First I want to say hello to all here. I have been a member here and reading and learning a lot the last few weeks. In late Oct this year I bought a used 2012 Cyclone 300C with a 5500 Onan. Over the last forty years this is the tenth RV I had, but only the second one to have a generator. The service tech that did the walk though with us told me not to start the generator while the power cord was plugged in to shore power. He said it could cause a spike that could damage some of the electrical components. I keep the trailer plugged in at home and understand that I need to exercise the generator periodically. Is it really necessary to unplug from shore power before I start the generator or will it automatically switch over and cause no harm?