ISO 8528 is a standard that determines the operating conditions of generators and requires the generator set to provide the rated power given on the label as a continuous output power at an ambient temperature of 25 degrees Celsius. Although the generator radiator is given as 40 degrees Celsius in the document records, alternator copper losses and the heat emitted by the radiation on the engine and exhaust pipes cause the incoming air to rise to a value above the ambient temperature (30%). This causes a power decrease on the diesel generator.
If it is desired to prevent this power decrease, then the radiator system is moved away from the diesel generator and provided directly to the ambient air suction. Therefore, if the radiator is designed for 40 degrees Celsius, it will run at that temperature with no power decrease.