@kimot I am not handling that situation. I'm taking for granted ssr will do his job. Maybe there's some ssr safety topic I'm unaware? Suggestions for a v3.0 are welcome. About the temperature measuring... I use two sensors. The one in the board protects electronics from temperatures beyond design (60°C). It's near the ssr because the ssr's derating curve is the most limiting condition. The control sensor is placed in the bottom of the heater. It connects to the board through a 3 pin header connector.