An electrical junction box (also known as a "jbox") is an enclosure housing electrical connections. Junction boxes protect the electrical connections from the

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...

, as well as protecting people from accidental

electric shocks Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce ...

Construction

A small metal or plastic junction box may form part of an electrical conduit or

thermoplastic-sheathed cable A thermoplastic-sheathed cable (TPS) consists of a toughened outer sheath of polyvinyl chloride (PVC) thermoplastic, covering one or more individual annealed copper conductors, themselves insulated with PVC. This type of wiring is commonly used ...

(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 in the gallery) may be buried in the

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

of a wall (although full concealment is no longer allowed by modern codes and standards) or cast into

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

—with only the cover visible. It sometimes includes built-in 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 A pattress or pattress box or fitting box (in the United States and Canada, electrical wall switch box, electrical wall outlet box, electrical ceiling box, switch box, outlet box, electrical box, etc.) is the container for the space behind electric ...

. The term junction box may also be used for a larger item, such as a piece of

street furniture Street furniture is a collective term for objects and pieces of equipment installed along streets and roads for various purposes. It includes benches, traffic barriers, bollards, post boxes, phone boxes, streetlamps, traffic lights, traf ...

. In the UK, such items are often called a cabinet. See

Enclosure (electrical) An electrical enclosure is a cabinet for electrical or electronic equipment to mount switches, knobs and displays and to prevent electrical shock to equipment users and protect the contents from the environment. The enclosure is the only par ...

. Junction boxes form an integral part of a circuit protection system where

circuit integrity Circuit integrity is how little can a fire affect an electrical circuit's operation. It is a form of fire-resistance rating. Circuit integrity is achieved via passive fire protection means, which are subject to listing and approval use and co ...

has to be provided, as for emergency lighting or emergency power lines, or the wiring between a

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...

and a

control room A control room or operations room is a central space where a large physical facility or physically dispersed service can be monitored and controlled. It is often part of a larger command center. Overview A control room's purpose is produc ...

. In such an installation, the

fireproofing Fireproofing is rendering something (structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a ...

around the incoming or outgoing cables must also be extended to cover the junction box to prevent

short circuit A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circui ...

s inside the box during an accidental fire. Image:Junction box.jpg, Electrical junction box in the process of installation. Electrical conduits terminate at the sides and cables pass through or are joined inside the box. File:Junction box2.jpg, A metal junction box File:Australian Internal Surface Mounted Junction Box.jpg, Australian Internal Surface Mounted Junction Box—showing wiring stages.

Solar panel

A PV junction box is attached to the back of the solar panel and it is its output interface.

References

External links

{{Commons category , Junction boxes
NEMA: National Electrical Manufacturers Association

IBEW: International Brotherhood of Electrical Workers

NECA: National Electrical Contractors Association
Cables Electrical wiring

Construction

Solar panel

See also

References

External links