Im wireing a submersible well pump that is over 500ft deep. The pump at normal depth requires a 20amp 240v circuit. Because it is so deep the well contractor ran a #8 wire to the pump all the way to the pressure tank in the basement to allow for voltage drop. Does this #8 wire need to go all the way back to the panel box or can I run #12 to pressure tank. And do I still use a 20 amp breaker? Or should I use a 40A.