scope:

This document specifies a method of air temperature-rise calculation inside enclosures for low- voltage switchgear and controlgear assemblies or similar products in accordance with their respective standard. The method is primarily applicable to enclosed assemblies or partitioned sections of assemblies without forced ventilation. However, some technical guidance to adapt it for the use of forced ventilation is given in this document. The results obtained by using this method are directly influenced by the accuracy of the evaluation of power losses used as inputs to perform the thermal calculations. NOTE - The air temperature within the enclosure is equal to the ambient air temperature outside the enclosure plus the temperature-rise of the air inside the enclosure caused by the power losses of the installed equipment. For the method to be applied, the maximum daily average ambient air temperature outside the assembly at the place of installation must be specified between 10 °C and 50 °C. The maximum daily temperature shall not exceed the maximum daily average temperature by more than 5 K. Several annexes in this document provide guidance on how temperature-rise within assemblies may be affected by influences which are not considered in the calculation method included in this document, for example, when the assembly is subject to solar radiation. In such cases, different means of verification to that given in this document can be required to ensure a definitive result and verification of the design.