Extending a 230 volt circuit (on a boat)

[Quandary]

My boat came with a Navix shore power box in the cockpit locker, this has some circuit breakers and a multi stage battery charger. It is claimed to include a galvanic isolator also but as I can not read Finnish I have been unable to fully verify that. The 230 volt output goes to three continental type two pin sockets, one on the other side of the bulkhead is for the immersion heater and there is another one in the locker in the heads and the third is above the chart table. The immersion heater is rarely used as we are not marina based and the engine heats the water fairly quickly when we are on the move, the one in the heads is never used except occasionally for charging mobile phones or cameras, but my wife plugs in an electric kettle to the chart table plug which has an adapter for 3 pin plugs. When in use the kettle sits on the chart table which is an unwarranted use of a hallowed space, I would not permit this invasion if I did not like coffee so much.
My plan for this winter is to fit a 13 amp domestic switched plug (perhaps even a double?) on the other side of the boat above the galley worktop, I propose to use some heavy flex to wire it via the bilges (shore power cable). Is there a safety issue here, there must be a reason why Finngulf did not put a plug at the galley?
Do I need to wire it right back to the switch box or can I spur it off from the never used one in the heads, should I use 3 core cable for this and if so where would the earth wire go, I presume there is no earth in the existing plugs.
I had also considered adding another plug to allow a small ( less than 500w.) heater to be fitted under the table occasionally, if there are two are they better on a little ring main.
Or would I just leave it all alone and continue to share the chart table?

 

[dt4134]

I did a wee bit of rewiring of my boat, mainly because the previous owner had badly bodged a few bits and pieces so I really thought I ought to re-introduce the RCD into the circuit (actually I ended up replacing it with an RCBO).

Do Finnish-style continental plugs not have an earth? German ones have it around the rim and the French have a male connector on the socket and a female connector on the plug. All the original German wiring on my boat was 3-core.

You could fit a UK socket (if that's not your plan already). I did, but I was lucky that there was a box behind so there was no risk of the back of the socket being exposed to contact (obviously something you should watch out for).

Spurs are a bad idea in domestic wiring, but my boat already had spurs and anyway I led the new wiring back to the junction box where the RCD was.

Ideally you should go back to your shorepower unit. But...hazarding a guess... does it have a circuit breaker on each connection and are there only three?

In which case if you do add a spur you have to make sure the wiring can cope with more current than the circuit breaker, which it should already, and accept that if you put a heavy load on both at the same time it'll trip.

My wiring doesn't get right down into the bilges and where it crosses the boat it does so on top of a rib. Interestingly the original wiring, most of which is still in place, was all three-core mains cable with tinned wire. Obviously German made with, IIRC, a DIN number.

By the way, I've just fitted a galvanic isolator. Came with a monster heatsink, so if you have one fitted you should be able to spot that.

 

[Stork_III]

Are your outlets "Berker". If so they do have earth to spring clip inside socket. UK 3 pin insert replacements are available from here http://www.abcomponents.co.uk/socket_outlets.html

 

[fireball]

My plan for this winter is to fit a 13 amp domestic switched plug (perhaps even a double?) on the other side of the boat above the galley worktop, I propose to use some heavy flex to wire it via the bilges (shore power cable). Is there a safety issue here, there must be a reason why Finngulf did not put a plug at the galley?
Do I need to wire it right back to the switch box or can I spur it off from the never used one in the heads, should I use 3 core cable for this and if so where would the earth wire go, I presume there is no earth in the existing plugs.
I had also considered adding another plug to allow a small ( less than 500w.) heater to be fitted under the table occasionally, if there are two are they better on a little ring main.
Or would I just leave it all alone and continue to share the chart table?

The answer is "it depends" ...

Your system is limited by the supply - so if you're on a standard 16amp shore power cable a 30amp ring main isn't going to be tested to it's limits and would be overkill - although there is some merit in overspeccing that part ...

Basically - 16 amps =~3kw - so any socket you put in now should be able to deliver ALL 16amps to whatever appliance you plug in - we have a 2kw electric radiator that can plug in anywhere - other appliances are the toaster, kettle and an electric grill. Obviously you can't have it all on at once (not for long anyway!).

So - the question as to whether you should spur or not rather depends on the cable size running to the point where you are spurring from - if it is sized sufficiently the there will be no (or few) issues.

We had a low level socket (why?!) in the galley that was inconvenient for any galley appliance - so spurred off this one to a double at counter level.
We do plug the heater into the low socket - but as it is 2kw and the kettle is ~1kw we tend to turn the heater off whilst we boil the kettle.

If you do run a light weight cable through it should be on a breaker that cuts out before it reaches the capacity of the cable - you don't want to be putting a 2kw heater through a 5amp cable!

 

[lenseman]

As an aside, you can translate basic Finnish by using Google.com as there is a Translate facility if you tab on the 'more' tab then enter the Finnish in the first box

 

[DJE]

At least you are still allowed to install a new socket yourself on the boat. If this was in you kitchen at home in the UK you would need building control permission and/or to get the work done by an electrician.

 

[Barry Jones]

You don't mention whether the shore power box has an RCD fitted or not - I presume not.

I wouldn't be happy using appliances that aren't double insulated on two pin sockets.

In a galley I normally fit a 10mA RCD as per the BMEA guidelines.

Also, I wouldn't run mains cables anywhere near the bilge.

My boat came with a Navix shore power box in the cockpit locker, this has some circuit breakers and a multi stage battery charger. It is claimed to include a galvanic isolator also but as I can not read Finnish I have been unable to fully verify that. The 230 volt output goes to three continental type two pin sockets, one on the other side of the bulkhead is for the immersion heater and there is another one in the locker in the heads and the third is above the chart table. The immersion heater is rarely used as we are not marina based and the engine heats the water fairly quickly when we are on the move, the one in the heads is never used except occasionally for charging mobile phones or cameras, but my wife plugs in an electric kettle to the chart table plug which has an adapter for 3 pin plugs. When in use the kettle sits on the chart table which is an unwarranted use of a hallowed space, I would not permit this invasion if I did not like coffee so much.
My plan for this winter is to fit a 13 amp domestic switched plug (perhaps even a double?) on the other side of the boat above the galley worktop, I propose to use some heavy flex to wire it via the bilges (shore power cable). Is there a safety issue here, there must be a reason why Finngulf did not put a plug at the galley?
Do I need to wire it right back to the switch box or can I spur it off from the never used one in the heads, should I use 3 core cable for this and if so where would the earth wire go, I presume there is no earth in the existing plugs.
I had also considered adding another plug to allow a small ( less than 500w.) heater to be fitted under the table occasionally, if there are two are they better on a little ring main.
Or would I just leave it all alone and continue to share the chart table?

 

[Quandary]

Thanks for all the useful responses.
BTW The boat has a sail drive so so far in 5 years the bilge cavities have been a bit dusty but never wet. If I clip the flex close to the top of one the transverse beams it will be a lot drier than the bit of the same stuff that runs from the pontoon to the plug in the cockpit.

 

[rotrax]

At least you are still allowed to install a new socket yourself on the boat. If this was in you kitchen at home in the UK you would need building control permission and/or to get the work done by an electrician.

Hi, just read the link and,as I suspected fitting a socket in your kitchen is " non notifiable" so its OK for a competent DIY'er to get on with it!

 

[DJE]

Hi, just read the link and,as I suspected fitting a socket in your kitchen is " non notifiable" so its OK for a competent DIY'er to get on with it!

That's not how I read it:-

In addition, some other works may be deemed Non-notifiable anywhere except in kichens, bathrooms, utility rooms and other special locations. In these areas they will be considered Notifiable
Examples of such work are:
Adding light fittings and switches to existing circuits
Adding sockets or fused spurs to existing ring or radial circuits

The OP was talking about adding a spur.

 

[prv]

Hi, just read the link and,as I suspected fitting a socket in your kitchen is " non notifiable" so its OK for a competent DIY'er to get on with it!

That link is a bit vague.

My understanding (albeit it's a few years since I read the regs) is that while adding a spur socket would be OK in most of the house, in the kitchen most things are notifiable except for like-for-like replacement.

However I also believe that most BCOs have no desire to get involved in domestic wiring and didn't want these regulations foisted on them, and that the number of electrics-only DIY jobs that get notified is small to non-existent.

Pete

 

[ProDave]

the one in the heads is never used except occasionally for charging mobile phones or cameras,

By far the simplest thing would be to re route the unwanted socket in the heads to the other side of the boat and feed the new socket from that.

It would be much much better to install a completely new run of cable right from the fuse box to the new socket, just remove the old cable and connect the new one to exactly the same place. That would be much better than jointing 2 cables with a junction box.

While you are at it, change all the continental sockets for 13A sockets to make life much easier.