Busbar Sizing Guide
This guide is for assistance only. All figures used are only suitable for panels were ventilation  and temperature rise testing has been established. Only if the busbar bracings are suitable,  are the temperature rises shown to be allowed. It is our recommendation that the figures for  normal switchgear should be the first column (35 Deg C Ambient with 50 Deg C temperature  rise) and a 10% de-rating factor used for non ventilated cubicles. Overleaf are some of the  details and design requirements that have gone into the calculations for the following values  which have been taken from the Copper Development Ass. publication No 22. 
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Busbar Sizing Guide