In an older home with a subpanel wired with non-metallic sheathed cable, how should the ground wire be configured?

In an older home where a subpanel is wired with non-metallic sheathed cable, the ground wire should indeed be configured by being connected to a separate grounded bus bar. This configuration helps ensure that the grounding system is effective and compliant with current electrical codes. A separate ground bus bar allows for proper grounding that is isolated from the neutral, which is critical for preventing potential hazards such as electrical shock or fire.

Keeping the ground and neutral separated in subpanels is essential because it minimizes the risk of return current flowing through the ground system, which can occur if the neutral and ground are bonded together in a subpanel. This separation ensures that the proper path for fault current remains intact, which promotes safety and the effectiveness of the circuit breakers in the event of a fault.

The other configurations would compromise safety standards; for instance, connecting the ground to a separate ground rod might not provide an adequate ground reference for the subpanel, while bonding the ground to the panel cover screws does not establish a reliable ground path. Connecting to the neutral bus bar is also against modern codes, as it increases the likelihood of neutral return current on the ground wire, leading to dangerous situations.