Many people "220V AC Cooling Fan" is not well understood, in fact, the operation of DC fan with the conditions of heat and changed to slow speed operation, the fan will have less noise and consumes less energy. In most of the design requirements, after the "220V AC Cooling Fan" speed operation hours are usually lower than the air temperature maximum design temperature values. Under normal circumstances, low speed cooling fan can be enough to complete its work. However, when selecting and installing should also be considered: the fan when the temperature change is slow, slower fan speed changes will not suddenly change "220V AC Cooling Fan" speed and noise. The reaction time mainly depends on the length of its sensor to the heat-sensing sensitivity.