Electrical-boxes and junction boxes

Electrical-boxes, Junction Boxes, Fixture Boxes, Receptacle Boxes

Box Fill: How many wires you can put in a box? The NEC Code requires wiring to be protected and enclosed when devices such as receptacles, fixtures and switches are being installed. Sometimes it is necessary to junction or splice wires. When splicing wires, an accessible electrical junction box box is necessary to enclose the spliced wires. This list shows various electrical boxes and displays the box name and describes the typical application.

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The most common type of materials that electrical-boxes are made of are: Plastic, Fiberglass, Steel, Aluminum and Bakealight. The metal boxes come with knock-outs for using conduit such as EMT (electrical metallic tubing) or Flex - steel or aluminum.Why don't you see the exact same electrical-box at your supplier? The availability of the types of boxes will depend upon which electrical manufacturer or purchasing channel your supplier has a contract with.

Boxes and Wire-Fill How many wires can be installed into an electrical box will depend on how many Cubic Inches the box has and what size wires are being installed. Below is a chart of a few common electrical junction-boxes and the actual information which should be stamped or molded into each enclosure. A good rule of thumb is to never over fill a box, leave yourself plenty of room, and don't cut your wire too short either - you can always trim off a little, but you can't stretch it. Keep in mind that the Ground Wires are not counted.

ELECTRICAL BOX EXAMPLES	Box CU. IN.	#14 Wires	#12 Wires	#10 Wires
3-INCH PANCAKE METAL	4.5	2	2	0
3-INCH CUT-IN FIBERGLASS	14.0	7	6	5
1-GANG CUT-IN FIBERGLASS	16.0	8	7	6
1-GANG CUT-IN FIBERGLASS	18.0	9	8	7
1-GANG NAIL PLASTIC	20.5	10	9	8
2-GANG CUT-IN FIBERGLASS	28.0	14	12	11
2-GLASS FACE NAIL PLASTIC	32.0	16	14	12
3-GANG CUT-IN FIBERGLASS	42.5	21	18	17
2-GANG NAIL PLASTIC	43.5	21	19	17

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Lets take a look at some common electrical junction boxes and their uses: