I recently built my pc and it is my first time using an AIO (h100i Elite Capellix XT ) and after getting everything up and running a couple of days ago I noticed one of the fans on the AIO is upside down. so one is blowing into the case while the other is blowing into the radiator. So far I've had great performance and it will be a bit of a hassle to take it out again so I don't want to do it unless I know it to be neccessary.