What is the minimum percentage that the inside diameter of a casing must be larger than the outside diameter of the largest conduit?

The correct answer indicates that the minimum percentage that the inside diameter of a casing should exceed the outside diameter of the largest conduit is 10%. This requirement is critical for ensuring proper installation and functionality of the conduits within the casing.

This 10% margin allows for necessary clearance, which facilitates the installation, maintenance, and potential replacement of the conduit. Adequate spacing is essential to prevent issues such as friction, bending, or damage during conduit installation and operation. Additionally, it helps in accommodating any expansion or contraction of the materials due to temperature variations, as well as avoids issues with cable movement or potential damage caused by contact with the casing.

Proper understanding of these spacing requirements is vital for ensuring reliability and longevity in outside plant installations, an essential aspect of the BICSI Outside Plant Designer curriculum.