@lis610 I have found with a 499K resistor the range is reduced to about 1.2m in a ABS box.
With a 1Mohm it was about 3m, I do not have many high value SMD resistors to experiment with but the lower the value the lower the range.
Just tried with a 333K and it operates about 0.8m in free air.
@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.
