What is the construction requirement for the floor of an electrical vault for conductors operating over 600 volts, nominal?

The construction requirement for the floor of an electrical vault housing conductors operating over 600 volts, nominal, specifies that the floor must be a minimum of 4-inch-thick concrete. This thickness is crucial for several reasons, including providing the necessary structural support and ensuring fire resistance and safety for personnel as well as for the electrical equipment housed within the vault.

Concrete is favored in this application due to its durability and capacity to withstand not only the weight of the conductors and equipment but also the potential impacts and stresses they may encounter. A 4-inch thickness strikes a balance between adequate protection and resource efficiency, making it a widely accepted standard in electrical installations involving high-voltage systems.

The other options, such as 2-inch-thick plywood or more substantial requirements of 6-inch or 8-inch-thick concrete, do not align with the established standards and regulations that govern the design and construction of electrical vaults for such applications, making the selection of 4-inch-thick concrete both practical and compliant.