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
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
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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