Article 393 Low-Voltage Suspended Ceiling Power Distribution Systems.
Code Change Summary: A new article on low voltage suspended grid ceiling systems was created to make room for new technology.
A day is coming where relocating a 2X4 lay in light to a different spot in a suspended grid ceiling will be as easy as pushing it up through the grid and moving it wherever it is more convenient without the need to relocate a power whip or junction box.
Certain main grid ceiling runners will be energized from a nearby power server module that provides low voltage to supply specific low voltage luminaires and devices mounted in the ceiling.
A Low-Voltage Suspended Ceiling Power Distribution System is defined in 393.2 as “a system that serves as a support for a finished ceiling surface and consists of a busbar and busbar support system to distribute power to utilization equipment supplied by a Class 2 power supply”.
The new article specifies certain listing requirements, installation methods, used permitted, used not permitted, associated definitions, securing, supporting, grounding and more.
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).
2014 Code Language:
393.10 Uses Permitted. Low-voltage suspended ceiling power distribution systems shall be permanently connected and shall be permitted as follows:
(1) For listed utilization equipment capable of operation at a maximum of 30 volts ac (42.4 volts peak) or 60 volts dc (24.8 volts peak for dc interrupted at a rate of 10 Hz to 200 Hz) and limited to Class 2 power levels in Chapter 9, Table 11(A) and Table 11(B) for lighting, control, and signaling circuits.
(2) In indoor dry locations.
(3) For residential, commercial, and industrial installations.
(4) In other spaces used for environmental air in accordance with 300.22(C), electrical equipment having a metal enclosure, or with a nonmetallic enclosure and fittings, shall be listed for use within an air-handling space and shall have adequate fire-resistant and low smoke- producing characteristics and associated wiring material suitable for the ambient temperature.
393.12 Uses Not Permitted. Suspended ceiling power distribution systems shall not be installed in the following:
(1) In damp or wet locations.
(2) Where subject to corrosive fumes or vapors, such as storage battery rooms.
(3) Where subject to physical damage.
(4) In concealed locations.
(5) In hazardous (classified) locations.
(6) As part of a fire-rated floor-ceiling or roof-ceiling assembly, unless specifically listed as part of the assembly.
(7) For lighting in general or critical patient care areas.