All receptacles installed on 15- and 20-ampere branch circuits must be of which type?

Receptacles installed on 15- and 20-ampere branch circuits must be of the grounding type because grounding is essential for safety in electrical systems. Grounding provides a path for electrical current to safely dissipate into the earth in the event of a fault or short circuit. This reduces the risk of electric shock to users and prevents equipment damage.

Grounding-type receptacles are designed to accept three-prong plugs, which include a ground pin that connects to the grounding system of the electrical installation. This is especially critical in damp or potentially hazardous locations where the risk of electric shock is higher.

In contrast, other receptacle types, such as non-grounding type, do not provide this level of safety. Weather-resistant receptacles are designed for outdoor use but do not inherently provide the necessary grounding. GFCI (Ground Fault Circuit Interrupter) receptacles, while offering protection against ground faults, are not a requirement for every branch circuit but rather used in specific locations. Thus, the grounding type is the standard for all receptacles on the specified circuits to ensure a safe electrical environment.