NEC Article 312 provides comprehensive requirements for the installation and construction of cabinets, cutout boxes, and meter socket enclosures. This article ensures these enclosures are used and installed correctly to maintain the safety and reliability of electrical systems. Here is an overview of NEC Article 312:

312.1 Scope

This section establishes the scope of Article 312, which covers the installation and construction specifications for cabinets, cutout boxes, and meter socket enclosures. It does not apply to equipment operating at over 1000 volts unless specifically referenced elsewhere in the code.

312.2 Damp and Wet Locations

In damp or wet locations, surface-type enclosures must be placed or equipped to prevent moisture or water from entering and accumulating within the cabinet or cutout box. There must be at least a 6 mm (1/4 inch) airspace between the enclosure and the supporting surface to prevent moisture ingress.

312.3 Installation

Specifies the requirements for installing cabinets, cutout boxes, and meter socket enclosures, ensuring they are securely and properly mounted to prevent physical damage and ensure accessibility.

312.4 Repairing Noncombustible Surfaces

Any non-combustible surfaces that are broken or incomplete must be repaired so there’s a maximum 1/4 inch gap at the edge of a cabinet or cutout box employing a flush-type cover.

312.5 Conductors Entering Enclosures

Conductors must enter enclosures through proper fittings to protect and secure the cables and wiring. This rule is critical to prevent physical damage and ensure safe operation.

312.6 Wire-Bending Space

Tables 312.6(A) and 312.6(B) provide the minimum wire-bending space requirements at terminals and the minimum width of wiring gutters based on the wire size and the number of wires per terminal. These requirements ensure that conductors are installed without undue stress and have adequate space for bending.

312.7 Space in Enclosures

Cabinets and cutout boxes must have approved space to accommodate all conductors installed in them without crowding, ensuring safe operation and maintenance.

312.8 Enclosures for Switches or Overcurrent Devices

The wiring space within enclosures for switches or overcurrent devices can be used for splicing, tapping, or feed-through conductors, provided certain conditions are met:

• The total of all conductors at any cross-section of the wiring space must not exceed 40% of the cross-sectional area.
• The total area of all conductors, splices, and taps must not exceed 75% of the cross-sectional area.
• A warning label must be applied to identify the closest disconnecting means for any feed-through conductors.

312.10 Screws or Other Fasteners

Screws or other fasteners used in the field that enter wiring spaces must be provided by or specified by the manufacturer. They should have blunt ends to prevent damage to conductors and insulation.

312.11 Construction Specifications

Specifies the material requirements for cabinets, cutout boxes, and meter socket enclosures, ensuring they are constructed from materials that provide adequate protection from corrosion and physical damage. This section includes requirements for metal and nonmetallic enclosures, ensuring they meet strength and rigidity standards.

For more detailed information and context, referring to the NEC Handbook and other resources provided by the NFPA is highly recommended. Sources for this summary include information from iBidElectric and CodeBookCity.