A longer cable won't just catch fire, because the power dissipation per unit of length is the same regardless of overall length. Imagine the most extreme case -

A longer cable won't just catch fire, because the power dissipation per unit of length is the same regardless of overall length. Imagine the most extreme case - a cable so long the voltage difference is 0V at the end. It's basically just a very long resistor dissipating 60W. But each meter of cable will be dissipating the same power as every other PoE setup. Looping the cable or putting it in a confined space could cause issues. The cable could then catch fire even though it appeared to be operating normally to the PoE controller.