At 11:50 UTC the NI TCS Chiller went in failure (HPC - High Press Cutout. The refrigeration may need servicing).
The Guardian system swap the NI with the BCK one. Lasers always in operation.
After few check we decided to swap the NI chiller with the spare one provided by Roma group and available in TCS Chiller room. 
Standard state recovered at 13:00 UTC.
Tomorrow Nardecchia will contact the company for the reparation.