For busbar sizing, the primary references are IEC 61439 (for low-voltage switchgear and controlgear assemblies) and IEC 60287 (for current-carrying capacity of cables). The IEC standard for busbar sizing provides detailed guidelines to help engineers select appropriate busbar dimensions. This ensures that systems operate reliably without overheating or causing electrical hazards. The International Electrotechnical Commission (IEC) issues globally accepted. IEC 61439 is a standard developed by the International Electrotechnical Commission (IEC) that covers design verification for low-voltage electrical products and assemblies. The IEC 61439. (1) Add Top Hat Rails, catalog number 141A-AHR45, page 23, to a module when a 141C-X40 (Adapter Extension Module) is being added to typically support the contactor on a 3 component starter. See also CrossBoard Universal Adapter Installation Instructions, publication 141C-IN004 for more information. 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). Procedure: UV Test. Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 November 2014 Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 Companies involved in the preparation of this Guide Acknowledgements. The busbar sizing calculator determines the required busbar dimensions based on the continuous current rating, short circuit withstand, and thermal limits for switchgear assemblies. The current rating is calculated from the conductor cross-sectional area, material (copper or aluminium), and maximum.