If a branch-circuit rated fuse does not have an interrupting rating marked, what is its default rating?

When a branch-circuit rated fuse does not have an interrupting rating marked, it defaults to an interrupting rating of 10,000 amperes. This is a standard practice established by electrical codes and standards to ensure a minimum level of protection and reliability in electrical systems.

The 10,000A rating allows for adequate protection against potential fault currents that could occur in many residential and commercial electrical applications. It serves to ensure that if a fault occurs, the fuse can safely interrupt the circuit without posing a risk to people or equipment.

The other ratings do not reflect the default for unmarked fuses according to established electrical standards. Therefore, the choice of 10,000A as the default interrupting rating is both a safety measure and a regulatory guideline that electricians and engineers must adhere to when working with branch-circuit rated fuses.