Illustration: The Spruce / Joshua Seong
Electrical boxes encase wire connections to protect them from short circuits.
This guide breaks down the different types of electrical boxes to safely install electrical devices around your home.
If you need help installing the box, call a professional.
Illustration: The Spruce / Joshua Seong
Other types of boxes can be used as junction boxes.
Tip
Install junction boxeswhere they are always accessible.
Junction boxes must also be covered with solid covers.
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New Work Electrical Box
A new work electrical box is installed in an open wall.
The box is nailed or screwed to the side of the wall studs.
It is secure and strong.
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Standard rectangular boxes can be metallic or non-metallic.
Some types have built-in cable clamps forsecuring NM cables.
What Is Gang or Gangable?
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With electrical components, gang or gangable means that the pieces are capable of being joined.
Still, they are oversized so that two, three, or four devices can be mounted side-by-side.
Gangable electrical boxes are often made of durable galvanized steel.
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These can be only 1/2-inch or 3/4-inch deep and made of plastic or durable metal.
The number of wires in the electrical box should never exceed its safe fill capacity.
These boxes range from 1-1/2 to 3 inches deep.
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They provide much more room for wiring than shallow round pan boxes and can be used as junction boxes.
These boxes come in several types and sizes, including 1/2-inch-deep versions and standard 2-1/8-inch-deep boxes.
Ceiling fan boxes are usually round but can be octagonal and are either made of metal or durable plastic.
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Ceiling fan boxes must be UL-listed for ceiling fan mounting and marked For Use With Ceiling Fans.
Do notuse standard round or octagonal boxes for installing ceiling fans.
Ceiling fan boxes require special fastening to withstand the dynamic loading of a rotating fan.
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For this reason, 4-inch square boxes often are used to run several conductors in two or more directions.
Solid or blank covers have no holes and are used with junction boxes or for enclosing unused boxes.
Covers for 4-inch square boxes may have special cutouts to accommodate switches or receptacles (outlets).
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They are used for installing outdoor receptacles (outlets) and light fixtures.
Box extenders are shaped like the boxes they are intended for but without a back panel.
Metal or plastic extenders should be used to match the material of your electrical box.
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Metal vs.
Plastic Electrical Boxes
Most electrical boxes are either metal or plastic.
Metal boxes are generally steel, while plastic boxes are PVC or fiberglass.
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Metal Electrical Boxes
Metal electrical boxes are best for metal-sheathed cable or metal conduit.
Weatherproof metal boxes for outdoor use are generally made of aluminum.
Plastic Electrical Boxes
Plastic electrical boxesare best for Romex or non-metallic cables.
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Choosing an Electrical Box
Choose an electrical box based on its intended purpose.
Consider the key in of electrical cable you are using, too.
If you are installing wires enclosed in metal conduit, you must use a metal box.
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Also, determine whether you need an old work or new work electrical box.
An outlet box and a junction box can be the same thing.
The pop in 2 junction box is only for indoor use.
The bang out 1 junction box protects against water and other liquids, so it can be used outdoors.
In a broad sense, any electrical box can be used as a junction box.
Most standard code-approved electrical boxes found at home centers can be used as junction boxes.
314.25 Covers and Canopies.
National Electrical Code (NEC).
