240 volt Wiring

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ColinS

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What type of wire should I use for a ring main in a motor boat?
My new purchase has 'flex' type wire (multi-strand), probably 1.5mm section (too small, I know it should be 2.5mm). Should this be upgraded to 'twin & earth' flat (house wiring) or would the engine vibrations be detrimental to the single cores, even with secure wire clamps.
Any comments gratefully received.
 
Well if it's any comfort, our boat has flat twin and earth throughout for the mains cables, a 1988 boat so hardly un-tested, with no age related mains electrical problems.

If I'm honest I don't know if the latest Regs (or BSS requirements) require anything different, but I can't see why FT&E wouldn't be perfectly safe in any event. Might be worth referring to the BSS for guidance to be sure.

You make a good point about vibration; the only areas likely to be a concern are in the fittings, where you need to make sure all the screws are done up tight, and any stray / loose / expansion loops where the cable might flop around. As you say, just clip it well.

That's my two penneth anyway! Hope it helps.
 
Flex is always recommended to withstand the vibration.

For marine use tinned wire should be used rather than ordinary domestic stuff.

1.5mm² is Ok provided you do not want to exceed 3 kW load AND the fuse/mcb in the distribution board is only 15 amps, but as you say 2.5mm² would be better.
 
ColinS said:
What type of wire should I use for a ring main in a motor boat?
My new purchase has 'flex' type wire (multi-strand), probably 1.5mm section (too small, I know it should be 2.5mm). Should this be upgraded to 'twin & earth' flat (house wiring) or would the engine vibrations be detrimental to the single cores, even with secure wire clamps.
Any comments gratefully received.
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Yup I'd second VicS - flex for vibration reasons. Tinned is pukka, but v expensive and questionable whether you need it unless you're a perfectionist

FWIW my new Fairline is all flex, 1.5 and 2.5mm depending on the circuit, and not tinned

It's worth remembering the need for utmost care, because a fault can mean a desparate fire. Many of the boat fires seem to be electrical. On my last boat BA Peters installed a 230v item with atrocious wiring, and this caused a tiny localised fire at a terminal block. I happened to catch right away, but it taught me a lesson!
 
Thanks for the help all.
I think I will go for flex 2.5mm based upon the ease of installing over Twin & Earth, and the fact that new boats appear to be built that way.
 
It might be worth checking the Boat Safety Scheme website. It will have a recommendation for wiring, and worth considering if the boat is ever to be used on a river.
 
Over the years BSS have made pronouncements on many matters, some of which were effectively impracticable. After much haranguing (?sp) these got changed back to something more practical.

This is one of the reasons many folk pour scorn in it. The trend now is to make a vague rule and leave the inspectors to sort it out. The trouble is newer inspectors don't have to have any practical boaty knowledge.
Doesn't hurt to look at what they say, though.

For a self install you'll probably be using domestic sockets, the catch here is that these are designed to be used with solid conductors only and flat T&E as well. Thus you have an immediate mismatch.

I'm sure the IEE regulations take a dim view of the mix.

So as usual the individual is damned if you do damned if you don't, there's no way you can find out what best practice is, you'll have to use your own judgement.

I said a rude word (or series thereof) and used round flex with standard best quality switch sockets. Round flex goes round corners easier and has more resilience than flat. I took more care withe socket entry cutouts, and made sure there was plenty of "meat" in the screw terminals.
I could have used separate flex strands, but the 3-core cable stands out from my low voltage wiring which runs in the same space.
 
ColinS said:
Thanks for the help all.
I think I will go for flex 2.5mm based upon the ease of installing over Twin & Earth, and the fact that new boats appear to be built that way.
Click to expand...

I am not sure what the term "flex " means to you,
is it single flexible wires, or 3 wire flexible cable ?

FWIW,
for mobile applications, in my boat, aswell at the company in mobile Outside Broadcast Cars, we alway's use 3 wire flexible cable, for 230V, like the power lead on your water cooker.

this gives a "double" isolation of the 230V wires, and extra protection to damage by vibration,
and in the boat you can easyly distingiush these cables from the single wire, low voltage DC cabling.

agree as some have said on here, the termination of wires is extremely important, to avoid fire,
potential sparks is one of the main sources of fire, especially in vibrating places, but also in domestic installation.
 
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240v wiring

When rewiring the domestic electrics on my boat I did some research on suitability and sizing etc of cables and fittings for safety, durability and compliance with IEE regs & BSS, as my wiring runs through the engine compartment. Coming to the conclusion that for the socket outlets the best way was to wire in a ring circuit choosing 2.5mm 90*c thermoplastic insulated flex, or in English ask your local electrical wholesaler for 2.5mm immersion heater flex.
The terminals in domestic sockets are suitable for this cable.
All backed up by an RCD main switch.
Unfortunately being an electrician with 26yrs experience and qualifying supervisor for niceic gives me an unfair advantage.
Hope this helps, pm for more boring info if you get stuck.

Chris
 
A supplementary question.....If the boats shorepower socket (ie what you plug the trailing lead into) is rated at 16 amps, should the main protective breaker on the boat also be rated at 16 amps?
 
Thanks again all for the continued list of suggestions.

My reference to flex was the 3 core mains type, not single wires.
I was planning on using cable ferrules (not to be mistaken for crimp connectors) because it is stranded wire, which make a solid termination for the screw terminals to bite on (I use these in my other life working in the electronics industry).
The idea of using the higher heat rated cable for immersion heaters et al seems a fine idea.

One final question:- Should I run the flex cables in PVC flexible conduit for further segregation? I know that I can get some with 15mm bore, which with a bit of effort should accomodate 2 cables as part of my ring main. Or is this just OTT?
 
mrgrumpy2 said:
A supplementary question.....If the boats shorepower socket (ie what you plug the trailing lead into) is rated at 16 amps, should the main protective breaker on the boat also be rated at 16 amps?
Click to expand...
it should not be rated any higher (but it could be lower)
 
240v wiring

I fitted the following,
Main switch on boat 16amp rcd
Lighting circuit wired in 1mm flex protected by 6amp breaker.
Ring circuit wired in 2.5mm heat resist flex protected by 16amp breaker
1kw immersion heater wired in 1.5mm heat resist flex protected by 6amp breaker.
Battery charger wired in 1.5mm flex protected by 6amp breaker.
The ends of the wires (the terminations) were fitted with "bootlace ferrules.
All cables are fixed where accessible at regular intervals using "P" clips and stainless self tapping screws and suitable bushes used at entry points into accessories and through bulkheads.
Where cables could not be hidden self adhesive pvc trunking (YT1 or YT2) was used.
Wherever possible mains and 12volt wiring are segregated as in wiring regs 515.2 & 528.1 etc.
Using this system I have short circuit protection for the whole boat and overload protection for each circuit. Although boats are not mentioned directly in the wiring regs (marinas are) and it took a bit longer to install the wiring meets the requirements of wiring regs and the BSS inspector was impressed with the installation.
 
Are there any particular brands of RCD's that I should be considering for installation and use within a marine environment?
 
I like round flex, for the simple reason that I can seal fittings inside airtight boxes. My "penetration" into the engine room is below the water line and I needed to retain water tight bulkhead, as I am refitting an old (late seventies) boat and needed three water tight bulk heads to get around having to do a practical flotation and stability test. Flat cable would have been a pain to seal, though not impossible. Luckily in South Africa, they have a domestic shielded cable which is round not flat and has an insulated earth. My older boat has cabling installed in a commercial yard to the then (1968) commercial standard of cotton coated solid wire, which I will replace.

Robin
 
240v Ring main installation

I have found that older installations exhibit some green oxidisation on any copper cable exposed and inside boxes too, also I have found it necessary to strip cables back to remake better and more conductive joints because of this. So you may consider using an inert gel or say a vaseline type to impregnated the cable casing ends ( work it up the cable shearhing) and to "heat shrink " (sheathing) the individual cable ends, I`m not sure of anything that can be put on the actual terminals but I have no doubt that there is a proprietry make available, maybe a mastic applied locally will do. I would prefer a round flex with an individually insulated earth, rather than flat 2.5 without. IMHO hope that helps
Rob
 
I have found that older installations exhibit some green oxidisation on any copper cable exposed and inside boxes too
Click to expand...
Thats why tinned cables are recommended for marine use!

Can you use the Garage type consumer unit/RCD which is sold with a 16A and 6A mcb?
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Yes if 1 x 16amp and 1x 6amp suits your proposed use. Available dust and waterproof to IP65 from Screwfix for about £40 (May not include cable glands)

Basic from Merlin Powerstore is 2x 16amp, dust and water proof to IP55, costs nearly £90 with glands, grommets etc
 
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