Overview

Flexible Bus Systems (FBS) provide a flexible, compact, and high-capacity solution for electrical connections

in the power industry. Despite their advantages, previous editions of the NEC did not address their usage or limitations due to their recent introduction to the industry. Sections 371.10 and 371.12 were included in the 2023 edition, permitting the use of FBS systems in a range of indoor and outdoor applications. However, their deployment in hazardous areas and locations prone to physical damage is restricted. These new provisions ensure the safe and appropriate deployment of FBS systems, thereby enhancing the overall reliability of electrical systems.

Applying the 2023 Code

Flexible bus systems (FBS) have recently emerged in the power industry as a flexible and high-capacity connector solution. These systems consist of flexible conductors housed within insulated enclosures, arranged in a layered structure. They offer several advantages over traditional rigid bus systems, including easy installation in confined spaces, around corners, and through obstacles. Additionally, FBS systems demonstrate reduced installation time, improved flexibility, and enhanced scalability compared to conventional bus systems. However, despite their versatility, it’s important to recognize that FBS may not be suitable for all environments. Care must be taken to protect these systems from physical damage, excessive heat, and corrosive substances to ensure optimal performance and longevity.

In NEC 2023, two new sections, 371.10 and 371.12, were introduced to outline the permitted and non-permitted uses of Flexible Bus Systems, respectively. Section 371.10 permits the utilization of FBS systems in various indoor and outdoor scenarios where space constraints may exist. These include service, feeders, and branch circuits, as well as exposed installations, setups in harsh environments (such as corrosive, wet, or damp locations), configurations behind access panels, and installations through walls and floors. Conversely, Section 371.12 prohibits the use of FBS in classified hazardous locations, hoist-ways, air-handling spaces, and areas prone to severe physical damage. The inclusion of these sections ensures that FBS systems are utilized exclusively in permitted applications, thereby mitigating the risk of damage to both the bus system and the connected power infrastructure.

What’s New for the 2023 NEC?

The table below presents a comparison between the 2020 NEC and the 2023 NEC regarding Sections 371.10 and 371.12.