I did something similar the first day I got my thermostat for the UTE mat- plugged in the CHE by mistake, and it was sitting on top of one of the glass panels I commissioned for the top of the tank. Heard a weird sound and smelled a bit of something burning beforehand discovering that it had cracked the glass panel underneath with such a hot temp! (had it turned away up because the UTE wasn't getting any hotter lmao) Was not happy about having to buy another one :'v