First, the ultimate temperature of oven and tank is 55℃, we just compile this temperature in the software. PT100 is the temperature testing element, is hard to break.
Second, it’s October now, the weather is nice and cool, the temperature of ambiance won’t affect the temperature control of oven.
It means the oven keep on heating when the temperature rushed to 55℃, you can check if the temperature will low down after you reset the oven temperature at 0℃. If won’t low down, it means heating won’t stop, but it shouldn’t be. Then check whether the heating element has 220V voltage with plug-in board, if have, it means the relay on the control board is breakdown, you need to change it.
If not in a hurry, there comes another solution: for a new TCD instrument, there has a spare relay for TCD heating (the right side of J5), you can separate it and then changed.