IEC 61439 is a standard developed by the International Electrotechnical Commission (IEC) that covers design verification for low-voltage electrical products and assemblies. Proper planning of safety distances in low-voltage busbar design and installation is critical for ensuring electrical performance, operational stability, and equipment safety. The IEC 61439. The test shall be carried out according to IEC 60068-2-2 Test Bb, at a temperature of 70 °C, with natural air circulation, for a duration of 168 h (7 days) and with a recovery of 96 h (4 days). - The UV radiation causes deterioration of synthetic material use for enclosures. Procedure: UV Test. The IEC standard for busbar sizing provides detailed guidelines to help engineers select appropriate busbar dimensions.