Inept, there is no DC essential power selector switch on the Classic. There is however an AC Essential power switch which selects the source for the Essential AC bus and is usually selected to Normal position. DC bus isolation relay opens automatically if the ESS AC is selected to Gens 1, 2 or 3 and forms the DC buses into two parallel pairs. You are getting confused with the three DC Bus Isolation switches, one of which is the Essential (DC) bus isolation switch.