BS EN 10133 is what you need for the 12V (or 24V) DC side of things, and BS EN 13297 for the 230V bits. I'll try to summarise the main bits of the former.
Blue Sea Systems do good quality panels and switchgear (at least, their DC stuff is good, don't know about their AC stuff). I upgraded the wiring on the last boat I owned.
I lived on narrowboats (prior to getting the Zeeschouw) for about 10 years.
Some random bits from BS EN 10133 (that's different from BS7671):
- hull can be grounded (usually is, at the engine) but obviously you can't use the hull as a conductor. Only grounding the negative conductor in this way is permitted.
- 10% voltage drop permitted, however, some circuits will "typically require" 3% or less: panel boards, nav lights, bilge blowers, bilge pumps, other equipment where specified by manufacturer
- batteries shouldn't be able to move more than 10mm (horizontally or vertically). You need to supply leaking electrolyte containment for tilts up to 45 deg.
- need a battery-disconnector switch on positive conductor, easily reachable, as close as practicable to the batteries (exceptions for things like solar panels, bilge pumps etc as long as they have a protective device close to the battery).
- flexible or stranded insulated conductors, fire-retardant material, e.g. not supporting combustion in absence of flames
- conductors in engine room at least 70C and rated oil resistant, or protected by insulating conduit or sleeving
- minimum support distance 450mm, or 300mm on cable to battery switch.
- minimum size for singles = 1mm, for multi-core flex 0.75mm (except for panel boards, where 0.75mm singles can be used)
- not in same containment as AC wiring. If not separated by partition etc, then minimum distance in free space = 100mm
- DC negative conductors should be black, or yellow (unless you're using black in AC, in which case, use yellow). Black or yellow must not be used for DC positive. Avoid use of brown, white or light blue in DC system, if AC is present on boat.
- terminate appropriately, e.g. "no bare wires to stud or screw connections"
- socket outlets should not be interchangeable AC and DC
The usual restrictions about IP ratings etc apply.
In practice, invest in lots of flexible PVC conduit. Run your DC singles through it (generally red and black), and (generally) AC flex through it (separate ones, obviously) too, for getting it around the boat.
Hope that's helpful
