Class 1, Section 2 electrical requirements are part of the National Electrical Code (NEC) and are designed to ensure safety in hazardous locations where flammable gases, vapors, or liquids may be present. Category 1 locations deal with gases or vapors, and Category 2 refers to environments where these substances do not occur naturally but can exist under abnormal conditions, such as during leaks or equipment failure. The main electrical requirements for such environments are as follows:
Equipment design and installation:
Explosion-proof equipment: Electrical enclosures and appliances must be explosion-proof to prevent sparks or heat from igniting flammable gases or vapors. However, since Section 2 indicates that hazardous materials are not present under normal conditions, the equipment may not need to be fully explosion-proof but must be designed to prevent ignition in the presence of gases.
Sealed or disinfected containers: Equipment that can generate sparks or heat must be placed in sealed or disinfected containers to prevent contact with hazardous atmospheres.
Intrinsically safe circuits: Low-energy circuits that are unable to cause ignition can be used, even in the presence of hazardous atmospheres.
Wiring methods:
Wiring in Class 1 and Division 2 areas must reduce the risk of gas migration and prevent sparks or heat from reaching hazardous atmospheres. The following wiring and cable methods are approved for use:
Rigid Metal Conduit (RMC): Commonly used in Class 1 and Section 2 installations, RMC provides robust protection for conductors and can contain any internal explosion. Proper sealing is essential at the boundaries between classified and unclassified areas.
Intermediate Mineral Conduit (IMC): Lighter than RMC but provides similar protection. It is often used for hazardous areas that have the same sealing requirements as RMC.
Electrical Metal Tube (EMT): EMT can be used in Class 1 and Section 2 areas if compression type fittings are used to ensure a tight seal. EMT is more economical and easier to install than RMC or IMC but must follow specific NEC guidelines to prevent gas migration.
Rigid non-metallic conduit (RNC) and Flexible Non-Metallic Conduit (FNC) They can be used if specifically listed for hazardous locations. Lightweight, cost-effective and great for corrosion resistance, FNC is used in environments where movement or vibration occurs. Non-metallic ducts must be installed with gas-tight fittings specifically listed for hazardous locations. These fittings prevent dangerous gas from being transmitted through the duct system.
MI cable type (metal insulated): MI cables consist of a solid copper sheath and mineral insulation, providing high mechanical resistance and fire resistance. It is well suited to hazardous locations due to its sturdy, gas-tight construction. It provides maximum protection
MC cable type (metal clad): MC cables They are accepted on Class 1, Section 2 sites when equipped with a continuous gas tight enclosure, and are not used without them. These cables must be terminated with approved fittings that prevent gas migration. MC-HL (Hazardous Location) The cables provide enhanced protection with a metal shield and sealed construction, making them ideal for hazardous environments.
Type TC (tray cable): Chinese cables It can be used in Class 1 and Section 2 areas if installed in conduits or cable trays that comply with hazardous location standards. It is essential to properly close any exposed sections of the stairs.
Additional cable types for Category 1, Division 2:
Type ITC (Instrumentation Tray Cable): ITC cables are used for control circuits, feature flame-resistant and shielded designs, and are ideal for Class 1 and Section 2 environments when enclosed in cable trays or conduits.
Type PLTC (Limited Power Tray Cable): Designed for circuits with limited power, PLTC cables are permitted in Class 1, Division 2 areas when installed in conduits or trays with a protective seal.
Type XHHW-2 (high temperature waterproof and threaded): These cables They are commonly used in industrial wiring with cross-linked polyethylene insulation that provides heat, water and chemical resistance. XHHW-2 cables are acceptable for hazardous locations when installed in approved conduits.
Sealing requirements:
Channel systems: Sealing devices must be installed at specific points, for example, within 18 inches of the fence boundary, to prevent the migration of flammable gases or vapors through the duct system into unclassified areas.
Bonding and grounding:
in Class 1, Section 2 Zones, grounding and bonding are essential for safety. The main components that should be grounded or bonded include:
Channel systems (eg, RMC, IMC, EMT).
Packages (junction boxes, control panels).
Electrical equipment (Motors, transformers and lighting fixtures).
Cable trays (If the metal is C).
Bonding jumpers To ensure continuity between metal components.
Flexible metal conduits and cables.
Non-metallic channel (Metal parts such as fittings must be grounded.)
Metal structures and supports (For example, shelves and frames).
Grounding electrodes To dissipate fault current safely.
