Service entrance cables not installed underground and exposed to physical damage must be protected by which of the following?

Service entrance cables that are not installed underground and are exposed to potential physical damage must be adequately protected to ensure safety and compliance with the National Electrical Code. Rigid metal conduit provides strong protection against physical damage due to its durability and robustness.

Using rigid metal conduit safeguards the integrity of the cables by offering a sturdy barrier that can withstand impact and intrusion, ensuring that the wiring remains intact and operational. The provisions in the NEC require such protective means when cables are placed in locations where they may be subject to handling or other physical risks.

While flexible nonmetallic conduit and liquidtight flexible conduit can also provide protection, they are more commonly used in situations where there is movement or flexibility required in the installation, rather than in fixed, exposed locations. Rigid metal conduit is explicitly recognized in the NEC for its protective qualities under these circumstances, making it the most appropriate choice for protecting service entrance cables exposed to physical damage.