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Installing shore power


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Hi,
 

Recently my sister bought a boat and she asked if I could look over the onboard electrics which have two double sockets and a water heate. These are fed from the onshore power.
 

I have determined that the power inlet at the side of the boat is European. For safety the live and neutral on the inlet connector are backed up by two glass 10 amp fuses. The 2.5 cable coming from this inlet has a European plug attached to the end of the cable. It has the two prongs, which are live and neutral with the earth built into the plug.

This plug then plugs into a European triple socket. This triple socket has a European to UK adapter plugged into it. Plugged into this adapter is a three pin plug powering the water heater. Coming out of the triple socket is another European plug which feeds two double uk sockets.

As you can clearly see this is a very dangerous setup not to mention a health and safety hazard and a fire risk. This wiring configuration could also cause reverse polarity on the live and neutral if you plug in the European plug incorrectly I cannot see any bonding from this arrangement to either the engine block or the negative terminal on the battery.

The boat is being currently fed from shore power by a 20 amb rcbo.  I have some knowledge of electrics so sister asked could I rewire the boat and install a galvanic isolator. 
 

I was planning on putting in a consumer unit with  20 amp and 16 amp mcbs.  Alternatively someone has suggested installing individual RCBOs.

 

The biggest issue I have is determining what I need to use for my mains breaker if I was to use either Mcb or rcbos.

 

My other query is peoples thoughts on attaching the onshore earth to the negative on the battery.

I just wanted to reach out and get other peoples opinion. I wanted to see if the was something other boaters may have tackled themselves or left to the professionals.

Thanks 

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From what I can gather providing the cable  type and sizes meet UK requirements you could change the shoreline connectors for the UK standard and wire the boat side to conventional "garage" consumer unit with RCD & MCBs or RCBOs. The consumer unit may well have its own isolation switch.

 

The incoming earth ideally needs an isolation transformer or a galvanic isolator in it to prevent hull corrosion if its  a metal boat.

 

The mains earth would ideally be connected by suitably coloured and sized able to a point adjacent to the 12V hull bond, usually on an engine bed. If you connect it to the battery negative or the DC hull bond then there is the theoretical possibility of the 12v system being fed 240VAC under fault conditions, so best not to do it.

 

Your question about the mains earth to the battery negative suggest that you might not have the knowledge to do this safely. Remember, mains can and dies kill.

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21 minutes ago, Ali553 said:

My other query is peoples thoughts on attaching the onshore earth to the negative on the battery.

 

 

That sounds like a nightmare but I'd suggest that it is not good practice to connect the 230v AC earth to the 12v DC battery negative.

 

Reading your description it sounds as if it is not a convention electrical system but a 'rats nest' of extension leads and adapters - is it ?

 

If rewiring then be aware that 'domestic' (such as T&E) cables are not advisable for use on boats.

 

Maybe a look at the ISO specifications for "small boats wiring" would be a good place to start.

ISO 10133 is the Low Voltage DC and ISO 13297 is the specification for AC systems The two specifications are being combined but as far as I know it has not yet been released.

 

What sort of boat is it ?

If it has come from Europe then presumably it was (is) RCD compliant.

Where are you planning to use it ?

 

If it is a boat that you intend to use on the canals will it meet the various requirements of the Navigation Authority (Typically the Boat safety Scheme) which cover all aspects of electricity, gas, fuel etc etc, and compliance (on most waterways) is mandatory before you can get the boat licenced.

 

If you want to provide more information the folks here are very experienced and will be able to guide you as to waht you need to do.

Edited by Alan de Enfield
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55 minutes ago, Ali553 said:

The 2.5 cable coming from this inlet has a European plug attached to the end of the cable. It has the two prongs, which are live and neutral with the earth built into the plug.

Do you really mean a plug I.e. something with brass pins sticking out? Or do you mean a line socket? A plug in this situation is highly dangerous in that if it is unplugged while the rest of the shore power is connected there will be live bare metal pins with mains voltage on them. This could kill!

 

The whole thing sounds like a dangerous mix installed by someone who had no sense of what is needed. Your sister should be advised not to plug into the shore power bollard until it has been properly sorted out.

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Hi. 
 

Many thanks for your reply.

 

yes I felt it was not a good idea to attach the onshore earth to the negative on the battery.

 

Your correct with your description of the wiring layout on the boat. Whoever previously did it created a diy disaster and I feel it’s is not compliant.

 

Its a cruiser which will require work make it compliant hence why the Buddhist job will be the electrics

 

 

 

 

 

David,

 

it’s a European plug and which has two brass prongs/pins sticking out. Yes this is a very dangerous setup where someone could get electrified if they plugged it out and touched the pins 

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4 minutes ago, Ali553 said:

it’s a European plug and which has two brass prongs/pins sticking out. Yes this is a very dangerous setup where someone could get electrified if they plugged it out and touched the pins 

 

This is extremely dangerous and I'd disable the system until it can be sorted. (by disconnecting the wiring at the shore line socket) This type of arrangement is sometimes used by cowboys to connect a generator to a house ring main......referred to as a suicide plug for obvious reasons. 

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I would install just one MCB rated at 16A, which is the rating of the normal shore power connectors used in U.K. inland boating. If you install multiple MCBs that add up to more than 16A then one can overload the connector and cable without anything tripping on the boat. Whether you want to have one 16A MCB and one RCD, or one 16A RCBO is a matter of opinion. We just have the one 16A RCBO which keeps it simple!

 

Plus of course a galvanic isolator inserted into the incoming shore earth.

 

And a bonding wire from the RCBO/consumer unit or whatever earth, to a hull stud. Of course if it’s plastic cruiser then no point in earthing the hull, but maybe just any interconnected metalwork such as engine/transmission and any exposed copper pipes.

Edited by nicknorman
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Nick,

 

Thanks for the reply.

 

you say you have only one 16 A rcbo but I was going to put in either three, mcb or rcbo, one for sockets, one for the water heater and one for lights.  

Correct me if I am wrong but I thought you needed an rcd to backup the mcb?

 

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6 minutes ago, nicknorman said:

I would install just one MCB rated at 16A, which is the rating of the normal shore power connectors used in U.K. inland boating. If you install multiple MCBs that add up to more than 16A then one can overload the connector and cable without anything tripping on the boat. Whether you want to have one 16A MCB and one RCD, or one 16A RCBO is a matter of opinion. We just have the one 16A RCBO which keeps it simple!

 

Plus of course a galvanic isolator inserted into the incoming shore earth.

 

And a bonding wire from the RCBO/consumer unit or whatever earth, to a hull stud. Of course if it’s plastic cruiser then no point in earthing the hull, but maybe just any interconnected metalwork such as engine/transmission and any exposed copper pipes.

 

Bonding on a plastic boat - to any metal a person may come into contact with so metal sinks, basins, taps and metal shower parts if plumbed in plastic.

Edited by Tony Brooks
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Tony,

 

I recently picked up a Sterling Pro Save A Galavanic Isolator.

 

The wiring diagram for this unit shows the earth from the consumer unit on the boat connected to the earths bonding system of which it shows the negative on the battery terminal 

 

 

 

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I have given you the best advice I can, so you choose who you will believe. So far I note that none of the other members with electrical knowledge has contradicted me, but there is yet time.

 

If, for some reason, the DC bod point becomes detached you will not know unless you get a DC fault, but the DC MCB/fuse will not trip with no bond. Then if you get an AC fault the whole 12V system may well become live at mains potential. In your case, it may not be as potentially dangerous as it would be on a metal boat but it's a risk I would not take.

Edited by Tony Brooks
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10 minutes ago, Ali553 said:

Tony,

 

I recently picked up a Sterling Pro Save A Galavanic Isolator.

 

The wiring diagram for this unit shows the earth from the consumer unit on the boat connected to the earths bonding system of which it shows the negative on the battery terminal 

 

No this is not the right way to do it. Yes it will work, but it is not fault proof. The way to wire up boats for AC and DC wiring is defined by the relevant BS ISO standards. These specify connecting the 12v negative and the mains earth to separate but adjacent points on the hull (or whatever the main lump of metal is, maybe the engine). As Tony says, connecting to the battery negative introduces the possibility of that becoming disconnected from the hull whilst leaving it connected to 12v appliances which creates a remote possibility of mains voltages on 12v appliances.

 

I’ll agree that the risk is fairly small, but why not just do it the right way in the first place!

1 hour ago, Ali553 said:

Tony,

 

Regarding your single mcbo, are you using a double pole switch ?

Nick maybe? Yes it is a double pole RCBO.

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1 hour ago, Ali553 said:

Nick,

 

Thanks for the reply.

 

you say you have only one 16 A rcbo but I was going to put in either three, mcb or rcbo, one for sockets, one for the water heater and one for lights.  

Correct me if I am wrong but I thought you needed an rcd to backup the mcb?

 

This is “house wiring thinking”. In a house, lighting is not usually protected by an RCD and the current is fairly small (6A breaker and thin wiring). In a boat, everything should be protected by an RCD. But does this boat actually have built-in mains lighting? I don’t mean eg table lights plugged into a 13A socket. That is fairly unusual and if it does then the circuit (wiring) should be protected by a breaker of less than the cable rating and that makes it hard to limit the overall current to 16A without having another 16A MCB feeding the rest of them.

 

What is the reason for wanting a separate breaker for the water heater? Again in a house, the incoming current capability is huge, there is a huge master fuse. And typically a ring main or two with 32A breakers and a separate breaker for the immersion heater, shower etc. But in a boat as I said the max current is limited to 16A. If you turn on appliances including the water heater, so as to exceed a total of 16A, you want something on the boat to trip, rather than relying on someone else’s shore bollard breaker, if you don’t want a catastrophe caused by the shore cable melting.

The easiest way to achieve all that is to use one 16A breaker (MCB+RCD, or RCBO) to feed everything, unless there is a good reason to do something different.

  • Greenie 1
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Nick,

 

The main reason to wanting the lights, sockets and water heater on separate circuits was in case a fault was to happen on any of these circuits.

 

I understand that and know that the maximum amps I can pull is 16. My theory was that if my sister plugged in her 2kw owen and a kettle at the same time which was to turn exceed 16 amps,  I wanted that 16 amp circuit to trip and not the shore power rcbo.

 

Recently she plugged in her oven then switched on the water heater and blew the 10 amp glass fuse that is in the power inlet connector at the side of the boat

 

 

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I really think that your sister should reappraise what a boat can support - electric water heater, electric oven etc etc. is not viable. unless the whole boat system is capab;e of supporting it.

 

From you questions and answers I'm not sure that you have the experience of boat system to be able to undertake a safe installation.

As I said very early on, you cannot transplant domestic wiring practices to boats and need to read, learn and apply the correct ISO requirements, or employ a suitable person with boat wiring experience.

 

Water and 230v do not good bedfellows make.

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16 hours ago, Ali553 said:

Tony,

 

I recently picked up a Sterling Pro Save A Galavanic Isolator.

 

The wiring diagram for this unit shows the earth from the consumer unit on the boat connected to the earths bonding system of which it shows the negative on the battery terminal 

 

 

 

Ignoring for a moment the option of using an isolating transformer, the shore Earth (either direct or via a galvanic isolator) must connect to the boat hull - assuming it is a metal boat.  Additionally the negative pole of the 12v system is also required to be bonded to the hull.  Ideally the 240v AC Earth connection and the 12v negative should be connected to the hull by separate studs that are adjacent.  This is all defined in the iso standard mentioned earlier.

 

Added - Failure to connect Earth bonding wires for shore power supplies correctly can under certain fault conditions result in the boat being ‘live’ and if touched by someone standing on the bank/pontoon etc result in a fatal electric shock.  Whilst the risk of this is greatly reduced as most supplies are RCD protected it is not wise to rely on that rather than doing the job properly.

Edited by Chewbacka
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Thanks for that.

 

Not owning a boat but am familiar with electrics, I was not aware up until this forum there are ISO standards.

 

I have a brief look at them last night on my phone but really need to review them on my laptop with a bigger screen.

 

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1 minute ago, Ali553 said:

Thanks for that.

 

Not owning a boat but am familiar with electrics, I was not aware up until this forum there are ISO standards.

 

I have a brief look at them last night on my phone but really need to review them on my laptop with a bigger screen.

 

 

The suggestions you are getting are varied, and much depends on the material the boat is manufactured from - is it :

Steel

GRP (Fibreglass)

Wood

Ferro Concrete

 

Not only are there ISO standards, but there are BSS (Boat Safety Standards) that the boat must achieve to be able to get a licence.

Where is your sister planning on floating / using this boat ?

 

Just like your car you need a

BSS (same as the car MOT)

Insurance

Licence (same as the car 'road-tax')

 

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Alan,

 

The hull is steel and she was thinking Of using it on the Thames up past Windsor.
 

The  boat needs additional work done to it so I have recommended to her to get it booked in for a full  MOT.  

 

 

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