Busway has many advantages over a conductor-and-raceway system. One advantage is the large cross-sectional area, which means much lower circuit impedance, leading to better performance and longer lifespan. Due to how it’s connected together, busway is relatively simple to install, change, and add onto. Lifetime cost is lower than with the raceway-and-conductor method.
You can install it through walls and through floors [368.10]. If it is of totally enclosed, nonventilating construction, you can even run it behind access panels (but you have to make the joints between sections and fittings accessible for maintenance).
So why isn’t busway used for all service, feeder, and branch circuits? Several reasons:
- It can’t be subject to severe physical damage [368.12]. One solution could be to install it as a backbone along the ceiling or up in the rafter structure, where it is protected. But you would then need to get through the dangerous area with tubing or conduit suited to the hazards.
- It can’t be subjected to corrosive vapors. The typical solution is to use a raceway that is made from a corrosion-resistant material (e.g., rigid PVC conduit, Article 352) or PVC-coated rigid metallic conduit (often seen in applications such as refineries).
- You can’t install it in hazardous locations or wet locations because of its “open” construction [368.12(C) and (D)].
- You can’t install it in hoistways or less than 8 ft above the floor of a working platform [368.12(B) and (E)]. You can break the working platform rule if the particular busway you are using is provided with an identified cover.
The decision on which wiring method is optimal for a given application in a given environment under specific conditions of use is can be difficult to get right. The factors just mentioned may also have to be balanced against cost, time, aesthetics, future uses, craft skill at installation, maintenance concerns, efficiency, circuit density in the run(s), and materials availability. Busway often comes out ahead in this calculus, but only for applications for which it is not prohibited by 368.10.
