Appendix C: Grounding and RF protection110 General about marine DC systemsC.2 General about marine DC systemsC.2.1 Wiring systemsTwo basic wiring topologies are used for marine DC system grounding: Two-Wire Return System and One Pole Grounded Return System.C.2.2 Two-wire Return SystemThis configuration implies that no part of the circuit, in particular the batterynegative, is connected to any ground potential or equipment. The system istotally isolated and includes engine sensors, starter motors etc. Thisarrangement is preferred for steel and aluminum vessels.BATTERYALTERNATOR STARTERMOTOR+ -BATTERY+ -B+B-SWITCHBOARDSWITCH(ON/OFF)STARTER RELAY(ON/OFF)OUTGOING CIRCUITSGAUGESENGINESENSORS-+ISOLATOR
