392.18(H) Marking.
Code Change Summary: A clarification was made regarding marking of cable trays containing conductors operating over 600 volts.
In the 2017 NEC®, cable trays containing conductors “rated” over 600 volts would require a “Danger” label to warn others that the cable tray contained conductors rated over 600 volts even if all conductors in the cable tray “operate” at 600 volts or less.
Sometimes 1000 volt rated conductors are selected even if the operating voltage of the conductors is 480 volts for example. There is nothing prohibiting an electrical engineer from designing an electrical system above the minimum standards mentioned in the NEC® and selecting a better conductor than what is required.
For example, in a facility where the maximum available voltage is 480 volts, it would be foolish to require danger marking to warn others that the cable tray contained conductors rated over 600 volts if all conductors in the cable tray “operate” at 600 volts or less.
In the 2020 NEC®, the issue has been resolved by replacing the word “rated” with “operating”.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
392.18(H) Marking. Cable trays containing conductors rated over 600 volts shall have a permanent, legible warning notice carrying the wording “DANGER — HIGH VOLTAGE — KEEP AWAY” placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21(B).
2020 Code Language:
392.18(H) Marking. Cable trays containing conductors operating over 600 volts shall have a permanent, legible warning notice carrying the wording “DANGER — HIGH VOLTAGE — KEEP AWAY” placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21(B).