Article 350 of the National Electrical Code (NEC) 2023 covers the requirements for liquidtight flexible metal conduit (LFMC). This type of conduit is used to protect electrical wires and cables from physical damage and to provide a grounded path for electrical currents in wet or damp environments. LFMC is typically used in commercial and industrial applications where moisture or liquids are present.
The NEC provides detailed guidelines for the installation and use of LFMC to ensure the safety and reliability of electrical systems. The requirements outlined in Article 350 cover the materials, dimensions, installation, and maintenance of LFMC.
Materials
The materials used to manufacture LFMC must comply with the requirements set forth in Article 350. LFMC is typically made of steel or aluminum, and it must be flexible enough to bend around obstacles and corners without breaking or kinking. The conduit must also be coated or covered with a liquidtight jacket to prevent moisture or liquids from penetrating the conduit and damaging the wires inside.
The NEC requires that LFMC be free from any defects that could affect its strength or flexibility, such as cracks, splits, or holes. The conduit must also be able to withstand the stresses and strains of the installation process and normal use in wet or damp environments.
Dimensions
Article 350 sets forth specific dimensions for LFMC to ensure its compatibility with other electrical components and to facilitate proper installation. The diameter of LFMC must be at least 3/8 inch, and it cannot exceed 6 inches. The walls of the conduit must be uniform in thickness and cannot be less than the minimum values specified in the NEC.
Installation
Proper installation of LFMC is essential for the safety and reliability of electrical systems in wet or damp environments. Article 350 provides detailed guidelines for the installation of LFMC, including the use of fittings, supports, and expansion joints.
Fittings
Fittings are used to connect sections of LFMC and to change the direction of the conduit. The NEC requires that fittings be made of the same material as the conduit and that they be compatible with the type and size of the conduit being used. Fittings must also be installed in accordance with the manufacturer’s instructions and the requirements of the NEC.
Supports
LFMC must be supported at regular intervals to prevent sagging and to ensure proper alignment. The NEC specifies the maximum distance between supports based on the size and weight of the conduit. Supports must be made of materials that are compatible with the conduit and must be securely attached to the building structure.
Expansion Joints
Expansion joints are used to compensate for the expansion and contraction of the conduit due to temperature changes. The NEC requires that expansion joints be installed at intervals determined by the manufacturer or engineer, based on the length and temperature range of the conduit. Expansion joints must also be compatible with the material and size of the conduit.
Bending
LFMC can be bent to follow the contours of the installation area. The NEC specifies the minimum radius of bends based on the size and type of conduit being used. Bends must also be made in accordance with the manufacturer’s instructions and the requirements of the NEC.
Grounding
LFMC must be grounded to provide a safe path for electrical currents. The NEC requires that LFMC be connected to a grounding conductor using approved fittings and connectors. The grounding conductor must also be continuous and unbroken.
Maintenance
Regular maintenance is important to ensure the continued safety and reliability of LFMC. Article 350 requires that LFMC be inspected periodically to ensure that it is free from defects, corrosion, and other damage. Any damaged or defective conduit must be replaced immediately to prevent hazards.
Conclusion
Article 350 of the NEC 2023 provides detailed guidelines for the installation and use of liquidtight flexible metal conduit. This type of conduit is widely used in commercial and industrial applications where moisture or liquids are present. The requirements set forth in Article 350 cover the materials, dimensions, installation, and maintenance of LFMC to ensure the safety and reliability of electrical systems in wet or damp environments.
It is essential to follow the guidelines set forth in Article 350 to ensure the proper installation and use of LFMC. Failure to do so can result in hazards such as electrical shock, fire, and damage to equipment. Regular maintenance is also important to prevent damage and ensure the longevity of the conduit. By following the guidelines set forth in Article 350, electrical professionals can ensure the safe and reliable use of LFMC in their installations.
Liquidtight flexible metal conduit has several advantages over other types of conduit in wet or damp environments. LFMC provides a liquidtight seal that prevents moisture or liquids from penetrating the conduit and damaging the wires inside. It is also flexible and easy to install, making it a popular choice for many applications.
When choosing between different types of conduit for wet or damp environments, it is important to consider the specific requirements of the installation and to consult the NEC guidelines. In some cases, a combination of LFMC and other types of conduit may be necessary to provide the optimal level of protection and flexibility.
In conclusion, Article 350 of the NEC 2023 provides important guidelines for the installation and use of liquidtight flexible metal conduit. LFMC is a versatile and reliable option for protecting electrical wires and cables in wet or damp environments. By following the guidelines set forth in Article 350, electrical professionals can ensure the safe and reliable use of LFMC in their installations.