IEC/PAS 61156-1-4:2010(E) is covering exclusively four-pair data grade cables and is intended to provide a test method for the determination of the maximum attained conductor temperatures which occur due to the deployment of the IEEE protocol for PoE /PoEP. It gives as well the required background information about the thermodynamic behaviour of such bundled cables, if they are located in areas with restricted heat dissipation, a reality which occurs in every installation situation. However, only the basic principles are given, as the rigorous application and solution of these problems fall into the relevant cabling standards.