NEC Article 408 outlines the requirements for the installation, construction, and use of switchboards, switchgear, and panelboards. These components are crucial for managing and distributing electrical power safely and efficiently. Here is a comprehensive overview of NEC Article 408:

408.1 Scope

This section covers the general requirements for switchboards, switchgear, and panelboards, ensuring they are installed and used safely in various electrical systems.

408.2 Definitions

Defines key terms such as “switchboard,” “switchgear,” and “panelboard” to ensure clarity and consistency within the article.

408.3 Field Identification Required

Switchboards, switchgear, and panelboards must be clearly marked to indicate their purpose and the source of power. This includes:

• 408.3(A) Circuit Directory or Circuit Identification: Every circuit and modification must be legibly identified with specific descriptions at each switch or circuit breaker.
• 408.3(B) Source of Supply: Devices must be marked to indicate where the power originates, with durable, permanent labels.

408.4 Circuit Directory

Each circuit and modification must be identified as to its purpose or use, and the circuit directory should be located on or adjacent to the panel door for panelboards, and at each switch or circuit breaker for switchboards and switchgear.

408.5 Clearance for Conductor Entering Bus Enclosures

Specifies the clearance requirements for conductors entering bus enclosures to ensure safe installation and prevent damage.

408.6 Short-Circuit Current Ratings

Switchboards, switchgear, and panelboards must have a short-circuit current rating not less than the available fault current. The available fault current and the date of the calculation must be marked on the enclosure at the point of supply for non-residential units.

408.7 Unused Openings

Unused openings for circuit breakers and switches must be closed using identified closures or other approved means to provide protection equivalent to the enclosure wall.

408.8 Reconditioning of Equipment

Specifies conditions under which reconditioning of switchboards and switchgear is allowed, while prohibiting the reconditioning of panelboards. Reconditioned equipment must meet specific standards and be labeled accordingly.

408.18 Clearances

Specifies clearances required for switchboards, switchgear, and panelboards, including:

• 408.18(C) Connections: Equipment requiring rear or side access for connections must be marked accordingly and must comply with clearance requirements for safe installation and operation.

408.30 Overcurrent Protection for Panelboards

Panelboards must be protected by an overcurrent protective device not exceeding the panelboard’s rating. This device can be located within or on the supply side of the panelboard. Exceptions are provided for certain configurations, such as service equipment with multiple disconnecting means.

408.36 Overcurrent Protection

In addition to the requirements in Article 408.36, an overcurrent protective device with a rating not greater than that of the panelboard itself must protect a panelboard. This device should be located within or at any point on the supply side of the panelboard.

408.38 Enclosure

Panelboards must be mounted in cabinets, cutout boxes, or identified enclosures and must be dead-front. Where the available fault current exceeds 10,000 amperes, the panelboard and enclosure combination must be evaluated for the application to ensure safety and compliance.

408.43 Panelboard Orientation

Panelboards must not be installed in the face-up or face-down position. This requirement addresses safety concerns related to debris, liquid ingress, and the difficulty of providing safe working space.

408.50 Grounding and Bonding

Switchboards, switchgear, and panelboards must be properly grounded and bonded to ensure safety. Metal parts of the equipment must be connected to the equipment grounding conductor to provide a continuous path for fault currents.

408.54 Grounded Conductor Terminations

This section requires that grounded conductors terminate within the same enclosure where the grounding conductor is installed. This ensures that the grounded conductor is properly connected and accessible for maintenance and inspection.

408.56 Circuit Directory

A directory must be provided for each switchboard, switchgear, and panelboard to identify the circuit served by each overcurrent device. This directory must be legible and permanently installed on the face or inside of the equipment door.

408.58 Panelboard Orientation

Panelboards must not be installed in the face-up or face-down position. This requirement addresses safety concerns related to debris, liquid ingress, and the difficulty of providing safe working space.

408.60 Marking of Switchboards and Panelboards

Switchboards and panelboards must be marked with the manufacturer’s name, voltage, current rating, and other pertinent details. This ensures that the equipment can be properly identified and used within its specified limits.

Summary of Key Requirements

• Grounding and Bonding: All metal parts must be grounded and bonded.
• Grounded Conductor Terminations: Must terminate within the same enclosure.
• Circuit Directory: Must be provided and permanently installed.
• Orientation: Panelboards must not be installed face-up or face-down.
• Marking: Must include manufacturer’s name, voltage, and current rating.

For more detailed information, consulting the NEC Handbook and additional resources provided by the NFPA is highly recommended. More insights can be found on resources like Electrical License Renewal and Breaker & Fuse.