electrodes. It also outlines the grounding electrode requirements for separate buildings and structures that are supplied by a feeder or branch circuit.

Subsection (B)

Subsection (B) contains specific requirements for grounding systems that supply sensitive electronic equipment. The subsection aims to protect electronic equipment from the effects of lightning, electrostatic discharge (ESD), and electromagnetic interference (EMI).

The subsection outlines the provisions for grounding and bonding of sensitive electronic equipment, power distribution units, and surge protective devices. It also provides requirements for ground-fault protection of equipment (GFPE), which is essential for protecting equipment from ground fault current and preventing damage to the equipment.

In conclusion, Section 250.122 is vital in ensuring safe and effective electrical grounding in buildings. It provides specific requirements for grounding electrical systems and equipment, ensuring continuity and safety under normal and fault conditions. The two subsections, (A) and (B), outline the minimum grounding requirements that must be met to ensure electrical safety in buildings. Compliance with this section is crucial in preventing electrical hazards, injuries, and damage to electrical equipment.

Different Types of Grounding

Grounding is done to ensure the safety of people and equipment. It helps to prevent electrical shocks and fires. Within section 250.122, there exist three different types of grounding. These include:

Equipment Grounding

Equipment grounding is the most basic and common type of grounding for electrical systems. It involves connecting all electrical equipment and appliances to a grounding conductor. The purpose is to provide a low-resistance path for electrical faults or excess electrical current to flow to the ground. This method helps to prevent injuries, damage to equipment and appliances, and even loss of life that can result from electrical shock or fire caused by high voltages.

System Grounding

System grounding involves connecting a conductor to the earth that is connected to the electrical system. There are two types of system grounding: solid and impedance grounding. Solid grounding involves connecting the system to the soil via a conductor with almost zero impedance. Impedance grounding involves connecting a resistor in series with the ground conductor to limit the flow of fault current.

Effective Grounding

Effective grounding is the combination of equipment and system grounding. It ensures that there is a proper grounding system installed in a facility. This type of grounding ensures that there is a low-impedance ground path for all currents, including electrical faults. It is achieved through the installation of ground rods or conductors that are connected to earth. An effective grounding system also prevents interference and power quality issues that can occur in electronic systems.

Understanding the different types of grounding is important when installing electrical systems. It helps to ensure that the system is safe and functions properly. It is essential to follow the requirements set out in section 250.122 to ensure compliance with safety standards.

Introduction

Section 250.122 is a critical component of the National Electrical Code (NEC) that sets the standards for grounding and bonding of electric equipment. This section outlines the requirements that must be met for grounding conductors, grounding electrode conductors, and bonding jumpers, among others. The section is subdivided, with each subdivision providing detailed information on specific subjects.

The Five Subdivisions

There are five first-level subdivisions under Section 250.122, with each one providing detailed information on specific aspects of the grounding and bonding requirements. These five subdivisions include:

250.122(A) Scope

Subdivision 250.122(A) defines the scope of the section, outlining the requirements that apply to all grounded systems, conductors, and equipment. It provides information on grounding for alternating-current (AC) and direct-current (DC) systems, as well as grounding for separately derived systems, such as generators and transformers.

250.122(B) General Requirements

Subdivision 250.122(B) outlines the general requirements for grounding and bonding, including information on bonding services and the grounding requirements of conductive materials and enclosures containing electrical conductors. It also provides detailed information on grounding of equipment, raceways, fittings, and supplementary grounding electrodes.

250.122(C) Methods of Grounding and Bonding Conductor Connection to Electrodes

Subdivision 250.122(C) provides detailed information on the connection of grounding and bonding conductors to electrodes, including the use of clamps, exothermic welds, mechanical connectors, and other bonding methods. It also outlines the requirements for grounding electrode conductors and the bonding of grounding electrode systems.

250.122(D) Connection of Grounding and Bonding Equipment

Subdivision 250.122(D) provides detailed information on the connection of grounding and bonding equipment, including the use of grounding electrodes, ground fault circuit interrupters, and bonded neutral systems. It also provides information on the requirements for grounding of equipment, raceways, and enclosures.

250.122(E) Equipment Grounding Conductors

Subdivision 250.122(E) provides detailed information on equipment grounding conductors, including their size, ampacity, and installation requirements. It also outlines the requirements for the connection of equipment grounding conductors to enclosures, raceways, and equipment grounding terminals.

Conclusion

Section 250.122 is a critical component of the NEC, outlining the requirements for grounding and bonding of electrical systems and equipment. The five first-level subdivisions under Section 250.122 provide detailed information on specific aspects of grounding and bonding requirements, ranging from general requirements to equipment grounding conductors. Understanding these requirements is critical for ensuring safe and effective electrical installations.

Grounded Systems

Grounded systems refer to how electrical systems can and should be grounded to prevent electrical shock. This includes electrical power systems as well as communication circuits. The goal of grounding is to provide a path of low impedance for electrical current to follow if a fault or surge occurs. In other words, the goal is to prevent electrical shock by creating a path of least resistance for electrical current to follow in the case of a fault or surge.

Grounding Electrode System and Grounding Electrode Conductor

The grounding electrode system refers to several different pieces of equipment that work together to create a path of least resistance for electrical current to follow to the earth when a fault or surge occurs. The grounding electrode system includes ground rods, bridge bonds, grounding plates, and other types of equipment. The grounding electrode conductor is the physical wire or conduit that connects the ground electrode system to the electrical system.

Bonding Jumpers

Bonding jumpers are wires or other conductive materials that connect metallic enclosures and equipment together to create an equipotential plane. This is done to prevent differences in electrical potential (voltage) between pieces of equipment and enclosures, which could cause electrical shock or interference. The bonding jumper’s job is to create a path with low impedance that allows current to flow and equalize the electrical potential between the bonded pieces of equipment and enclosures.

Other Conductor Enclosures

This subdivision refers to metallic enclosures and other electrical equipment that may need to be grounded or bonded to prevent electrical shock or interference. This includes things like conduit, cable trays, and junction boxes. Proper grounding and bonding of these enclosures requires a detailed understanding of the electrical safety requirements in the National Electrical Code (NEC).

Equipotential Plane

An equipotential plane is a surface or area of equal electrical potential. In electrical systems, this can be created by bonding metallic enclosures and equipment together with bonding jumpers. The goal of creating an equipotential plane is to prevent differences in electrical potential (voltage) between pieces of equipment and enclosures, which could cause electrical shock or interference. The equipotential plane created by bonding jumpers allows current to flow and equalize the electrical potential between the bonded pieces of equipment and enclosures.

Grounded Systems

Grounded systems refer to electrical systems in which one conductor is intentionally grounded, allowing electrical faults to be safely dissipated or diverted away from electrical equipment and machinery.

Types of Grounded Systems

There are several types of grounded systems that can be found in electrical installations, including:

• Grounded Neutral System: In this system, one conductor, typically the neutral, is connected to ground, ensuring the potential between the neutral and ground remains low.
• Ungrounded System: In this system, none of the conductors are connected to ground, and all conductors are insulated from each other. This method is used for isolated power supply systems, such as in hospitals.
• Grounded Conductor System: This system grounds one phase conductor, which helps to improve the safety of the electrical system, and helps protect equipment and machinery from damage.
• Grounding Electrode Systems: This system uses a grounding electrode to connect the electrical system to the earth. This protects the electrical installation from transient voltage spikes and buildup of static electricity.
• Resistance Grounding System: This system limits the ground fault current to a safe level by connecting a large resistance between the grounding electrode and the electrical system.
• Low-Impedance Grounding System: This system limits the ground fault current by using a low-resistance grounding electrode.

Benefits of Grounded Systems

An electrical system that is correctly grounded offers several benefits, including:

• Protection of Personnel: The primary benefit of grounding a system is to provide a safe path for ground faults and current. This helps protect personnel from electrical shocks and electrocution.
• Equipment Protection: By grounding conductors, electrical equipment and machinery are also protected against damage caused by electrical fault currents.
• Improved System Performance: Electrical systems that are correctly grounded also offer improved performance, fewer electrical surges and dips, and improved grounding helps electromagnetic compatibility (EMC). EMC is needed for safe and reliable operation of equipment and systems that generate significant electromagnetic interference (EMI).
• Compliance with National Electrical Code: Grounding is required by the National Electrical Code (NEC) to ensure that electrical installations meet safety requirements and protect personnel and equipment.

Grounding and Bonding

Grounding and bonding are two essential concepts in electrical installations. Although related, they are not interchangeable and serve different purposes.

• Grounding: Grounding is a safety measure used to protect personnel and equipment from electrical faults. This involves connecting one of the conductors to earth, providing a low-resistance path for fault current.
• Bonding: Bonding is the process of connecting conductive components together, including structural components and electrical equipment. Bonding serves to eliminate differences in potential between conductive components, which can cause electrical arcs and sparks and potential differences that can cause electrical shocks.

Grounding Requirements

The NEC sets out various requirements for grounding and bonding. Some of these requirements include:

• All exposed conductive parts of equipment must be grounded
• Grounding must take place using copper or other highly conductive materials
• Equipment grounding conductors must be sized according to the ratings of the over-current devices protecting the conductors
• All electrical enclosures and equipment must be grounded

Grounded systems are essential for electrical installations to ensure personnel safety, equipment protection, and compliance with national electrical codes. Understanding the different types of grounded systems, the benefits of grounding, and its associated requirements is crucial for the safe and efficient operation of electrical systems.

Overview of Section 250.122

In the National Electrical Code, section 250.122 outlines the requirements for the grounding electrode system and grounding electrode conductor. These requirements are intended to protect people and property from electrical hazards by establishing a low-impedance path for electrical fault current to travel to ground.

Subsection 250.122(A): Electrodes Permitted for Grounding

This subsection outlines the types of electrodes that are permitted to be used for grounding. These may include metal underground water pipe, ground-ring, concrete-encased electrode, grounding electrode conductor, grounding plate, and a ground rod. These are meant to provide a low-impedance path for electrical current to flow to the earth.

Subsection 250.122(B): Materials and Methods

Subsection (B) outlines the minimum requirements for materials and methods used for grounding. This includes the size, type, and installation of the grounding electrode conductor, as well as the materials used for grounding electrodes and their connections. The National Electrical Code requires that these materials be of sufficient size and strength to withstand the expected fault currents and environmental conditions.

Subsection 250.122(C): Installation

This subsection outlines the installation requirements for grounding electrode conductors and grounding electrodes. These requirements are intended to promote safety and ensure that the electrical system can handle expected fault currents. Grounding electrode conductors, for example, must run in as straight a line as possible, have appropriate bonding, and must not have joints or splices unless they are exothermically welded, brazed, or similarly bonded.

Subsection 250.122(D): Grounding Electrode System

Subsection (D) outlines the requirements for the grounding electrode system, which includes all grounding electrodes that are interconnected to form a low-impedance path to ground. This subsection requires that the grounding electrode system be designed to provide a low-impedance path to ground to ensure that any electrical faults are grounded safely.

Subsection 250.122(E): Sizes of Grounding Conductors

This subsection outlines the minimum size requirements for grounding electrode conductors. There are different size requirements for different types of grounding electrodes, and the size must be sufficient to handle fault currents. These requirements are intended to ensure that electrical faults are quickly and safely grounded.

Subsection 250.122(F): Accessibility

Subsection (F) outlines the accessibility requirements for grounding electrode conductors and grounding electrodes. These requirements ensure that grounding electrodes can be easily inspected, tested, and maintained. Accessibility is also important in the event of an electrical fault, as it allows for quick and safe grounding.

Subsection 250.122(G): Bonding of Other Systems

Subsection (G) outlines the requirements for bonding other systems to the grounding electrode system. This includes bonding of metallic piping systems, lightning protection systems, and other equipment that is required to be grounded. The bonding of these systems ensures that they are at the same electrical potential as the grounding electrode system, which helps to prevent electrical hazards.

Conclusion

Section 250.122 of the National Electrical Code outlines the requirements for the grounding electrode system and grounding electrode conductor. These requirements are intended to protect people and property from electrical hazards by establishing a low-impedance path for electrical fault current to travel to ground. By understanding and following the requirements outlined in this section, electricians can ensure that electrical systems are safe and reliable.

Bonding Jumpers

Bonding jumpers are an important component of electrical systems as they are used to connect two or more conductive objects together in order to ensure electrical continuity and bonding to the same electrical potential. The National Electrical Code (NEC) provides guidelines and regulations for the use of bonding jumpers in order to maintain safe and effective electrical systems.

Subsection 250.122(A)

Subsection 250.122(A) specifies that all metal piping systems, including gas piping, that may be exposed to electrical currents are required to be bonded. This is to prevent the hazard of electric shock to individuals who may come in contact with the piping system.

Subsection 250.122(B)

Subsection 250.122(B) details the requirement for bonding of metal framing of buildings. This subsection specifies that all metal framing members of a building or structure must be bonded to an effective grounding electrode system. This is to ensure that all metal parts of the building are at the same potential, thus reducing the risk of electrical shock.

Subsection 250.122(C)

Subsection 250.122(C) pertains to bonding of metal ducts. This subsection requires that all metal ducts that may be exposed to electrical currents are bonded and grounded in order to reduce the risk of electrical shock.

Subsection 250.122(D)

Subsection 250.122(D) outlines the bonding requirements for pools and outdoor spas. This subsection specifies that all metallic parts of these amenities, including the water, must be bonded and grounded in order to reduce the risk of electric shock to swimmers and other individuals who may come into contact with the amenities.

Subsection 250.122(E)

Subsection 250.122(E) pertains to bonding of metal equipment, such as electrical enclosures, switchboards, and panelboards. This subsection specifies that all metal equipment that may be exposed to electrical currents must be bonded and grounded in order to reduce the risk of electric shock to individuals who may come in contact with the equipment.

Subsection 250.122(F)

Subsection 250.122(F) details the bonding requirements for metal-sheathed cables. This subsection specifies that all metal-sheathed cables must be bonded and grounded in order to reduce the risk of electric shock to individuals who may come in contact with the cables.

Subsection 250.122(G)

Subsection 250.122(G) pertains to bonding of metal raceways. This subsection specifies that all metal raceways that may be exposed to electrical currents are required to be bonded and grounded in order to reduce the risk of electric shock to individuals who may come in contact with the raceways.

Subsection 250.122(H)

Subsection 250.122(H) outlines the requirements for bonding of metal frames of fixed equipment, such as appliances and refrigeration units. This subsection requires that all metal frames of fixed equipment must be bonded and grounded in order to reduce the risk of electric shock to individuals who may come in contact with the equipment.

In conclusion, bonding jumpers serve a critical role in maintaining safe and effective electrical systems. The NEC provides specific guidelines for the use of bonding jumpers in order to ensure that all conductive objects are bonded and grounded, reducing the risk of electric shock to individuals who may come in contact with these objects. It is important for individuals working with electrical systems to have a solid understanding of the regulations and requirements outlined in the NEC in order to maintain safe and effective electrical systems.

Other Conductor Enclosures

When it comes to electrical infrastructure, safety should be the foremost priority. That’s why there are strict guidelines and regulations in place to ensure that all electrical systems are installed and maintained properly. One of these guidelines is provided by the National Electrical Code (NEC) and is detailed in section 250.122, which outlines requirements for grounding and bonding of other conductor enclosures.

Other conductor enclosures refer to conduits, ducts, raceways, or other closed metal structures that contain one or more conductors. These enclosures must be grounded to prevent buildup of hazardous voltages. Grounding helps to provide a low-impedance path for fault currents, protecting people, equipment, and structures from electrical hazards. The NEC provides nine subsections under section 250.122 to ensure proper grounding and bonding practices for various types of other conductor enclosures.

Subsection (a): Raceways, Cable Armors, and Enclosures for Conductors

This subsection applies to conductors that are contained in raceways, cable armors, or enclosures that are metal or other electrically conductive materials. The enclosures must be bonded together and to the grounded system to prevent voltage buildup and potentially hazardous situations. Specifically, all metallic raceways, cable armors, and enclosures must be bonded together and connected to the grounding system.

Subsection (b): Metal Clad Cables

Metal clad cables refer to cables that have a grounding conductor and are surrounded by a metal sheath. This subsection requires the metal sheath or armor to be bonded to the grounding system. This is to ensure that any fault current that could potentially flow on the metal sheath is safely dissipated to the grounding system.

Subsection (c): Communication Wires and Cables

This subsection applies to communication wires or cables that are run in the same conduit or raceway as electric light, power, or Class 1 circuits. The communication wires or cables must be grounded at each end of the conduit or raceway and at intervals not exceeding 600 feet. The grounding must be done by one of the methods specified in NEC section 250.118.

Subsection (d): Metal Air Ducts, Dust Collection Systems, Exhaust Systems, and Other Similar Systems

This subsection includes metal air ducts, dust collection systems, exhaust systems, and other similar systems that have the potential to become energized. These systems must be grounded to prevent accumulation of hazardous voltages. The grounding must be done by one of the methods specified in NEC section 250.118.

Subsection (e): Metal Conduit, Tubing, and Cable Trays

This subsection applies to all metal conduit, tubing, and cable trays that support or contain conductors. These must be electrically connected to each other and to the grounding system. The purpose of this is to prevent voltage buildup and to provide an effective path for the flow of fault currents.

Subsection (f): Integrated Gas Spacer Cable (Type IGS)

This subsection specifies requirements for grounding of Type IGS cable, which has integrated gas spacers to separate the conductors and reduce the likelihood of electrical arcing. This type of cable must be grounded in accordance with NEC section 250.118. Additionally, there must be a specified distance between the exposed metal components of adjacent cables to prevent contact and possible arcing.

Subsection (g): Metal Partitions and Walls

This subsection relates to metal partitions and walls that separate electrical equipment or conductors from other spaces. These partitions and walls must be grounded to the grounding system, and there must not be any insulating materials that would prevent proper grounding. The purpose of this is to prevent voltage buildup and to ensure that there is a low-impedance path for any fault currents.

Subsection (h): Metal Frames of Buildings

This subsection is applicable to buildings that have metal frames or structural members that could become energized in the event of a fault. The metal frames must be grounded to the grounding system by one of the methods specified in NEC section 250.118. This is to ensure that there is a low-impedance path for fault currents, preventing potential hazards.

Subsection (i): Exposed Structural Steel

This subsection applies to exposed structural steel that is part of the electrical grounding system. The exposed steel must be bonded to the grounding system in accordance with NEC section 250.118. This is to ensure that the exposed steel is at the same potential as the grounding system and that there is a low-impedance path for any fault currents.

There are multiple types of other conductor enclosures, and each one has its own specific grounding and bonding requirements. The nine subsections outlined in section 250.122 serve as a comprehensive guide to ensure that all other conductor enclosures are grounded properly and that any potential hazards are mitigated. By following these guidelines, electrical professionals can help ensure that all systems are safe and reliable.

Equipotential Plane

Section 250.122 of the National Electrical Code (NEC) contains the regulations for grounding and bonding of electrical systems. This section is one of the most important sections for ensuring safety in electrical installations. It provides guidelines for the grounding and bonding of electrical systems and the precautions necessary to prevent electrical shock hazards.

In order to ensure safety, it is important to maintain equipotential planes in a variety of settings. These planes refer to surfaces within a structure or system that are kept at the same potential, or voltage. Ensuring that equipotential planes are maintained minimizes any differences in potential that could cause electric shock, and prevents damage to electronic equipment from power surges.

The following are the ten subsections of section 250.122:

1. Building or Structure Disconnecting Means

This subsection establishes requirements for the bonding of metal parts of buildings or structures, including the use of metallic raceways and cables associated with the building’s electrical system.

2. Grounding Electrode System and Grounding Electrode Conductor

This subsection outlines the requirements for grounding electrode systems and grounding electrode conductors. These systems are used to connect electrical equipment and structures to the earth to prevent dangerous voltage levels from developing during faults or lightning strikes.

3. Equipment Grounding Conductors

This subsection provides rules for the use of equipment grounding conductors. These conductors are used to connect non-current carrying metal parts of equipment to the electrical system’s grounding electrode system to reduce the risk of shock hazards.

4. Methods of Equipment Grounding

The methods of equipment grounding are given in this subsection. The equipment grounding conductor should be connected to the grounded conductor and to non-current carrying metal parts of the equipment to ensure the integrity of the grounding path.

5. Ground-Fault Circuit-Interrupter Protection for Personnel

This subsection provides information on ground-fault circuit-interrupter protection for personnel. Ground-fault circuit-interrupters are designed to protect people using electrical equipment by interrupting the electrical circuit when a fault is detected in the circuit.

6. Other Equipment and System Bonding

This subsection highlights how other equipment and systems can be bonded. It provides rules for the connection of metallic components of other equipment, such as piping and ductwork, to the grounding electrode system of an electrical service.

7. Bonding of Electrically Conductive Materials and Other Equipment

This subsection specifies the requirements for bonding electrically conductive materials, such as metal water piping, to the grounding electrode system of an electrical service. It also highlights the bonding of other equipment, including swimming pool and spa equipment, that is in contact with water.

8. Direct-Current Systems

This subsection provides rules for grounding and bonding direct-current systems. This includes requirements for the grounding of the negative conductor of direct-current systems, which must be connected to the grounding electrode system of the electrical service.

9. Separately Derived Systems

This subsection specifies the requirements for grounding and bonding separately derived systems, such as generators. The separately derived system must be grounded and bonded to the grounding electrode system of the electrical service to ensure safety.

10. Transfer Equipment

The last subsection provides for transfer equipment. Transfer equipment must be bonded to the grounding electrode system of the electrical service and the equipment being connected to ensure the integrity of the grounding path. This is particularly important when the equipment being connected is not properly grounded.

Equipotential planes are essential for electrical safety. The ten subsections of section 250.122 highlight the importance of grounding and bonding for electrical systems. Maintaining equipotential planes is critical to preventing electric shock hazards and equipment damage.