392.18(H) Cable Trays. Marking.

It is quite common to see cable trays used to carry DC PV source circuits operating over 600 volts. These cable trays require the DANGER marking.
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It is quite common to see cable trays used to carry DC PV source circuits operating over 600 volts. These cable trays require the DANGER marking.

Code Change Summary: New marking requirements were added for cable trays.

When cable trays contain conductors rated over 600 volts they are required to be marked “DANGER — HIGH VOLTAGE — KEEP AWAY” at no further than 10-foot intervals. That hasn’t changed.

What has changed is the way those labels are required to look in order to adequately warn of the impending hazard. In the 2014 NEC®, new text was added requiring that these labels must now comply with 110.21(B).

Now, any time the NEC® requires a hazard marking, and section 110.21(B) is mentioned, the labels must adequately warn of the hazard with effective words, colors or symbols. These labels cannot be handwritten (other than portions of the label that may have variable values or information that is subject to change).

An informational note after 110.21(B) references ANSI Z535.4-2011, Product Safety Signs and Labels which provides guidelines on how proper hazard signs and labels must look. This includes font type and size, color of the label, appropriate use of symbols, if text must be capitalized, which information must come first on the label, and where any supporting information must appear on the label.

A new exception was added to exempt inaccessible equipment in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation.

Below is a preview of the NEC®.  See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2011 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).

2014 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).

Exception: Where not accessible (as applied to equipment), in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation, cable tray system warning notices shall be located where necessary for the installation to ensure safe maintenance and operation.

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392.18(H) Cable Trays. Marking.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following cable trays require danger signs to warn of high voltage conductors in the cable tray?

A: A cable tray containing conductors rated 600 volts or less.
B: A cable tray containing conductors rated 1000 volts.
C: All cable trays.
D: Only ladder type cable trays.
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