This is a fixed 55'C switch set to open-circuit once that temperature is reached. I checked it on our test bench and it tripped at 55.6'C and was able to be manually reset once the temp fell below 55'C. This is a recommended upgrade to my make/model spa pool. The original came with an OT switch which was fixed at 45'C which, when new would have been ok. I suspect that over time it became faulty because it was operating with monoteneous regularity even though my pool temp was below 35'C.
Anyway, the replacement switch works perfectly well and gives me a greater margin while maintaining a respectable safety margin.
