Overview

A luminaire serves as a complete lighting system, responsible for distributing light, positioning lamps, and protecting them from damage. Rigorous safety features are integrated to mitigate electrical hazards. However, the installation of luminaires in specificlocations, such as roofs and walls, requires additional attention due to their exposure to physical stresses. NEC Section 410.10 outlines the rules for installing luminaires in various locations, including requirements like maintaining a 38mm distance between the roof and the luminaire. While in earlier NEC editions this provision was limited to installations on metal corrugated sheet roof decking, it has been updated in the NEC 2023 to cover luminaire installations on all types of roofs. This revision aims to protect the luminaire from damage during roof works and physical stresses.

Applying the 2023 Code

A luminaire functions as a complete lighting system, incorporating a light source such as a lamp or a combination of lamps, along with the necessary components for its operation. These components are designed not only to effectively distribute light but also to position the lamps and ballast, while also shielding them from damage and facilitating connection to a power supply. Fixtures, lamp holders, and lamps are constructed with safety in mind to prevent any live parts from being exposed to contact, thereby reducing the risk of electrical hazards. Despite these safety measures, installing luminaires in certain locations requires extra care and attention due to inherent electrical risks.

NEC addresses these concerns in Section 410.10, which outlines specific requirements for luminaire installation in various locations and settings. One such requirement, subsection 410.10(F), mandates a minimum distance of 38mm between the roof and a luminaire. In the 2020 edition, NEC only specified this distance for installations under metal corrugated sheet roof decking. However, in the 2023 edition, this regulation was expanded to include all types of roofs. Additionally, installations on metal corrugated sheet roof decking are exempt from this requirement if there is at least 50 mm of concrete on top of the decking. These changes aim to ensure sufficient distance between the roof and luminaires to prevent damage during roof works and other physical stresses.

What’s New for the 2023 NEC?

2020 NEC

(F) Luminaires Installed in or Under Roof Decking

Luminaires installed in exposed or concealed locations under metal-corrugated sheet roof decking shall be installed and supported so there is not less than 38 mm (11/2 in.) measured from the lowest surface of the roof decking to the top of the luminaire.

2023 NEC

(F) Luminaires Installed in or Under Roof Decking

Luminaires installed in exposed or concealed locations under roof decking where subject to physical damage shall be installed and supported so there is not less than 38 mm (11/2 in.) measured from the lowest surface of the roof decking to the top of the luminaire.

Exception: The 38 mm (11/2 in.) spacing is not required where metal-corrugated sheet roof decking is covered with a minimum thickness 50 mm (2 in.) concrete slab, measured from the top of the corrugated roofing.