What is the purpose of grounding metal faceplates when using nonmetallic boxes?

Grounding metal faceplates in conjunction with nonmetallic boxes primarily serves to protect against electrical shock. When metal faceplates are installed, they can potentially become energized if a fault occurs, such as a wire insulation failure or accidental contact with live wires. By grounding these faceplates, any unintended electrical current is directed safely to the ground, reducing the risk of an electric shock to individuals who may come into contact with the faceplates.

In addition to safety, grounding facilitates proper operation of electrical devices and enhances the overall safety of the electrical installation, ensuring that all exposed conductive parts are effectively connected to the earth. This grounding mechanism is crucial, especially in environments where moisture or physical contact with the faceplates may occur.