I installed a Hughes 30 Amp Spike Power Watch Dog with The Shut-Off. The install went great. But I found issues. The unit would trip the GFCI at the campground each time I connected it. Months before installing the Watch Dog, I simply used a Taiss TA106B Socket Receptacle Tester, it displays voltage and will indicate bad wiring. It was kind of nice having a voltage readout so I left it connected all the time to the camper. IF the Receptacle Tester is plugged in and with the new hardwired Watch Dog, IF I connect to a GFCI, it will trip after a few seconds. Here's theory: the GFCI is looking at the hot and neutral and expects to see what goes in to be what goes out. The Watch Dog takes a little of that current and uses it to test for a fault, so tiny bit goes back down the ground wire. The Taiss TA106B does the same, the 2 together is enough to trip the GFCI......after some seconds.