because u need to cool down the rest of the mining board components, not just the asics! maybe some redundancy too;)
It also seems that the ASICs don't have an internal temp probe like CPUs and GPUs there is a LM57A sensor on the reverse of the board to monitor tempratures, the fan keeps this chip cool so honest throttle back your ASICs.
I have recently purchased one of these kits and put in a single S5, left it overnight on a de-ariation cycle, (pump timed to run for 30s on and 30s off for 8 hours) along with tilting and tipping the chassis to ensure all air has been removed.
I booted the miner up this morning and blade 1 was reporting 80c and blade 2 at 67c, the first blade is getting the least amount of airflow due to the position in the case so I am running my S5 as a single blade at the moment and have ordered some ramsinks to stick on the LM57A chip as per goxed advise.
At those temps my water temp is only 30c and the water block is cool to touch but the miner still throttles right back and sits down if I leave board 1 connected, I hope the ramsink will decrease the temperature readout and mean that I can run both blades without shutting down.
https://i.imgur.com/Mhua6Dy.jpghttps://i.imgur.com/edKqNHV.jpgThe above pictures show the chip that needs cooling down, the rest of the components don't really need too much cooling (apart from the ground pads/heatsink pads) on the backs of the ASICs but moderate airflow will be fine across those pads.
EDIT: This is my stats page with only one blade powered and the water at 30c
http://i.imgur.com/kvjjlql.png
