"24V DC Cooling Fan" operation is changed as the case of heat, at a slower speed operation, the fan will have less noise and consumes less energy. In most of the design requirements, the fan speed operation in a few hours after the air temperature is usually lower than the maximum design temperature value. Under normal circumstances, low-speed operation of the "24V DC Cooling Fan" can be enough to complete its work. But in the selection and installation should also be considered: DC fan temperature changes slower fan speed changes are slow, will not suddenly change "24V DC Cooling Fan" speed and noise. The reaction time depends mainly on the length of the sensor of its thermally-induced sensitivity.