An electrical junction box is simply an enclosed space that is used to house electrical wires and connections safely from the surroundings and to protect anything that could come in contact with it. These often form parts of the wiring system in residential or commercial buildings and maybe put up underneath the floor or inside concrete casings with just the opening being visible.
Types of Electrical Junction Boxes
- Electrical Junction Boxes at Home
There are many kinds of electrical junction boxes available in the market of which the most common are the ones used in the electrical wiring systems of houses. These are available in hardware stores for DIYers and is used for ceiling fans and heavy light fixtures.
- Metal and Plastic Junction Boxes
When using a metal conduit for the wiring, a metal junction box may be necessary. This box and the conduit, together, can be used as grounding. If a non-metallic sheath cable is used then either a plastic junction box or a metallic one could be used.
- Round Pan Junction Box
These are typically ½ or ¾ inches deep and are used for lighting fixtures that are either for the ceiling or to be mounted on a wall. The mounted fixtures should not be too heavy in this case. If it is specially rated, then some of these junction boxes may also be used for ceiling fans.
- Octagon and Round Junction Boxes
These typically have a depth of about 1-½ to 2-⅛ inches. It is commonly used for heavier light fixtures, meant to be ceiling or wall-mounted, they can be secured easily to a drywall without needing to drill a large hole.
- Ceiling Fan Junction Box
These junction boxes are specifically rated for ceiling fans and come in different shapes and sizes. Only junction boxes that are rated for ceiling fans should be used as the fan needs special fixtures due to the dynamic force of the rotating blades that it must bear while working.
- 4-inch Square Box
Square junction boxes have a standard depth of 1-½ to 2-⅛ inches but have additional inner space due to their shape. Since it has more space, the 4-inch boxes are also used to run multiple sets of conductors in one or more directions. They can also be used for lighting fixtures that are ceiling or wall-mounted.
More about Junction Boxes
Most electrical junction boxes are constructed out of a 4-inch square electrical box. Junction boxes are installed so that they are easily accessible. It may contain separate panels for different set of wirings, depending upon the requirements. It should never be installed where it is kept concealed and should always have a cover that has no openings.
The box covers come in a variety of shapes and sizes to fit the different kinds of junction boxes. An uncovered box is a big hazard and usually illegal, depending upon the electrical codes in a locality. Junction boxes are usually covered with a safe square, no-hole box cover. Sometimes, the covers may have holes to accommodate the receptacles and switches in the junction box.
If there is a need to extend the capacity of an electrical junction box, then a box extender will have to be used. These come in standard sizes and shapes, similar to the junction boxes except that they do not have any front or back covering. The can be easily fixed on to the front part of the junction boxes to extend the capacity.
For outdoor junction boxes, the covers will have to be weatherproof.