Bus Ducts

In electrical power distribution, a bus duct (also called busway), is a sheet metal duct containing either copper or aluminium busbars for the purpose of conducting a substantial current of electricity. It is an alternative means of conducting electricity to power cables or cable bus.

Section of copper bus duct with sandwiched bus bars

Section of aluminium bus duct with sandwiched bus bars

Innards of bus duct showing plastic wrappings of sandwiched busbars and hollow plastic tube spacers.

Individual busbar wrapping

Similar to cable tray, bus ducts have thicker, cold-formed steel side rails and thinner sheet metal coverings. Busbars inside may be separated with distinct and even gaps between them, or “sandwiched” together.

Typically, individual busbars are wrapped or coated with a non-conducting, covalent material, such as plastic or (in older systems) electrical tape.

At the connection point, busbars flare out to enable connection to the next segment.

Bus ducts are used in commercial and industrial settings, both indoors and outdoors. Manufacturers deliver them assembled in large segments for electrical contractors to connect and support.

Firestop test sample including 2 bus ducts

ASTM E814 test sample after external firestop mortar installation

ASTM E814 test sample after external firestop insulation installation

Bus duct firestop test, furnace view

End of bus duct on unexposed side of firestop test sample, as smoke generation begins

...
Wikipedia