While reverse rotation is most commonly associated with hot swapping components it is not just limited to this usage case. When starting up an assembly with multiple fans, there may be risk of reverse rotation as well. The best prevention for reverse rotation at starting up is to have all fans start rotating at the same time. This prevents any slower starting fans from reverse rotation caused by the fans that started earlier. In some instances it may also be required to start up all fans at a slower speed first prior to transitioning to the maximum operating speed. For applications that use multiple fans of different sizes, starting up lower performance fans first will help prevent them from getting over powered by the stronger or larger fans. Usage cases may vary so if the customer experiences reverse rotation after reviewing the previous recommendations, feel free to reach out to the local Sanyo Denki representative for assistance.