Code Change Summary: New Article for Flexible Bus Systems.
In the 2023 NEC®, New Article 371 was added to provide requirements for Flexible Bus Systems.
According to Article 100 definitions, flexible bus systems are an assembly of flexible insulated bus, with a system of associated fittings used to secure, support, and terminate the bus.
Flexible bus systems use a flat braided insulated conductor that provides greater flexibility than busduct without the bending radius limitations typical cables have. Flexible bus systems are engineered systems designed for a specific site location and are ordinarily assembled on site with the components furnished or specified by the manufacturer.
Highlights from new Article 371 include:
- New Section 371.6 requires flexible bus systems to be listed but at the time the new article was created, the associated product standard and outline of investigation was still under development.
- New Section 371.10 permits flexible bus systems for the following uses:
- For services, feeders, and branch circuits
- For indoor use
- For outdoor use if identified for outdoor use
- For installation in corrosive, wet, or damp locations where identified for such use
- Exposed
- Behind access panels where the space behind the access panel is not used for air-handling purposes
- To penetrate through walls and floors in accordance with 371.18
- New Section 371.12 does NOT permit flexible bus systems to be used in hoistways, in air handling spaces, where exposed to physical damage, or in hazardous locations unless specifically allowed in NEC® Chapter 5.
- New Section 371.14 requires flexible bus systems to be designed for jobsite specific applications by a qualified engineer in accordance with the limits of the listing and manufacturer’s installation instructions.
- New Section 371.30(C) permits flexible bus systems to be installed in support trays supplied as associated fittings for the listed flexible bus system. Support trays for flexible bus systems are not required to be continuous.