January 21, 2015
Flexible cords are used to connect electrical equipment to a power source. Flexible cords may have an electrical plug that connects to a power source or they may be permanently wired into a power source. Extension cords (cord sets), cables, and electrical cords are types of flexible cords.
Flexible cords must be protected from damage; avoid sharp corners and projections. Flexible cords can pass through doorways and other pinch points, if the cords are protected.
Cord sets used with portable electric tools and appliances must be of the three-wire type and must be designed for hard or extra-hard use.
Examples of flexible cords designed for hard or extra-hard use include hard service cord types S, ST, SO, STO and junior hard service, SJ, SJO, SJT, SJTO.
Covers of outlet boxes that have holes through which flexible cord pendants pass must have bushings designed for that purpose or must have smooth, well-rounded surfaces on which the cords bear.
Use flexible cords only for:
Flexible cords must have an attachment plug and must be energized from a receptacle outlet when they are used for connecting portable lamps and appliances, connecting fixed equipment, and connecting appliances that can be easily moved for maintenance and repair.
Identification for grounded conductors. Flexible-cord conductors used as grounded conductors or as equipment-grounding conductors must be distinguishable from other types of conductors.
Marking required for certain cords. Type SJ, SJO, SJT, SJTO, S, SO, ST, and STO cords must not be used unless they are durably marked on the surface with the type designation, size, and number of conductors.
Splices. Flexible cords must be used in continuous lengths without a splice or a tap. Splices in hard service flexible cords (No. 12 or larger) may be repaired if the splice retains the same insulation, outer sheath properties, and usage characteristics of the cord.
Strain relief. Use strain relief when connecting flexible cords so that tension, including tension from the weight of the cord, will not be transmitted to the conductor terminals. Examples of strain relief include knotting the cord, winding with tape, and use of fittings designed for that purpose.
Portable lamps must be wired with a flexible cord and a polarized or grounded attachment plug. If the lamp uses an Edison-based lamp holder, the grounded conductor must be identified and attached to the screw shell and the blade of the plug.
Flexible cords used with temporary and portable lights must be designed for hard or extra-hard use.
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