NEC Article 110 provides comprehensive requirements for the installation of electrical conductors and equipment to ensure safety and reliability. This article spans sections 110.1 to 110.26 and covers a wide range of general requirements crucial for electrical installations. Here is a detailed overview of NEC Article 110:
110.1 Scope
This section specifies the scope of NEC Article 110, covering the general requirements for the examination and approval, installation and use, access to, and spaces about electrical conductors and equipment; the enclosures for electrical conductors and equipment; and the general conditions of operation.
110.2 Approval
All electrical conductors and equipment required or permitted by the NEC must be approved by the authority having jurisdiction (AHJ), ensuring compliance with safety standards.
110.3 Examination, Identification, Installation, and Use of Equipment
- 110.3(A) Examination: Electrical equipment must be installed and used in accordance with its listing, labeling, and the manufacturer’s instructions.
- 110.3(B) Installation and Use: Equipment must be installed and used in a manner consistent with the manufacturer’s listing and labeling instructions.
110.4 Voltages
The voltage ratings of electrical equipment must match the nominal voltage of the system in which the equipment is installed, ensuring compatibility and safety.
110.5 Conductors
Conductors used in electrical installations must be made of copper, aluminum, or copper-clad aluminum, unless otherwise specified by the NEC.
110.6 Conductor Sizes
Conductor sizes must be specified in American Wire Gauge (AWG) or circular mils, providing standardized measurements for electrical installations.
110.7 Wiring Integrity
Completed electrical wiring installations must be free from short circuits, ground faults, and other electrical faults to ensure operational safety.
110.8 Wiring Methods
Wiring methods must be suitable for the location and conditions of use, considering factors such as insulation type, temperature ratings, and environmental conditions.
110.9 Interrupting Rating
Electrical equipment intended to interrupt current at fault levels must have an adequate interrupting rating to handle the maximum current it may need to interrupt.
110.10 Circuit Impedance and Other Characteristics
Overcurrent protective devices and other circuit components must be selected and coordinated to ensure they can handle the electrical load without extensive damage in case of a fault.
110.11 Deteriorating Agents
Electrical equipment must be protected from environmental factors such as chemicals, moisture, and physical damage to ensure long-term reliability and safety.
110.12 Mechanical Execution of Work
Electrical installations must be performed in a neat and workmanlike manner, with proper securing and supporting of conductors and cables.
110.13 Mounting and Cooling of Equipment
- 110.13(A) Mounting: Electrical equipment must be securely mounted to ensure stability.
- 110.13(B) Cooling: Adequate cooling must be provided to prevent overheating and ensure safe operation.
110.14 Electrical Connections
- 110.14(A) Terminals: Connections must ensure a secure, undamaged connection of conductors to terminals.
- 110.14(B) Splices: Conductors must be spliced using methods suitable for the application, such as splicing devices, brazing, welding, or soldering.
110.15 High-Leg Marking
In 4-wire, delta-connected systems, the phase with the higher voltage to ground must be clearly marked with orange to identify it as the high-leg.
110.16 Arc-Flash Hazard Warning
Electrical equipment likely to require examination, adjustment, servicing, or maintenance while energized must be marked to warn qualified persons of potential arc-flash hazards.
110.21 Marking
- 110.21(A) Manufacturer’s Markings: Equipment must be marked with the manufacturer’s name, trademark, or other identification.
- 110.21(B) Field-Applied Markings: Field-applied markings must be durable and suitable for the environment involved.
110.22 Identification of Disconnecting Means
Each disconnecting means must be legibly marked to indicate its purpose, unless the purpose is evident from the location and arrangement.
110.23 Current Transformers
Where current transformers are used, they must be marked with their rating and use to ensure proper identification and safety.
110.24 Available Fault Current
Service equipment in non-dwelling units must be marked with the maximum available fault current to ensure proper selection and coordination of protective devices.
110.26 Spaces About Electrical Equipment
- 110.26(A) Working Space: Adequate working space must be provided around electrical equipment for safe operation and maintenance.
- 110.26(B) Clear Spaces: Clear spaces must be maintained to allow for safe working conditions.
- 110.26(C) Entrance to and Egress from Working Space: Safe entry and exit routes must be provided for areas containing electrical equipment.
- 110.26(D) Illumination: Working spaces must be well-lit to ensure visibility and safety during operations and maintenance.
- 110.26(E) Headroom: Sufficient headroom must be provided above working spaces to allow for safe movement and operation.
Conclusion
NEC Article 110 sets forth essential requirements for the installation and maintenance of electrical systems, ensuring safety, reliability, and compliance with established standards. These comprehensive guidelines help prevent electrical hazards and ensure the integrity of electrical installations.
For more detailed information and further context, referring to the NEC Handbook and other resources provided by the NFPA is highly recommended.