Thanks Franco ! I check that std thermostat opening temp it`s about 82 cel degree. Sierra fan switch have 88 cel degree switch on fan point and he is switching off fan on 77 cel degree, he have only 1 switch on point. Std ESCOS fan switch have 2 switch on fan points. 1 gear switch on fan about 95 cel degree and switch off on 90 degree. 2 gear switch on fan about 105 cel degree and switch off on 100 cel degree. IMHO Sapp. fan switch is good reference.