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NEC ARTICLE 409

Over the past decade, industrial control manufacturers have made innovative component changes to improve the electrical safety of their products. A few examples include finger-safe guarding, arc-flash barriers and the determination, labelling and proper documentation of a component’s short circuit current rating.

Coincidently, federal and state governments began adopting more rigid compliance requirements affecting OEM machinery, contractor installations and inspections by the local authorities at the end-use facilities. The first major change appeared in the 2005 National Electric Code which listed a new paragraph - Article 409 - pertaining to “the manufacture of industrial control panels”. This article referenced the Underwriters Laboratories “UL508a” standard which defines UL approved methods to be used in the manufacture of industrial control panels. Article 409 recommends general manufacturing methods with a focus on short circuit ratings and the proper labeling of an industrial control panel, which correlates directly to the procedures described in the UL508a standard. After 2005, individual states began to incorporate the NEC requirements into their state building and construction codes, however, legal enforcement and inspection was regulated differently from state to state. As of January 2016, all but three states - Arizona, Mississippi, and Missouri - have made the NEC part of their formal construction codes.

An additional step to improve safety came in the form of compliance and enforcement. To offset the higher demand for inspections and certifications, United Laboratories initiated a training and certification program to allow industrial manufactures like Trola Industries, Inc. to design, build, and apply the UL508a label to electrical control panels at their plants.


Examples of how UL508a standards impact control panel design and manufacturing:


  1. Calculate short circuit current rating (SCCR) for entire control panel. The calculated rating is to be shown on a label located within that control panel.

  2. Proper use and location of E-Stop buttons with yellow legend plates.

  3. Provide label information indicating system voltage and motor full-load amps.

  4. Alphanumeric references to the drawings used to manufacture the control panel.

  5. Include “As-Built” drawing set inside the control panel when it is shipped.

  6. Arrange components in the control panel following the minimum air-space requirements determined by spacing UL used to test and list individual component.

  7. Provide labels indicating proper torque ratings on mechanical or electrical connections as specified by the component manufacturer.

  8. Provide labels indicating proper size and type of fuses to be used for maintenance.

  9. Grounding and bonding methods.

  10. Wiring sizes and color schemes.

ARC-FLASH WORKER PROTECTION

On August 13, 2007, the Occupational Safety and Health Administration (OSHA) enacted a new law under NFPA-70E calling for the protection of workers potentially exposed to the dangers of arc-flash explosions resulting from a short circuit condition inside electrical equipment containing voltage potentials of 50 or more volts. This pertains to workers who are involved in an installation or maintenance function requiring them to work where there is voltage present or where the potential for voltages exist (i.e. a control panel connected to a “live” voltage source that has not been disconnected and locked out for service).

The written law places the burden of responsibility on the company to develop and enforce a set of management responsibilities and policies applicable to their personnel or outside contractors who may work on or nearby electrical equipment at their facilities. This electrical equipment includes, but is not limited to, industrial control panels, motor control centers and circuit breaker panelboards.


Examples of these responsibilities include:


  1. Establishment of written policies on arc-flash protection safeguards for employees and outside contractors.

  2. Provide training to personnel resulting in certification that said personnel have been educated to the dangers of arc-flash and are knowledgeable of the proper levels of protective clothing or gear required to work at various voltage levels. Certification cards are issued after completion of training.

  3. Provide readily visible warning labels on the exterior surface of equipment as to the potential electrical dangers that may exist when working on the equipment.

Article 409 in the 2005 NEC and OSHA’s NFPA 70E have created a new standard of performance for everyone involved in the effort to create a safer work environment. Prevention of accidents starts with awareness and education, followed by changes in behavior and attitudes about safety. Trola Industries, Inc would encourage everyone to research these new provisions in the law and include them in their standard procedures.