According to NEC section 406.3(A), which branch circuits are required to have grounded receptacles?

Grounded receptacles are required on 15A and 20A branch circuits according to NEC section 406.3(A) because these circuits are commonly used in residential and commercial settings for general-purpose outlets. The requirement for grounded receptacles is primarily for safety purposes, as it helps to prevent electrical shock and ensures that any stray voltage can be safely conducted to ground rather than presenting a hazard to users.

Using grounded receptacles on these circuits allows for the safe connection of portable appliances and tools that may potentially have a fault condition. By ensuring that all 15A and 20A circuits are equipped with grounded receptacles, the National Electrical Code aims to enhance safety and protect both the electrical infrastructure and the users.

In contrast, branch circuits such as 5A, 10A, 30A, and 40A may have different requirements or are designed for specific appliances that can operate safely without grounded receptacles or may not be used for general-purpose applications where receptacles are frequently accessed, thus not requiring the same safety measures.