What condition must be met when using ENT with listed floor boxes encased in concrete?

In this scenario, the correct condition for using ENT (Electrical Nonmetallic Tubing) with floor boxes encased in concrete is that it is common practice to use them. This implies that there are established guidelines and industry standards that support this practice, ensuring both safety and functionality in electrical installations.

When ENT is used with floor boxes in concrete, it is typically designed to provide protection for the conductors while allowing for the necessary flexibility and durability within the concrete environment. The practice is often guided by local code requirements, manufacturer recommendations, or established industry practices.

Using ENT in this manner ensures that installations are compliant with necessary electrical codes and guidelines that prioritize safety, efficiency, and longevity of electrical systems. It reflects an understanding that certain types of electrical equipment and configurations are commonly accepted as safe and effective under specific conditions, such as being encased in concrete. This common practice is what makes the answer valid and applicable in real-world scenarios.