Noninsulated busbars shall have a minimum space of ___ in. between the bottom of a switchboard enclosure and busbars or other obstructions.
See answer and applicable Code reference
The correct answer is: c) 10
Article 408 covers switchboards and panelboards. The clearance requirements for conductor entering bus enclosures can be found in Sec. 408.5. As noted in Table 408.5, noninsulated busbars shall maintain a minimum 10 in. spacing between the bottom of the enclosure and busbars, their supports, and other obstructions.