I have the same set up. My fan is on most of the time in the summer because it is hotter out. I think the fans turn off somewhere around 45C for the system temperature. You can check going to the status page when you login via web. I know when it is hotter in my room, the fans will run faster, even when the drives are idling. How loud is it? If it seems like it is running full speed, then I would suggest you return. From what I can tell it really depends on the room temperature. I know somewhere on the forum, someone modified the front plate to allow more air in. I will try to look for it.