National Electrical Installation Standards

Standards as High as Your Own

?
Monday, March 25, 2019

Question:

Thanks for providing the holy cow and yeah I knew that answers to many interesting questions. I have a question about some protective steel plates. An industrial facility has constructed a 1 foot by 1 foot trough in the concrete floor to be used to install a wire basket cable tray. The trough is installed across a walkway that is used by forklifts and personnel. The trough is covered with plate steel to provide the walking and driving surface. A groove in the trough holds the cover in place.

Power and control cables from a control cabinet to electrical equipment are installed in the tray that is installed in the trough. The power cables are using voltages up to 480 volt. The basket is bonded with an equipment ground.

Are the plate steel covers required to be bonded and secured?

Thanks, An Iowa inspector.

A

Answer:

Hey Iowa Inspector thanks for your question and the compliment. If I understand your example correctly then no. Metal material that is likely to become energized is required to be provided with an effective fault current path as stated in 250.4(A)(5). Unfortunately, the phrase "likely to become energized" is not defined in the NEC but it is described in the NEC Style manual as " the failure of insulation". If the steel plates are separated from the cables in the tray, and will not be deflected downwards by the vehicle traffic, they would not be considered likely to become energized. Bonding the steel plates to the tray can provide additional protection if they were to become energized such as by being deflected to the extent they damaged the cable insulation as sated in the Informational Note to 250.116. Not securing them could also result in an incident if they were moved causing a trip hazard or allowing a vehicle to drop into the "trough".

ABOUT CQD: NECA’s Code Question of the Day (CQD) is a leading National Electrical Code® forum for NECA and the industry. The CQD generates a lively dialogue and relative practical and Code-based responses to an ever-increasing and interactive audience.

IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit NECA-NEIS.org for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

NECA SAFETY PRODUCTS: NECA publishes valuable electrical safety books and CDs for the industry. Visit necanet.org/store to view or purchase NECA safety products.

 CONTACT US: To submit a Code question, subscribe, or unsubscribe from this list, please e-mail: codequestion@necanet.org.