How should fittings in Class II lightning protection systems be secured?

In Class II lightning protection systems, fittings should be secured by compression under bolt or screw heads. This method ensures that the components of the system are tightly held together, creating a strong mechanical connection that is essential for the integrity and reliability of the lightning protection system. A secure fitting minimizes the risk of loosening due to vibrations or thermal expansion, common in outdoor environments where these systems are often installed.

Using compression under bolt or screw heads allows for proper electrical continuity, which is critical for the safe dissipation of lightning energy through the system. This helps to ensure that the entire system functions effectively in protecting structures from lightning strikes.

In contrast, other methods like adhesives or welding might not provide the necessary flexibility or could compromise the integrity over time due to changes in temperature and environmental conditions. Loose connections would also fail to provide the necessary structural integrity and electrical continuity needed in a reliable lightning protection system. Thus, securing fittings through compression under bolts or screws is the most effective and standard approach in these systems.