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Barriers at Service Panelboards

New requirements added for barriers to be placed in all service panelboards such that no uninsulated, ungrounded service busbar or service terminal be exposed to inadvertent contact by persons Identified as a safety concern by installers and proponents of electrical safety in the workplace An exception was also added eliminating the barriers at panelboards installed to comply with the requirements of 408.36, Ex. No. 1, 2, and 3 Exceptions to 408.36 address the “six means of disconnect” rules and the old “split‐bus” panelboards that could be present.

Exception: This requirement shall not apply to service panelboards with provisions for more than one service disconnect within a single enclosure as permitted in 408.36, Exceptions No. 1, 2, and 3

This code change requires a careful read in order to grasp what occurred. Public input No. 1888-NFPA 70-2014 was the main contributor that resulted in the major changes to Article 411.

In the 2014 NEC, revisions to the title and content in Article 411 acknowledged that the article included lighting equipment connected to a Class 2 power source. Part of the 2014 revisions included a reference in 411.3(B) requiring listed Class 2 lighting equipment to be rated in conformance with Chapter 9, Table 11(A) or Table 11(B). Those tables provide the maximum power limits for a Class 2 power supply and are far too restrictive to be applied generally to all low voltage lighting installations using a Class 2 power transformer.

Based on the 2014 requirements and the restrictions in Chapter 9 Tables 11(A) and 11(B), a small and simple low voltage lighting installation, such as those commonly installed under the kitchen cabinets, might require several Class 2 power supplies in order to comply with the code language and stay within the maximum power requirements for a Class 2 power supply. All with little or no increased safety levels. Listed Class 2 power supplies are evaluated for fire and shock hazards regardless of maximum output ratings.

In the 2017 NEC, the article title has been changed to Low Voltage Lighting and many of the previous Class 2 references were removed.

Below is a list of a few important changes to Article 411:

Article title changed to “Low-Voltage Lighting”.
411.3 The output circuits of the power supply shall be rated for 25 amperes maximum under all load conditions instead of 25 amperes and 30 volts (42.4 volts peak) maximum as previously required in the 2014 NEC.
Confusing language about lighting “systems” in 411.4(A) and 411.4(B) was clarified or removed.
Nine different references to “Class 2” throughout the Article were reduced to three so as only to reference Class 2 where necessary and avoid confusion.