Spec me a proper, safe shore-power system please

[Babylon]

Presently have an orange shore-power lead that feeds down the hatch to a loose 13A domestic socket with a cheap domestic RCD plugged in, then to a loose 4-gang extension, into which I currently plug a C-TEK 7amp smart charger, plus whatever else is needed at the time (e.g. a small electric kettle, a small oil-filled heater, a fan-heater, laptop, phone-charger, hairdryer, etc).

All this crap of cables and trolling extensions needs to be put away before getting underway, it isn't properly safe, it isn't earthed or isolated, and there is no 240v ring-main to safely distribute power to fixed sockets around the boat. The 7amp smart charger should also really be upgraded to a 15amp unit for the size of my battery bank, and the old 300w modified sine-wave inverter upgraded to a modern 1000w unit before forming part of the ring-main.

Boat is normally kept on a mid-river mooring away from stray currents, has a wind-generator to keep the 2x110Ah domestic bank and the engine-start battery topped up, and the Beta 25 engine has a good 70Amp alternator fitted. The VSR ensures the engine start-battery on its completely independent circuit is always charged first, whatever the source.

So, aside from needing a water-proof flush socket to fit into a cockpit side-locker, an RCD to fit alongside the bigger charger and inverter down below, and cabling and domestic-sockets to run around the cabin, what else do I need? Do I need marine-grade cabling for the ring-main? Where do I earth the RCD to? Will I need to fit a galvanic-isolator and where in the system does this go?

Finally, what is so special about Marinco plugs and sockets - what's wrong with the cheaper normal blue/white kit (except that in rough weather my cockpit side-lockers can fill with green water)?

Cheers

 

[pvb]

Most boats don't have, or need, a ring mains - radial wiring is fine. Use multi-strand flexible cable rather than domestic cable.

I'm sure you realise that you actually need a plug in the cockpit locker, as the boat end of your shorepower lead has a socket on it.

An RCD works by sensing an imbalance in the live and neutral wires, and doesn't need an earth connection in order to work.

If you plan to routinely leave shorepower connected, a galvanic isolator could be a good idea.

Be very careful if you plan to use the inverter to power the sockets; it must be wired so that you can't have shorepower and inverter power simultaneously. Some people achieve this by having a shorepower-type connection on the inverter's output, and plugging it in to the shorepower inlet in the boat, thus ensuring that the shorepower lead has to be disconnected first.

 

[Jabs]

Good advice. I might use 'arctic' cable for the shore line as well as for wiring.
Don't forget your max is likely to be 16a so maybe a low (600w) kettle, hairdryer etc rather than domestic items.
You might save money buying the bits from a caravan shop rather than a chandlery.

A galvanic isolator is a great idea if you spend much time hooked up. It is the first thing after the shore power plug.

You can use a simple two position switch for the inverter/shore power.

Good luck

Tony.

 

[VicS]

Presently have an orange shore-power lead that feeds down the hatch to a loose 13A domestic socket with a cheap domestic RCD plugged in, then to a loose 4-gang extension, into which I currently plug a C-TEK 7amp smart charger, plus whatever else is needed at the time (e.g. a small electric kettle, a small oil-filled heater, a fan-heater, laptop, phone-charger, hairdryer, etc).

All this crap of cables and trolling extensions needs to be put away before getting underway, it isn't properly safe, it isn't earthed or isolated, and there is no 240v ring-main to safely distribute power to fixed sockets around the boat. The 7amp smart charger should also really be upgraded to a 15amp unit for the size of my battery bank, and the old 300w modified sine-wave inverter upgraded to a modern 1000w unit before forming part of the ring-main.

Boat is normally kept on a mid-river mooring away from stray currents, has a wind-generator to keep the 2x110Ah domestic bank and the engine-start battery topped up, and the Beta 25 engine has a good 70Amp alternator fitted. The VSR ensures the engine start-battery on its completely independent circuit is always charged first, whatever the source.

So, aside from needing a water-proof flush socket to fit into a cockpit side-locker, an RCD to fit alongside the bigger charger and inverter down below, and cabling and domestic-sockets to run around the cabin, what else do I need? Do I need marine-grade cabling for the ring-main? Where do I earth the RCD to? Will I need to fit a galvanic-isolator and where in the system does this go?

Finally, what is so special about Marinco plugs and sockets - what's wrong with the cheaper normal blue/white kit (except that in rough weather my cockpit side-lockers can fill with green water)?

Cheers

Orange cable not suitable. Some is barely flexible on anything but a warm summer day.

Arctic cable, which remains flexible at low temps is commonly used, 2.5mm² being preferred over 1.5mm² but see https://www.google.co.uk/url?sa=t&r...TcDjYW4tlh9XDBNtxcGg1w&bvm=bv.125596728,d.ZGg
HO5 or HO7 cable is I believe preferred to so called arctic cable

Cant comment on Marinco connectors but note what pvb says about the gender of the connectors on the boat end of the lead and the inlet receptacle.

Consumer unit containing an RCD which protects everything and MCBs for each circuit. A "garage consumer unit" may suffice.
Galvanic isolator in the incoming earth connection advisable, Essential if you will be connected to shore power for prolonged periods.

A garage unit usually has a 6amp mcb which may be useful for a battery cahrger, and a 16 amp mcb which you can use for your sockets. A ring main is not essential, a radial system will be acceptable.
Use domestic flex for wiring , not twin and earth house wiring cable.

If you are going to wire in an inverter ( or generator) is t must be connected to the system with a suitable "transfer switch" which, as pvb indicates, prevents simultaneous connection of inverter and shorepower.

A portable generator can conveniently be plugged in via the shorepower connector.

All the details can be found in ISO 13297:2014 " Small craft -- Electrical systems -- Alternating current installations" and your installation should comply with its requirements. Beg, borrow or steal a copy !

 

[Yngmar]

The difference between the yellow Marinco and the blue/white IEC plugs is that the Marinco is waterproof (and the ones I've seen were all rated for 110V only, despite being used in 230V systems), while the IEC is only splashproof. Also the Marinco costs silly money. Furthermore there's now a waterproof version of the IEC plug, which brings its price nearer the Marinco range too (but at least it's rated for voltages this side of the pond). In all cases, the other end that plugs into the marina outlet is still only the splashproof IEC one anyways. In my experience, the splashproof IEC is totally sufficient, especially if you're planning to mount it in a cockpit locker (mine is mounted at the transom and has never given me any trouble).

The cabling is the same stuff used in houses, so stranded copper of appropriate dimension (1.5 or 2.5mm²). As it isn't tinned (I'm not sure tinned is even available), I'd advise to dip the ends into silicone grease and crimp bootlaces on and then dip those too before clamping them on for a good, durable connection in the presence of high humidity. Cables should be run inside flexible conduits which should be properly fastened so nothing can move when the boat is bouncing on the waves. Cables being able to swing around leads to rapid wear and failure.

Ring circuits were a uniquely British World War 2 cost-cutting measure and are not desirable.

Instead of an RCD and separate breaker, I suggest getting an RCBO, which is another abbreviation for an RCD that is also a breaker. This chap should be rated for 16A along with the rest of the system (unless you want to go up a plug size, but most marinas only have >16A connectors on berths for really big boats).

Clever trick from production boat builders: Get a short piece of DIN rail, saw it in half and drill holes near the end of each half, then bolt them back to back on some spacers behind a panel. This gives you a double DIN rail. On the front of it you slide the bits that need user operation (breakers, RCD, etc.) which you make panel cut-outs for and on the back the terminals for the wiring. Very space-saving and clean solution.

The Shorepower PE (protective earth - green/yellow) gets connected through to every part of the AC system, and to nothing else. You can get special yellow/green coloured PE terminals to slide on your DIN rail that use the metal rail itself for a PE, which is clever and convenient. If you don't connect the PE to anything else you will not need a galvanic isolator.

If you have an inverter or plan to fit one, you may also want to add a selector that lets you connect the AC outlets to the inverter (whilst disconnecting the shorepower - and the battery charger).

If you want to get fancy, throw in a cheap AC meter or even neater, a DIN rail version thereof. If not, at least add a control light so you can see when the AC is on. Preferably in a location you can see from a portlight or so without climbing back on and off the boat to see if the marina power is working now.

Add a switch to the battery charger so you can turn it off when you don't want charging but keep the rest of the AC system on (e.g. when working on batteries).

 

[Poignard]

Yngmar, that's a wonderfully comprehensive guide to what is required. I have the same lash-up as the OP and want to install a safe and tidy system. I'll follow your advice.

 

[VicS]

The Shorepower PE (protective earth - green/yellow) gets connected through to every part of the AC system, and to nothing else. You can get special yellow/green coloured PE terminals to slide on your DIN rail that use the metal rail itself for a PE, which is clever and convenient. If you don't connect the PE to anything else you will not need a galvanic isolator.

This suggestion does not comply with current recommendations and standards! It was a allowed by the obsolete ( 2001) edition of the ISO standard provided certain conditions were met.
It was something of an anomaly as it was not allowed in standards for other situations, caravan installations for example.

 

[nigelmercier]

The Shorepower PE (protective earth - green/yellow) gets connected through to every part of the AC system, and to nothing else...

Via a galvanic isolator.

As Vic has pointed out, this goes against current recommendations. However, sometimes common sense will prevail and the recommendations can be ignored. In a GRP boat, there is absolutely no reason for connecting the AC ground to the DC negative, and many reasons not to.

 

[rogerthebodger]

Via a galvanic isolator.

As Vic has pointed out, this goes against current recommendations. However, sometimes common sense will prevail and the recommendations can be ignored. In a GRP boat, there is absolutely no reason for connecting the AC ground to the DC negative, and many reasons not to.

100 % agree. There is also no need to connect the incoming earth to any anode and no need to link anodes together. This also eliminates the need for a Galvanic isolator.

This only applies to a GRP boat. Steel or Aluminium boats are very different.

 

[pvb]

There are valid safety reasons for earth bonding, which is why it's required by most organisations.

 

[SiteSurfer]

If it helps at all, I gleaned a lot of advice from this forum and building on virtually nothing did this:

A Safesure GI interupting the earth directly after the shore power plug in the cockpit.
Then the live/neutral/earth (from the GI) was installed to a Sentry MK IP65 Consumer Unit.
B&Q Artic Cable (I know probably not the reeeeally proper stuff but near enough) was used to wire one of the consumer unit outlets to 2 x double sockets and a weatherproof/waterproof socket in the battery locker.
More Artic Cable was used to wire the remaining outlet to an inline switch and onwards to the calorifier immersion element.

I have installed a Screwfix (£9) double USB & 240V socket for one of the outlets which makes life easier for the family when hooked up.

I then manually attach a battery charger to the outlet in the locker when I need it (I have a trickle charger and a beefy one for emergencies) which charges my batteries via the normal charging setup with the VSR and Solar Panel.

The consumer unit:

The GI:

B&Q Cable:

USB Outlet:

 

[Jabs]

Consider TLC Electrical. Much cheaper than most DIY shops and the chaps know what they are talking about!


Tony

 

[Babylon]

Yngmar, PVB, Vic, Nigel, et al - thanks so much for all of this.

Can't find a suitable low-profile flush IEP plug (yes aware of the gender difference here) for the very small open cockpit side-locker, so might spend a little more on either a waterproof Marinco or better still a Ratio 240v-rated unit:

The Shorepower PE (protective earth - green/yellow) gets connected through to every part of the AC system, and to nothing else... If you don't connect the PE to anything else you will not need a galvanic isolator.

As Vic has pointed out, this goes against current recommendations. However, sometimes common sense will prevail and the recommendations can be ignored. In a GRP boat, there is absolutely no reason for connecting the AC ground to the DC negative, and many reasons not to.

100 % agree. There is also no need to connect the incoming earth to any anode and no need to link anodes together. This also eliminates the need for a Galvanic isolator.

There are valid safety reasons for earth bonding, which is why it's required by most organisations.

Surely the purpose of bonding the AC earth to the DC negative (the engine negative or direct to the hull anode?) is to provide redundancy in case the earth on any given 240v shore-side supply is corrupted?

Yes, plan to fit a 240v selector switch to ensure that only either the shore-power or the inverter (which also has its own on/off switch) can supply to the (radial-wired) sockets at any time. Is a socket-output on the inverter supply such as this one adequate, or should I find a 1000W inverter that can be hard-wired out?:



The 15amp smart battery charger also switches on/off and has selectable modes (charge/supply/recondition/silent):



Both these units and the selectable switch will be positioned for easy access and vision above the battery compartment.

I have very limited wriggle-room for running cabling to the 240 sockets in the cabin: some will go under headlining and behind panels, but will properly secure these and use protective conduit for exposed areas elsewhere.

 

[nigelmercier]

... Surely the purpose of bonding the AC earth to the DC negative (the engine negative or direct to the hull anode?) is to provide redundancy in case the earth on any given 240v shore-side supply is corrupted? ...

Almost exactly the opposite. It is to prevent a fault from electrifying the metalwork or the water around the boat. With modern equipment this is almost impossible, hence the recommendation being nonsense. I suspect it originated in the US, where they do things differently.

 

[rogerthebodger]

Almost exactly the opposite. It is to prevent a fault from electrifying the metalwork or the water around the boat. With modern equipment this is almost impossible, hence the recommendation being nonsense. I suspect it originated in the US, where they do things differently.

I also think land based installation specs also have on influence. Land based installations are also different to marine GRP setups.

 

[rogerthebodger]

There are valid safety reasons for earth bonding, which is why it's required by most organisations.

I have been through an analysis several times and to date no one has been able to repudiate my analysis except by quotation published standards and organisations with vested interests.

 

[rogerthebodger]

Surely the purpose of bonding the AC earth to the DC negative (the engine negative or direct to the hull anode?) is to provide redundancy in case the earth on any given 240v shore-side supply is corrupted?

I would much rather have a means of ensuring that the primary earth is not corrupted and not have to rely on a rather hit and miss alternate path through the hull fittings water and unknown ground spike.

This can be done very easy by fitting 2 neon indicator lights one between line and earth and one between neutral and earth. This would also indicate and reverse phase connection.

 

[Aurai]

Requirements for Electrical Installations, even on boats do not need to be over complicated but a trained mind and familiarity with the IET Wiring Regulations will give you an approach towards a safe installation. Given that Screwfix and Co will provide a "Garage Unit" and that is all an electrician would supply, you are halfway there. Even if you do not know why.

The unit provides basic protection through basic insulation of live parts, barriers and an enclosure.

Fault protection by protective earthing, bonding and automatic disconnection. On a boat and shore power you are relying on the protective earthing back along the cable to the supply pillar. Then you need a protective device that automatically interrupts supply in the event of a fault condition, within tabulated times in the regs. Your MCB will provide this protection.

An RCD provides additional protection and is included in the garage unit.

Now all you need are the cable, and sockets chosen carefully, and professionally terminated. We have the Marinco fitting in the cockpit with the water protective over boot and its sturdy feel is always reassuring.

When I go and "fix" friends boats it is usually the connections that have been very poorly finished not the selection of kit.

Cheers

 

[nigelmercier]

One thing to add. Most mains distribution gear will expect solid cable, which you must not use. It is worthwhile getting a bootlace ferrule crimping tool and some bootlace crimps to finish the wire ends.

 

[davidpbo]

I have just bought a small consumer with Wylex 16A 10ma RCCD on ebay for possible use on my boat. I hope that is not too tight a protection given the leakage on some switch mode psu gear. 10ma is I believe the recommended trip leakage current for agricultural buildings which are another wet environment but generally 10ma RCCDS are a lot more expensive. This one was not.

I think the spec. for an RCCD is that it should not trip at less than half its rated (leakage current) but must trip in a certain time at the rated current.

My thinking is that that protects the incoming cable and if I wire to the sockets in 2.5mm will protect those as well. If I use 1.5mm I will probably sub fuse to 10A.