The evaporative cooling mode triggers the pump. You’ll hear the water circulating around the unit. This mode is used both for summer cooling and winter humidifying. The difference is the fan power you use at the same time. If you select evaporative cooling and also a high or turbo fan setting (and add ice as well), then you’ll have max summer cooling. If you select evaporative cooling, but choose a low fan setting or even sleep mode, then you’ll achieve a gentle humidity. The fan will be just powerful enough to emit moisture but won’t have much cooling power.