RCD’s or Residual Current Devices work by detecting any differences  in the electrical circuit. Any differences between the live in and the return neutral are detected and the circuit is instantly broken. They can detect very small current leakages, typically between 5 & 30 milliamperes, and by breaking the circuit in less than 30 milliseconds they can prevent electrocution. The fitting of an RCD on a narrowboat is now a condition of the Boat Safety Scheme.

The consumer unit may also give overload or short circuit protection to wiring in the form of circuit breakers or MCB’s. The circuit breaker must be rated to carry the current of any load as of course, so must the cabling itself.

That accounts for the most basic of narrow boat shore power systems. But what if we need 230VAC when we are away from shore power and we want to use the same ring wiring.

Well we need a changeover switch from the shore power system to the narrow boat based 230VAC generation system. Switches can be either manual or fully automatic sensing when shore power is unplugged and inverter power comes into play.

Typical methods of on-boat 230VAC power generation are via the DC system through a DC to AC inverter or directly from a generator such as a wind turbine, an engine driven alternator or a dedicated on-board gen-set.