Thanks for the reply. I will check out my other controller and will decide how to proceed. I am thinking a 3 pole double throw switch on the AC input line and also breaking the common may be a better solution . Than way the the off system will be completely floating if there are no earth grounds attached to either PCB. Right now there are no earth ground connections. BTW I have the unit on order (not here yet) and will advise what connections are made to my current Irritrol Rain Dial-R controller. I am an EE and will reverse engineer the schematic of the Irritrol before making any common connections so that nothing bad happens. There are MOV’s on the Irritrol PCB which would also help protect the Open Sprinkler.