Master Electrician Practice Exam

A panelboard is limited to 42 overcurrent protective devices when it is which type?

1. Single-bus

2. Split-bus

3. Dual-bus

4. Multi-bus

The correct answer is: Split-bus

When considering the types of panelboards and the limitations on the number of overcurrent protective devices (OCPDs), the split-bus design stands out. A split-bus panelboard typically divides the panel into two sections, allowing the first section to contain a limited number of circuits fed directly from the main supply. The maximum limit of 42 OCPDs in a split-bus configuration is a result of the specific requirements set forth in the National Electrical Code (NEC), which aims to ensure safe electrical practices and manageable load distribution. In a split-bus panel, one section can usually serve lighting and appliance loads, while the other is reserved for larger loads that might require direct connection to the main power source. This design, while efficient, imposes the 42-device limit to avoid overcrowding and to maintain clarity in the electrical system organization. Each circuit breaker plays a crucial role in protection and load management, and the split-bus design ensures that the system remains within safe operational boundaries. The other types of panelboards have different configurations and limits, allowing for greater flexibility in OCPD arrangements. For instance, single-bus and dual-bus configurations typically allow for more than 42 devices, while multi-bus setups often have varied