The IEC requires a minimum clearance of 14 mm for systems up to 690V. Creepage distances vary based on pollution degree and material used. This avoids tangling and improves cooling. But what exactly does it take for these critical components to earn international certification? Let's unpack the requirements that transform ordinary electrical. Design requirements for low voltage distribution boxes cover NEC, IEC, and safety standards to ensure reliable, compliant electrical installations. You must make safety your top priority when working with low voltage distribution boxes. Design requirements help you follow important standards like. 1. 1 Pre-installation Requirements for Transformers and Substations: - The indoor ceiling and wall finishes should be completed with no water leakage. - The foundation should be inspected and accepted as qualified, and the conduits embedded in the. ents), and the electrical equipment, formed by the internal connections and by the incoming and outgoing termina is regard, there has been an evolution which has resulted in the replacement of the previous Standard IEC 60439 with the present Stand rd IEC 61439.