PROJECTS ONLINE: CHOOSING A METALLIC ELECTRICAL BOX
Project Difficulty:
Moderate
Metallic electrical boxes are sturdier than nonmetallic ones and are preferred or required in certain situations.
1.
When to Choose a Metallic Electrical Box
You should choose a metallic box if:
a) You are going to run metal conduit (a protective casing for carrying insulated wires). Typical applications are exposed wiring in a garage or shop. It's usual to run common NM cable across the overhead joists or high around the walls in inaccessible areas, and then run the cable in thinwall conduit down the walls and into a metal box.
b) The boxes will be exposed on a wall surface. Such locations are called high abuse because, being exposed, they can be hit by lumber, tools, etc.
c) You need a variety of box designs for your system. Metallic boxes have been around longer than nonmetallic, so there are a wider variety of designs (they may not be easy to find, however).
d) You are placing the boxes in concrete. This is also a high-abuse area--nonmetallic boxes may not hold up.
e) Grounding is an issue. If the box and surrounding metal conduit are grounded, damaging voltages from lightning strikes or line surges can be minimized and redirected to flow to the ground.
