RIG Shutdown

Hello,

PSU: EVGA 1300W
GPU: 4x RX480 8GB MSI + 2x RX480 8GB SAPHIRE NITRO+
RAM: 8GB DDR3
MB: ASROCK H81 PRO BTC
SSD: 120GB KINGSTON
OS: WIN10


After run Claymore, the rig start mining normally till 30 minutes (~150mhs, never OC) and then it shutdown (not restart, shutdown)

GPU temperatures shown in the cmd doesn't exceed 70C -- the rig is in a room with A/C, i don't think temperature is the problem.

What do you think is the problem?

Thank you

Update: PSU input is 110 VAC - Could this be the problem?