Feeder Busway
A feeder busway is a prefabricated electrical distribution system consisting of bus bars in a protective enclosure, designed to conduct bulk electric power from a source (e.g., service entrance or switchboard) to a center of distribution. It has no plug-in openings along its length, though it may allow bolt-on devices. In Canada and the U.S., it complies with CSA C22.2 No. 27 / UL 857 and the Canadian Electrical Code (CEC) / NFPA 70 NEC, rated up to 1000 V and 6000 A.
On a manufacturing shop floor, feeder busway is used for high-ampacity, compact power distribution from utility transformers to main disconnects, switchboards, motor control centers (MCCs), or large process loads like welding lines and HVAC units. It offers modular, sectionalized construction for easier rerouting and expansion compared to conduit and wire, reducing voltage drop with solid busbars. Installation requires secure supports at intervals of 1.5 m (5 ft) or less, and the busway must be suitable for the environment (e.g., outdoor, wet, or corrosive locations require listed types). Overcurrent protection must not exceed the busway's ampacity, and fire barriers are needed at wall or floor penetrations. Grounding and vapor seals at building walls are essential for safety and code compliance.
Under CSA C22.2 No. 27 and NEC, what differentiates feeder busway from plug-in busway in terms of design and permitted use?
Feeder busway has no plug-in openings and is intended to conduct power from sources to distribution centers, with possible bolt-on devices. Plug-in busway includes plug-in openings for branch loads, requiring listed plug-in units with overcurrent protection and externally operable disconnects. Feeder busway has fewer worker-accessible energized interfaces, reducing lockout complexity.
How does the standards update (UL 857 / CSA C22.2 No. 27) to 1000 V impact design and risk management for feeder busway in industrial plants?
The update increases maximum voltage from 600 V to 1000 V, requiring greater attention to clearance, creepage distances, insulation, and joint design. It demands updated arc flash hazard analyses and PPE, and power system owners must reflect higher voltages in assurance in writing documentation and worker training for switching and lockout.
What are the key code requirements for overcurrent protection when feeder busway is used as a feeder or service entrance conductor?
The busway must be protected by an overcurrent device not exceeding its allowable current rating. For feeder or branch circuits tapped off, devices must contain required overcurrent protection. For service entrance use, the busway listing must allow it, and the main disconnect must comply with service-entrance rules.