What condition must the main switchboard busing fulfill?

The main switchboard busing must conduct full load current continuously to ensure safe and efficient operation of the electrical system. This requirement is essential because the busing serves as the pathway for electrical current to flow through the switchboard from one point to another, including from the feeders to the various branch circuits.

By being designed to handle the full load current, the busing ensures that it can accommodate the maximum expected current without overheating or failing. Proper current-carrying capacity is critical for maintaining operational reliability and preventing electrical malfunctions or hazards that could arise from under-designed components.

While options like being removable, insulated, or replaceable might also be relevant characteristics in some contexts, they do not directly address the fundamental requirement for the busing to safely conduct the necessary current levels for the system to function effectively.