Electrical Junction Boxes

An Electrical Junction Box is used for Containing Electrical Wires and are Commonly Hidden behind Finished Walls

By Mark J. Donovan

Electrical junction boxes are used for containing electrical wire connections. They are typically used to split or join wire runs that feed power to electrical devices. Electrical junction boxes are often positioned behind finished walls in indoor residential applications. In some cases, such as in concrete walls, they are cast into the concrete so that only their access door is exposed.

In other cases they are installed as part of an electrical conduit system where the conduit and the electrical boxes are not buried, but attached to the surface of the interior walls. Sometimes you see this in industrial or commercial applications.

Electrical junction boxes are available as metal enclosures or non-metallic enclosures. Metal enclosures need to be properly grounded and are usually more expensive than non-metallic electrical enclosures.

Junction boxes are also sold in a variety of shapes and sizes, including square, rectangular and circular. It is important to select an electrical junction box of the right size and shape, and that will properly fit the number of electrical wires and connections required. Squeezing too many wires or electrical connections in too small of an electrical junction box could lead to broken wires or short circuits.

Electrical junction boxes are also sold in a variety of application rating types. The National Electrical Manufacturers Association (NEMA) has a rating system for electrical junction boxes to identify which type of electrical enclosure to use in a particular type of application. For example, a NEMA 1 rated electrical junction box is meant for protecting electrical connections from objects and personnel. It is not dirt, dust, oil, or water resistant.

NEMA 3R electrical enclosures are typically meant for outdoor applications. They are meant to protect electrical connections from falling rain, snow, sleet and ice formation, but they do not include a sealing gasket.

NEMA 3S electrical junction boxes are also meant for outdoor applications and to protect against wind driven weather conditions and dust. There are a number of other electrical junction boxes with other NEMA ratings, so it is important when selecting one you pick the right one for your particular application.

So if you are performing some residential electrical wiring, and need to splice or join electrical wires outside the main electrical circuit panel, make sure to use an electrical junction box. The National Electrical Code requires it, and you and your home will be safer for doing so.

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