Sills or curbs in transformer vaults, shall have a minimum height of __________.

The correct height for sills or curbs in transformer vaults, set at a minimum of 4 inches, is designed to provide adequate containment for any liquids that may leak from the transformers. This containment is vital in preventing spills from spreading and causing potential hazards, including environmental contamination or electrical hazards.

Transformers can contain insulating oil, which, if leaked, needs to be contained to minimize risks. The 4-inch height establishes a sufficient barrier in typical vault applications. It balances practicality with safety requirements, ensuring that maintenance or oil leaks are less likely to create a dangerous situation. Higher barriers, while they may offer increased containment in theory, could complicate access for maintenance personnel and require more extensive engineering.

Understanding these requirements is essential for anyone working with electrical installations, particularly in relation to safety and compliance with industry standards and local codes.