I spent 24 hours at 500Mhz and 3.3Th/s.
I changed my room and very poor result . Back in the first room.
For the moment, its always stable at 500Mhz and low HW. (0.09% !!).
(5s):3.328T (1m):3.293T (5m):3.269T (15m):3.273T (avg):3.214Th/s
 A:7611392  R:6144  HW:6909  WU:44915.7/m

http://www.image-heberg.fr/files/14042894687622.png
http://www.image-heberg.fr/files/14042894687639.png

PSU is generic (LDLC.COM) but stable and 80+. (2250 watts electric meter).
I ordered 6 x Corsair AX860 Modulaire - 860W to avoid having 5 PSU...
I try with an Corsair AX850 but PSU has broken down... (Only one Asic and controller).

I did not understand the functioning of voltage and I have not changed.
Maximum temperature for the day : 101°
I'm going to lower frequencies for the next days, 34° for thursday...
They will be installed in datacenter Monday.