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 cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...

, as well as protecting people from accidental electric shocks.

Functions of the junction box

A small metal, plastic or fiberglass junction box may form part of an electrical conduit or thermoplastic-sheathed cable (TPS) wiring

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

in a building. If designed for surface mounting, it is used mostly in ceilings, concrete 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 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 aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...

—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. 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 bench (furniture), benches, traffic barriers, bollards, post boxes, phone boxes, streetlamps, traffic ...

. 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 A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

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 (Building, 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 u ...

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 circuit ...

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. File:Kuhlo-dosa med Wago.png, Swedish junction box in Kuhlo-style with lever-connector Wago 221, where ground and neutral are connected in common.

Solar panel

A PV junction box is attached to the back of the

solar panel A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...

and it is its output interface.

References

Back Junction Boxes

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

Functions of the junction box

Solar panel

See also

References

External links