Surface Internal Source Location Temperature Higher Than Source

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Hello everyone,

I am modeling a small office with one thermal zone using E+. I am using ZoneHVAC:LowTemperatureRadiant:Electric to be in embedded in one of the walls, I set the Temperature control type to be Mean Radiant Temperature. The mean radiant temperature is set to be 25C. After running the simulation, the Surface Internal Source Location Temperature is much higher than mean radiant temperature in some cases it reaches 80C, while the outside temperature is -8C and the mean radiant temperature is 25C. May I know why is that happening?

Thank you very much