Setup equipment: Spot check manual data collection Type K thermocouple + K-Type adapter + Fluke 189 Fluke 62 max+ Automated data collection Omega OS136 infrared sensor + picoscope 2205A run as a data logger Type K thermocouple + K-Type adapter + Keysight 34465A DMM + BenchVue Omega OS136 located 9 cm above transformer cover center. Measurement spot size 1.5 cm. Type K thermocouple located inside transformer cover in free air approximately 1 cm below the top surface, between transformer and cover side wall. The thermocouple was slipped into the space through the chassis slot for transformer wires. Setup picture: Automated measurement data Spot check manual measurements correlated well with the automated measurements. It should be noted the Fluke 62 max+ measured consistently 2 ~ 3 °C below the Omega OS136 which is within the specified accuracy tolerance. Ambient temperature was tightly controlled to 20.8 °C with the new HVAC system. It would appear the free air temperature inside the transformer cover is 3 ~ 4 °C higher than the cover top surface. My suggestion would be to keep the transformer top cover surface below 46 °C and certainly no higher than 50 °C. Following this suggestion should allow sufficient margin for the transformer core temperature to remain within operating limits.