The temperature outside yesterday was 97 degrees. I was cleaning the pool skimmer basket and noticed the water was very warm. Much warmer than the fairly constant 85 degrees it is without the heater on. I checked out the Pentair Mastertemp 250 high performance heater and it was turned on to Spa at 95 degrees. Facts: The heater has not been on since June. I don’t have a spa so the spa button has never been pushed. I have never turned the temperature higher than 85 degrees. 

Is it possible that the heater somehow came on by itself and defaulted to these settings?  Because it’s difficult to imagine that someone did this intentionally despite the equipment not being locked up.