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 required for the installation of the smaller bus?

For the installation of a smaller bus, specifically in this scenario where a 300-foot run of 800-amp busway is reduced to a bus rating of 200 amps for the last 20 feet, it is critical to protect the smaller bus with an overcurrent device. This requirement stems from the need to prevent potential overloads that could occur due to the smaller bus's reduced ampacity.

When the bus rating decreases, the smaller busway has a lower capacity to handle current without overheating or becoming damaged. An overcurrent device, such as a circuit breaker or fuse, serves to automatically disconnect the electrical supply in cases where the current exceeds the safe limits of the smaller bus, thus ensuring safety and compliance with code requirements. This protective measure is essential not only for protecting the smaller busway itself but also for mitigating fire hazards and protecting downstream equipment.

It’s important to note that grounded separately, connected directly without precautions, or having a higher ampacity rating are not appropriate actions in this situation. The emphasis must remain on the necessity of overcurrent protection when reducing ampacity in this manner.