Busway Fundamentals – How Overhead Plug-In Power Works
Busway systems are used to distribute electrical power overhead in commercial and industrial environments. This guide explains the fundamentals of busway, the major types used in industry, and how modern open-slot track busway fits into today’s electrical layouts.
Major Types of Busway Systems Used in Commercial and Industrial Design
While several forms of busway exist, most were originally designed for fixed layouts, limited access, or high-amperage backbone distribution. As facilities have become more modular and reconfigurable, open-slot track busway has emerged as the preferred modern solution for flexible overhead power distribution.
Across the industry, busway appears in several forms. Each type is optimized for different electrical needs, from carrying large amounts of power through a building to allowing plug-in access along work areas. The sections below explain the four major categories engineers encounter in commercial and industrial design.
Trolley Busway
Sliding Trolley Systems
Trolley busway systems distribute power using a sliding trolley mechanism that repositions power drops along straight runs. While effective for tool rails and linear work areas, trolley systems are limited to single-row layouts and do not support interconnected or grid-based designs common in modern facilities.
While trolley busway enables sliding drops along straight runs, open-slot track busway eliminates single-row limitations by allowing continuous plug-in access in multi-directional layouts.
Feeder Busway
High-Amperage Busduct
Feeder busway (often referred to as “bus duct”) consists of enclosed busbars designed to carry large amounts of power between major electrical equipment such as switchgear, risers, PDUs, or RPPs. Its role is backbone distribution — not flexible power access.
Track Busway does not manufacture high-amperage feeder bus duct. Instead, open-slot track busway is typically deployed downstream of feeder systems to distribute power where frequent changes, modular layouts, and plug-in access are required.
Legacy Plug-In Busway
Fixed-Window Systems
Legacy plug-in busway uses fixed rectangular tap windows spaced at predetermined intervals. Plug-in units must align exactly with these factory-cut openings, which limits device placement and reduces flexibility. While still used in older installations, fixed-window systems are poorly suited for environments that change over time.
Fixed-window plug-in busway represents an earlier generation of distribution; open-slot track busway replaces these limitations with continuous access along the entire run.
Open-Slot Track Busway
Modern Plug-In System
Open-slot track busway is the modern evolution of plug-in distribution. Instead of fixed tap windows, the system provides continuous access along the entire length. Devices can be added or repositioned anywhere without tools, rewiring, or downtime. Because of its scalability, safety compliance, and fast installation, open-slot busway is widely used today in industrial, lab, R&D, manufacturing, and commercial environments.
Traditional busway systems were designed for static electrical layouts. Open-slot track busway was designed for change. By providing continuous plug-in access along the entire run, Track Busway supports modern industrial, lab, automation, and commercial environments where power needs and equipment layouts evolve over time.
A modern open-slot architecture that allows plug-ins almost anywhere along the run. Ideal for flexible layouts, industrial work cells, labs, automation, and R&D spaces where equipment moves frequently.
This diagram shows how a run is built — only a few modular components are required for plug-and-play overhead power. Click any thumbnail to view the product.
This diagram shows how a run is built — only a few modular components are required for plug-and-play overhead power. Click any thumbnail to view the product.
- Faster installation — significantly reduces field labor and wiring
- Modular and pre-engineered — supports phased builds and future changes
- Compact overhead distribution — less space than conduit and cable trays
- Safer by design — enclosed conductors and UL-classified systems
- Lower lifecycle cost — simpler modifications and long-term adaptability
Busway is a power distribution system defined by UL 857 that uses enclosed conductors to deliver electricity along a continuous run. Unlike traditional pipe-and-wire systems, busway is factory-assembled, modular, and designed to scale with a facility over time.
Modern busway systems range from high-amperage feeder busduct to plug-in busway and open-slot track busway — each serving a specific role in a facility’s electrical infrastructure.
Because busway is modular and pre-engineered, it allows facilities to expand, reconfigure, or add loads over time without rebuilding their electrical infrastructure.
Busbar – a conductor used inside equipment or enclosures (panels, switchgear)
Bus duct (feeder busway) – enclosed high-ampacity busbar assemblies used for backbone power distribution
Busway – the broader UL 857 / NEC-defined category that includes feeder, plug-in, trolley, and track systems
Open-slot track busway – the modern evolution of busway, providing continuous plug-in access along the run for flexible power, lighting, and data
Busway is a modular electrical distribution system that uses enclosed or open conductors to deliver power throughout a facility. Instead of cutting and bending conduit every time a circuit is added or moved, busway provides a reusable overhead “spine” where power can be tapped along rows, grids, or full building spans.
Overhead busway carries power through insulated busbars inside a protective housing. Plug-in units or PowerDrops connect to those busbars along the run, so circuits can be added or relocated without pulling new wire or installing new junction boxes. This makes layout changes much faster than traditional pipe-and-wire installations.
In practice, engineers typically encounter four categories of busway: high-ampacity feeder bus duct for backbone distribution, trolley busway for sliding drops along a straight run, fixed-window legacy plug-in busway with pre-cut tap locations, and modern open-slot track busway that provides continuous plug-in access along the length.
“Bus duct” usually refers to high-ampacity feeder busway used between switchgear, PDUs, risers, or large equipment.
Busway is the broader family that includes feeder bus duct, plug-in busway, trolley systems, and open-slot track busway.
All are busway, but not all busway is high-amp feeder bus duct.
Traditional conduit requires cutting, threading, pulling wire, and making permanent splices in junction boxes every time alayout changes. Busway eliminates most of that work by providing a modular overhead channel where power can be added, moved,or extended without rewiring. As facilities adopt more automation and reconfigurable production lines, busway has become apreferred method for flexible overhead power distribution.
No. In electrical engineering, busway refers to a prefabricated power distribution system defined by UL 857 and the National Electrical Code. Transportation “busways” refer to dedicated roadways for transit vehicles and are unrelated to electrical power distribution.
