Table 600.33(A)(1) & (2) Applications of Power Limited Cable in Signs and Outline Lighting.
Code Change Summary: New tables were added to address low voltage cables used for sign circuits.
In the 2011 NEC®, a section was added to address LED illuminated sign wiring which was important because of the rapid advancement of Light Emitting Diode technology. At the time, LED was the main up and coming contender in the sign industry. Now, LED is one option out of many for low voltage sign applications.
In the 2017 NEC®, “LED” has been removed from the heading of Section 600.33 and now the section applies to the secondary wiring of “Class 2” Sign Illumination Systems. This allows the section to apply to more than just LED applications.
As well, new tables and references to 600.12(C), 600.24, and 600.33(A), (B), (C), and (D) were added which allow all of the rules for low voltage signs to remain within Article 600, where before, the code reader was referred to Article 725.
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 LED Sign Illumination Systems, Secondary Wiring. The wiring methods and materials shall be installed in accordance with the sign manufacturers installation instructions using any applicable wiring methods from Chapter 3 and the requirements for Class 2 circuits contained in Part III of Article 725, as applicable.
(A) Insulation and Sizing of Class 2 Conductors. Listed Class 2 cable that complies with Table shall be installed on the load side of the Class 2 power source. The conductors shall have an ampacity not less than the load to be supplied and shall not be sized smaller than 22 AWG.
(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 Class 2 Sign Illumination Systems, Secondary Wiring. The wiring methods and materials used shall be in accordance with the sign manufacturers installation instructions using any applicable wiring methods from Chapter 3, Wiring Methods, and the requirements for Class 2 circuits contained in 600.12(C), 600.24, and 600.33(A), (B), (C), and (D).
(A) Insulation and Sizing of Class 2 Conductors. Class 2 cable listed for the application that complies with Table 600.33(A)(1) or Table 600.33(A)(2) for substitutions shall be installed on the load side of the Class 2 power source. The conductors shall have an ampacity not less than the load to be supplied and shall not be sized smaller than 18 AWG.
N (1) General Use. CL2 or CL3, PLTC, or any listed applicable cable for general use shall be installed within and on buildings or structures.
N (2) Other Building Locations. In other locations, any listed applicable cable permitted in 600.33(A)(1), (A)(2), (A)(3), and (A)(4) and Table 600.33(A)(1) and (A)(2) shall be permitted to be used as follows:
(1) CL2P or CL3P — Ducts, plenums, or other spaces used for environmental air
(2) CL2R or CL3R — Vertical shafts and risers
(3) Substitutions from Table 600.33(A)(2)