How long must rod and pipe electrodes be at a minimum?

The minimum length required for rod and pipe electrodes is established to ensure effective grounding and bonding in electrical systems. According to the National Electrical Code (NEC), rod and pipe electrodes must be at least 8 feet long, which allows a substantial portion of the electrode to be buried in the ground, providing a reliable electrical connection with the earth. This grounding is critical for safety, as it helps to prevent electrical shock and allows overcurrent protection devices to function effectively by providing a path for fault currents.

The correct answer is 8 feet because this specification is based on the need for adequate grounding under various soil conditions, which can affect the resistance to ground. Longer electrodes may provide better grounding in some scenarios, but the NEC mandates that a minimum length of 8 feet be used for rod and pipe electrodes as a baseline for safety and effectiveness in grounding practices.