600.33(A)(3,4) Low Volt Cable Marking Requirements.
Code Change Summary: Requirements for Class 2 cables used for signs have been revised.
Section 600.33(A)(3) and (4) provide rules on Class 2 cables used for sign installations. These conductors are run from the load side of a Class 2 power supply to the sign letters.
In the 2014, NEC®, the code language was subjective and provided no real sense of direction. The previous wording allowed cables in wet locations to be either identified for use in wet locations or have a moisture-impervious metal sheath. This left many still wondering what could be used; Especially for rooftop installations on the back side of a parapet wall where low volt cables are installed to supply a sign on the other side of the wall.
In the 2017 NEC®, the rules are clear:
- For wet locations, Class 2 cables shall be listed and marked suitable for use in wet locations.
- Where exposed to sunlight, Class 2 cables shall be listed and marked sunlight resistant suitable for outdoor use.
Knowing what exactly is required to be marked on a cable used in a specific location helps the installer and inspector to know if the correct wiring method has been installed.
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 2017 NEC® edition of NFPA 70.
2014 Code Language:
600.33(A)
(1) Wet Locations. Class 2 cable used in a wet location shall be identified for use in wet locations or have a moisture-impervious metal sheath.
(2) Other Locations. In other locations, any applicable cable permitted in Table 725.154 shall be permitted to be used.
2017 Code Language:
600.33(A)
(3) Wet Locations. Class 2 cable used in a wet location shall be listed and marked suitable for use in a wet location.
(4) Other Locations. Class 2 cable exposed to sunlight shall be listed and marked sunlight resistant suitable for outdoor use.