A 300-foot run of 800-amp busway is installed in a commercial warehouse building. The last 20' of the busway run is reduced to a bus rating of 200 amps. What is the requirement for installation of the smaller bus?

The requirement for the installation of the smaller bus, rated at 200 amps, within a larger system of 800 amps is that it must be protected by an overcurrent device. This is because the smaller busway section is at a higher risk of carrying an overload current that could exceed its ampacity, which would lead to overheating and potential damage.

Protecting the smaller 200-amp bus section with an overcurrent device ensures that in the event of an overload, the device will disconnect the circuit before the current exceeds the safe limit of the busway. This is essential for maintaining the safety of the electrical system and preventing electrical fires or equipment damage.

The other options do not align with accepted electrical standards and practices. For instance, if the smaller bus did not need protection, it could lead to serious safety hazards. Directly connecting the smaller busway without protection or resizing conductors does not adhere to safety guidelines that mandate overcurrent protection for circuits when there is a significant difference in ampacity.