I have the hard wired 30A progressive. I just realized this after a year but the slide switch on the display not only turns the flashing display off, it seems to bypass some of the circuitry.Last time out I was just plugged into a 20amp house circuit and had the switch off. All was well. When I turned the switch on ,I got errors and cut power to my TT. With 150' cord I would imagine there would be low voltage but all we were using were lights, fridge and water pump. So the switch can also bypass the unit when you really don't want the protection. I am guessing this will not bypass the unit if it malfunctions.