Bus duct

5000 ampere copper and 4000A aluminium bus ducts
Bus duct inside an electrical service building at a Canadian oil refinery.
Bus duct inside an electrical closet in Mississauga Civic Centre, firestopped along with electrical conduit using firestop mortar.
1992 Bus duct segment with internal factory firestop that was replaced prior to fire testing with firestop mortar. To supply such systems, the bus duct manufacturer had to know where the duct penetrated fire separations required to have a fire-resistance rating.

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.

Construction

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.

Use and application

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.

Through-penetration firestopping

Bus ducts are building service penetrants that are required to be externally firestopped where they penetrate fire separations required to have a fire-resistance rating. Any internal firestops that are supplied by the manufacturer may be tested as integral components to either UL857 or IEEE C37.23 for North American models, and then via ASTM E814, UL1479 or ULC-S115. Bus duct-internal firestops mitigate the transmission of internal fires, smoke and heat between fire compartments through the combustion of bus duct-internal covalent wrappings, spacers and brackets.

See also

References

Wikimedia Commons has media related to Bus ducts.
Wikimedia Commons has media related to Bus duct fire testing.
Wikimedia Commons has media related to Bus duct fire test UL system C-BJ-8028.
This article is issued from Wikipedia - version of the Friday, October 16, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.