I would recommend going to the ASUS site and download the BIOS guide. Lots of good info. there. It is located under the Manual & Document section.
I asked directly in ASUS chat support and they said setting setting the CPU FAN monitoring to ignore is the way to go.
I also went to the shop who assembled the computer and they've said the same thing, thats how they made the build originally.
Also interesting to notice that the technician at the shop said I should leave it to auto-dected instead of choosing DC mode. That one I'm not so sure but I'll trust them and leave it that way.