As long as your transfer switch is working, it will switch to the generator power as soon as it comes online which turns off your incoming shore power, BUT doing this is hard on the transfer switch depending on how much "stuff" is operating when the transfer occurs. Some may disagree, but I NEVER switch to generator power without turning off the breaker from the incoming shore power. I want my transfer switch to have a very easy time making the transfer.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof