What must be done if a circuit conductor is connected to a source with higher available maximum current?

When a circuit conductor is connected to a source that has a higher available maximum current, it is essential to implement overcurrent protection at the connection point. This is crucial to prevent the conductors from carrying more current than they are designed to handle, which could lead to overheating, potential equipment damage, or even fire hazards.

Overcurrent protection devices, such as circuit breakers or fuses, are designed to disconnect the circuit when the current exceeds a predetermined safe level. By ensuring that these protective devices are properly sized and installed, the risk associated with connecting to a higher maximum current source is significantly mitigated. This is a fundamental safety requirement as outlined by the National Electrical Code (NEC), emphasizing the importance of protecting conductors from overload conditions.

The other options suggest practices that do not effectively address the potential hazards associated with connecting to higher current sources. For instance, isolating the circuit from high current sources might not always be feasible or practical. Using lower ampacity conductors could lead to insufficient capacity to handle the load, while obtaining a special exemption from the NEC does not address the inherent safety needs of the installation. Therefore, implementing overcurrent protection is the most effective and compliant approach in this scenario.