Usual Electrical Boxes

Electrical boxes are necessary components of your home electrical system that encase wire connections to protect them from potential electrical dangers. But for many DIYers, the wide variety of boxes is bewildering. There are different types of boxes include metal boxes and plastic boxes, “new work” and “old work” boxes; round, square, octagonal boxes and more.

You could buy all of the most commonly used boxes for home wiring projects at home centers or large hardware stores, of course it’s important to know the differences in order to buy the correct box for definite use.

Here, we will introduce several main electrical boxes.

1. Metal and Plastic Electrical Boxes

Most of electrical boxes are made of metal or plastic: Metal boxes are generally made of steel, while plastic boxes are either PVC or fiberglass. Weatherproof metal boxes for outdoor applications are usually made of aluminum.

It is recommended to use a metal box if you are using metal conduit to run wiring to the electrical box—both to anchor the conduit and because the conduit and metal box itself may be used to ground the system. Generally speaking, metal boxes are more durable, fireproof, and secure.

Plastic boxes are pretty cheaper than metal boxes and usually include built-in clamps for wires. When you are using a non-metallic cable, such as Type NM-B (non-metallic sheathed cable), then you can use either plastic boxes or metal boxes as you wish, as long as the cable is secured to the box with an appropriate cable clamp. Modern wiring systems with NM-B cable usually include a ground wire inside the cable, so the box is not part of the grounding system.

2. Standard Rectangular Boxes

Standard rectangular boxes are known as “single-gang” or “one-gang” boxes, they are typically used for carrying single light fixture switches and outlet receptacles. Their dimensions are about 2 x 4 inches in size, with depths ranging from 1 1/2 inches to 3 1/2 inches. Some forms are gangable—with detachable sides that are removeable so the boxes can be linked together to form a larger box for holding two, three, or more devices side by side.

Standard rectangular boxes come in various types of “new work” and “old work” designs, and they can be metallic or non-metallic (with metallic being more durable). Some types have built-in cable clamps for securing NM cables. These boxes are selling at different prices, but most standard options are obviously affordable.

3. 2-Gang, 3-Gang, and 4-Gang Boxes

Like standard rectangular boxes, gangable electrical boxes are used for holding household switches and electrical receptacles, but they are oversized so that two, three, or four devices can be mounted side-by-side all together.  Like other boxes, these come in a variety of “new work” and “old work” designs, some with built-in cable clamps.

The same construction can be created by using standard rectangular boxes with a gangable design that allows the sides to be removed so the boxes can be joined together to form larger boxes. Gangable electrical boxes are most often made of extremely durable galvanized steel, however, you can find some plastic snap-together options at certain hardware stores (sometimes for a slightly higher price).