Boxes
An electrical junction box is a container for electrical
connections, usually intended to conceal them from sight and deter tampering. A
small metal or plastic junction box may form part of an electrical conduit or thermoplastic-sheathed
cable (TPS) wiring system in a building. If designed for surface
mounting, it is used mostly in ceilings, under floors or concealed behind an
access panel - particularly in domestic or commercial buildings. An appropriate
type (such as that shown on the right) may be buried in the plaster of a wall (although full concealment
is no longer allowed by modern codes and standards) or cast into concrete -
with only the cover visible.
It
sometimes includes in-built terminals for the joining of wires.
A
similar, usually wall mounted, container used mainly to accommodate switches. Sockets
and the associated connecting wiring is called a Pattress The term junction box may also be used for a larger item,
such as a piece of street
furniture. In the UK, such items are often called a cabinet. See Enclosure (electrical).
Junction
boxes form an integral part of a circuit protection system where circuit integrity has to be provided, as for emergency
lighting or emergency power lines, or the wiring between a nuclear reactor and a control room. In such an installation,
the fireproofing around the incoming or outgoing cables
must also be extended to cover the junction box to prevent short circuits inside the box during an accidental
fire.