Which conductor of all 3-wire, DC systems supplying premises wiring shall be grounded?

In a 3-wire direct current (DC) system that supplies premises wiring, the neutral conductor is the one that must be grounded. The neutral acts as the return path for electric current and is intended to complete the electrical circuit by returning the current back to the source after it has passed through the load (such as appliances or lighting). Grounding the neutral conductor ensures that, in the event of a fault or short circuit, the excess current can safely dissipate into the ground, which helps to protect both people and equipment from electrical hazards like shocks or fires.

By grounding the neutral, we also help to stabilize the voltage levels in the system. This grounding provides a reference point for the electrical system, ensuring consistent operation and reducing the risk of stray voltages that can occur due to faults.

In contrast, the hot conductor usually carries the current from the power source to the load and is not grounded, as doing so would expose it to potential safety risks. The ground conductor, while important for overall safety, serves to provide a path to ground for fault currents and does not typically carry current in normal operation, thus it is not the conductor that is grounded in the context of this question. The term "common" is not typically used in this context and