Molded-On Cordsets: A Cost-Effective, Convenient Solution for Power Distribution

  • December 23, 2010
  • Feature
Cordsets have significantly advanced in industrial applicability over time. The National Fire Protection Agency (NFPA) once considered cordsets “splices”—because they do not consist of continuous conductors—and therefore unusable for power distribution in many industrial applications. In 2002, the NFPA 79 code was revised to permit the use of molded-on cordsets—including quick-disconnect connectors and rugged cable for exposed-run installations—for powering motors, pumps and other machinery. Cordsets can be used in place of conduit and raceways when “installed to closely follow the surface and structural members of the machinery” (NFPA, 2006, 79-6), allowing engineers to design and install a system more efficiently than previous methods. Before this revision to NFPA 79, hard wiring was the primary option for power distribution, and all wires were required to be run through protective conduit to prevent wire damage. To protect the conductors and terminations, junction and pull boxes were frequently used, requiring users to install, support and run raceways from one part of the equipment to the next to power multiple sections simultaneously. In some applications, gutter boxes and other approved wire methods were also used. With limited flexibility and the significant time required for installation, this process resulted in additional equipment costs, and expensive downtime for many users. In addition, when large projects were commissioned at one site and installed at another, teams of electricians were often required to re-assemble the equipment once it was moved to the site of installation. This was also a factor when relocating or reusing equipment. To lessen many of these concerns, molded-on cordsets were introduced with a modular, quick-disconnect design for more efficient installation. In a cordset, all wires are bundled into a single cable clad with a jacket material designed to endure diverse environmental conditions—including water, oil and temperature variability. Cordsets deliver plug-and-play connectivity by eliminating the need for conduit and individual terminations for each wire, Developed to deliver the same crush and impact resistance as conduit, this environmentally protected cable withstands the harshest industrial conditions. It can be used for distributing 15 to 40 Amps of power from one machine to another, including on conveyor lines and other large-scale systems. When used for loads such as motors or pumps, cordsets can lead to a decrease in the equipment replacement time due to this ease of installation. So long as the equipment load and other parameters do not change, molded-on cordsets do not require recommissioning, making relocating, rerouting or servicing of equipment—particularly in areas requiring certification—more convenient and also very cost-effective. Additionally, cordsets do not require the high cost of engineering and labor associated with the installation of conduit and raceways. Labor can be reduced by up to 40 percent by using molded-on cordsets, depending on the scope of the project. Installing the CordsetOnce a type of cordset has been selected to meet any unique environment requirements (such as water resistance or high temperatures), users should consult tables provided within the NFPA 79 code to find the appropriate ampacity of the cordset, which is dependent upon the number and size of the conductors. It is recommended to use one conductor for a protective earth ground, and that it should be as close as practical to the load conductors to reduce impedance in the protective earth circuit in the case of a fault. Some cordsets are designed to include a protective earth ground within the cord itself, which ensures that a protective ground is immediately adjacent, or “as close as practical” to the power conductors. The NFPA 79 code permits cordsets to be exposed on the surface of the system; however, they must be protected from damage that could occur if the cordsets hang loose, droop or are obstructing doors or moving parts during normal everyday use. To prevent movement and maintain support to the equipment, cables should be supported and fastened “every 305 mm (12 in.) in a nonvertical run; every 914 mm (36 in.) in a vertical run; when suspended in air spanning a distance up to 457 mm (18 in.)” (2006, NFPA 79-36). Additional protection measures such as guard railings or walk/drive over protective devices may be used to prevent damage. Another method is to install the cordset in a wireway or deck cover. Sections of individual exposed lengths of cable are allowed in these applications up to 15 meters (50 ft). While terminal blocks and enclosures are not required in cordset installations, cordsets still must be supported at all terminations. This design minimizes pressure caused by the cable pulling downward on the terminations and receptacles, enhancing reliability and reducing failures at these connections. Cable ties, supports or clamps can be used to support both the cable and terminations. To protect workers and prevent a possible snag point for other cables, cable ties should be snug but not over-tightened and cut flush. Throughout the process, users must ensure neither the cable nor the insulation in the selected cordset will be damaged during installation or operation. The addition of service loops or extra length to the cables allows users to easily connect or disconnect the cordset to and from a load or device. For example, a loop may be used to connect a small motor, so that it may be disconnected and removed without requiring the cable itself to be detached. Loops should be kept as small as possible in order to limit space consumption. Quick-disconnect connectors are not intended for disconnection under a load. There should not be power on any connectors with exposed male pins as well, as this would pose a shock hazard. The power should always end on the female connector. Externally mounted receptacles with closure caps must be covered to prevent damage or dirt from entering the devices while unplugged—protecting the cable until it is reconnected. Learn More

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