But they connect pin 2 of the 555 to the positive supply all the time, so the 555 won't do anything.Gregory said:The two Thermistors are for heat detiction to turn the 555 off at the set temperature.
Why do you have two thermistors in parallel?
Instead of the 555 you should use an opamp wired as a comparator. Its output would be continuous when the temperature exceeds the set amount. If the sound from the piezo buzzer is annoying then it can be turned off temporarily with a flip-flop circuit and your pushbutton.