Electrical junction boxes are devices that contain the wiring junctions or intersections that allow the wiring in the home or public building to interface with the main power supply provided by a local utility. The presence of the box is generally regarded as both practical and more esthetically pleasing than a bunch of exposed electrical wires. While the exact configuration for electrical junctions containers of this type vary slightly, there are a few basic elements that are common to all designs.
For many people, the main purpose of a junction box is to conceal the electrical junctions from sight. Usually constructed with the use of metal or hard plastic, the general appearance of the box is either a square or rectangular design. A door on the front allows access to the interior. The door may be recessed in the front of the junction box, or the entire facing may swing upward or downward to allow access to the junctions within the device. In many homes, the box proper is recessed into a wall, with only the front panel open to view. This makes it very easy to hang a piece of art over it and hide it completely from view.
While it is true that the junction box presents a neater means of concealing electrical junctions, the real value of the box is providing a degree of protection for the wiring interface at various junction points. It can also help contain sparks in the event that one of the junctions overloads for some reason, and thus limit the amount of damage that is caused. The typical device today usually includes a safety switch that allows the connections made within the box to be shut down in an emergency.
The life of a typical electrical junction box can be measured in decades. Occasionally, upgrades to the wiring within the building will dictate the installation of a larger box to accommodate additional electrical junctions or larger electrical cables. However, if the original wiring remains in good condition and there is no added burden placed on the overall electrical system within the building, it does not usually have to be replaced.