French term (edited): thermique

There are various terms available, depending on exactly WHAT form it takes and WHERE it is located.

On certain individual appliances, it might be a 'thermal cutout'.

But in an eelctrical cabinet, it sound more like a thermally-tripped circuit-breaker — the thermal technique tends to be used for slower-acting devices designed to protect against prolonged, but possibly marginal, overloads; many circuit-breakers use a combination of thermal and magnetic techniques.

I don't now about your instance with 'tombé' — it is possible it might be soemthing that has 'dropped out', but it's hard to tell without more details; it's also perhaps important to know if this 'thermique' is actually LOCATED IN the 'bac de refoulement' — note that it is 'du', which could certainly suggest it is simply the 'thermique' for the bac, but not actually located in/on it.