SMALL BOATS ELECTRICAL INSTALLATIONS

Size matters John - amongst other things.

Try EN 60093-507 for ships - Pleasure Craft 24 to 50 metres length.

EN ISO 13297 - Small Craft up to 24 metres length.

The RCD (no not that one) The Recreational Craft Directive 2020.

Regards

Geoff Blackwell

My experience of yachts is that they are similar to a motor vehicle: i.e. 12 V DC with an alternator on the engine and, sometimes nowadays, a windmill or solar panel.

As Geoff says, BS EN ISO 13297:2021 applies (both to 12 V DC and 230 V AC).

For a small and simple installation at mains voltage on a boat, I would proceed as for a caravan.

For an ELV installation I would follow accepted good practice, including 2 pole wiring, NOT earth return as is used on motor vehicles. In many cases, oversized cables will be needed to minimise voltage drop.

On all but the most basic craft, essential equipment should be duplicated with no common point of failure. For example duplicated feeds from two batteries to radio equipment, bilge pumps, and navigation lights.

For small and simple circuits, a good rule of thumb is to size the fuse at twice the running current, and then size the cable at twice the fuse size.

Example, bilge pump uses 8 amps. Use a fuse of about twice that, 15 amps or 16 amps. Then select cable good for about 32 amps, probably 4mm.

Consider possible corrosion at electrical terminals, especially if the boat is used in salt or brackish waters. Protect all cable ends and do not allow joints to get wet. Use appropriate gunge like grease or silicon sealant etc. Duplicate bilge pumps in case one becomes blocked, seized or fails in another way. Have independent torches and backup of essential equipment like the marine radio etc. in case of 12 Volt failure or a dead or dying battery.

Consider corrosion of external parts like propellers and steering gear due to electrolysis.

Only supply steel hulled craft via a mains TT earthed supply, NOT P.M.E.

Z.

Geoff got the number wrong - it is 60092-507 which covers small craft from 24m to 50m but is primarily for ac three phase. The RCD is applicable to all craft sold for non-commercial use, from jet-skis to canal boats and beyond.

The RCD specifies which standards provide presumed compliance (i.e. if you follow the standard your installation is presumed to comply with the directive) but there is still a need to follow best practice in areas not covered/not clear in the standard.

That said, it also depends on whether you are looking at a new vessel or a modification to an existing vessel since existing vessels tend to work to the rules at the time of build, potentially even if you are doing a complete new installation on an old vessel, though that is a much more complicated issue and following the latest rules is much safer, in all senses of the word.

Alasdair

My copy of the standard I have quoted (dated 2000) has a scope which covers Ac single & three phase and DC.  It is for vessels from 24 to 50 metres. It also covers vessels less than 24 metres for 3 phase systems only.

The PME restriction applies to all craft, not just steel hulls.

But is more critical to all metal hulled boats as there is more exposure of metal parts. Glass fibre (GRP) hulled or wooden hulled boats pose less risk.

Z.

It not a case of critical - it is prohibited in law by the Electricity Safety, Quality and Continuity Regulations.  These are statute - compliance is not optional.  They will probably send you to the colonies if you transgress.  To be more exact - the Regulation 9.4.  Places a duty on the distributor - the text is:

The distributor shall not connect his combined neutral and protective conductor to any metalwork in a caravan or boat. 

Yes I knew that, why did you think that I didn't?

Z.