I understand the distinction between standby and prime ratings for generator sets, but am having trouble finding specific delineations of what constitutes a continuous duty generator. Besides the obvious difference, it seems that prime units are rated for over 500 hours of operation per year. But at what point does a generator need to be classified as "continuous"? Is it a particular number of continuous hours in a row? In addition to the usual standby and prime ratings, I'm now seeing some manufacturers list continuous ratings for each genset (even lower than the prime rating), but without a good explanation.


Oh okay, Cummins lists this info:

Emergency standby power (ESP): Applicable for supplying power to varying electrical load for the duration of power interruption of a reliable utility source. Emergency Standby Power (ESP) is in accordance with ISO 8528. Fuel Stop power in accordance with ISO 3046, AS 2789, DIN 6271 and BS 5514.

Limited-time running power (LTP): Applicable for supplying power to a constant electrical load for limited hours. Limited Time Running Power (LTP) is in accordance with ISO 8528.

Prime power (PRP): Applicable for supplying power to varying electrical load for unlimited hours. Prime Power (PRP) is in accordance with ISO 8528. Ten percent overload capability is available in accordance with ISO 3046, AS 2789, DIN 6271 and BS 5514.

Base load (continuous) power (COP): Applicable for supplying power continuously to a constant electrical load for unlimited hours. Continuous Power (COP) in accordance with ISO 8528, ISO 3046, AS 2789, DIN 6271 and BS 5514.


Anyone know what those ISO documents say? :-?