240 volt Wiring

There are a couple of other factors that you may need to consider when selecting a cable size: grouping of circuits, thermal insulation and if the cables run through a hot area.

All of the above can reduce the current carrying capacity of a cable. You also need to consider the length of run of course.

If you install a 16A RCD or Fuse, the type of device fitted (time/current characteristics) will also influence the maximum recommended current carrying capacity of the circuit cabling.

So, I would probably go for 2.5mm2 tinned stranded cable, as has been said, to avoid corrosion issues, it is also better particularly where the loom could move.

Making the circuit a ring increases the current carrying capacity of the primary conductors in that circuit.

On most boats you could probably use a 1.5mm2 ring with no problems at all, the circuit length is usually short; but if I were installing this circuit on my boat, I would certainly go for 2.5mm2. The cost diffecerence is not too significant and the volt drop across the cable will be less.

When taking a cable from the main RCD on a boat, it must of course be rated to carry the maximum current of all installed loads, this size of cable must run to the input side of all breakers/fuses before they drop down to serve circuits with a lesser rated breaker/fuse and cable size.

All clear as mud!
 
There is only one way to do the job properly and that is to use Piro with the proper sealed switches, sockets and plugs.
Totally Fire and water proof, submersible too.
Damed expensive and I would really only consider it on a live aboard.

Yes indeed I do mean Pyro sorry gents for the typo.
It is good and will survive for an extremely long time if installed and made up properly.
 
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one way to do the job properly and that is to use Piro
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Piro ??

You mean "Pyro" ... short for Pyrotenax. One brand of mineral insulated (MI) cable.

Can be a PITA in damp conditions though when the sealing starts to deteriorate.
 
VicS said:
Piro ??

You mean "Pyro" ... short for Pyrotenax. One brand of mineral insulated (MI) cable.

Can be a PITA in damp conditions though when the sealing starts to deteriorate.
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Hear, hear. I don't think it likes vibration either. After all - crudely put, it's a bit like Gyproc wall board; clay surrounded by a container - if you see what I mean.

I wired my boat with surplus Def-Stan cable from HM dockyard Portsmouth.
- na-na-di-na, just hoping it isn't the stuff that caught fire in the Falklands...

On a sensible topic there's a chap (on a satellite forum) who swears by silicone grease, says it's like snake oil, us it for anything. A latter day Vaseline, perhaps, but it doesn't dry out.
 
If you have a cross channel ferry, then MI cable might be OK for say fire alarms but it certainly should not be used for a ring main on a small FG boat. Its a pain to make off the glands/ends (which should be done in a dry environment), and any vibration could cause problems with glands and when they do occur, it would be a pain to rectify them. Also much more inflexible.

For a ring main on a boat, you want what has already been suggested, good quality tinned copper stranded cable, perfectly fit for purpose and a fraction of the cost compared with Mineral Insulated cable!

Roll on the summer.....

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Tinned copper mains cable is not easy to find and when you do find it, it is expensive. Much of it is rubber sheathed as well and whilst it's great for power tool leads etc, the rubber may not fair well long term in a marine environment.

I'm not that convinced that cable has to be tinned, certianly nice but I don't think it's essential unless you think it's going to get wet. I have standard copper cable on my boat that's over thirty years old and much of it's still fine.

I used 2.5mm "Arctic" cable which is easily available and relatively cheap, try Screwfix. You do need the bootlace ferruls though and a suitable crimping tool. You could get those from RS Components.
 
Yep, I can agree with that, tinned IMO better but most certainly not MI!

There is also a fair argument to be had regarding twin and earth - stranded better as its more flexible but can cause problems when terminating, solid T&E is cheap and in most cases would do OK!
 
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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Don't use twin and earth or any single stranded wire. If it's spotted by the examiner it will fail the BSC check. Also single strand wire is not produced to deal with the vibration that a moving boat is subject to:rolleyes:
 
When I rewired my boat (the 12v side) about 28 years ago is used non-tinned stranded marine cable from ASAP Supplies, but I went a long way to prevent moisture corrosion of the copper. I used either crimp 'pin' fittings which had any seam solder-flooded on the cable end, or flooded the stripped end of the cable with solder, and then in both cases covered the end of the insulation and the start of the uninsulated copper with adhesive-lined heat-shrink tubing. This gave a fully watertight cable and a tinned end for making the termination connection, whatever the cable was for. Now I'm in the process of converting the boat from diesel-auxiliary power to electric motor and Lithium batteries. This inevitably has meant some re-modelling of the saloon and engine-room and some of that original cabling has become redundant so I have taken the opportunity to disect some of those cables to check how well it all worked. Well, after 28 years, and including a small 'flooding' event submerging some of the cables, the copper inside was still absolutely pristine. Now as part of having a large (48v x 600AH) lithium battery bank I'm planning on having full 'mains' functionality for cooking and heating running via a large DC inverter, so I'm looking at the 240v wiring. Not being able to find 3-core 2.5mm cable which is both tinned and rated for 240v has been a bit disconcerting, and I'm going to have to use Arctic 2.5mm three-core cable. I'm thinking of using my old approach of solder-flooding the stripped ends of the cores and sealing with adhesive-lined heat-shrink tubing. Can anyone think of any reason why not?
 
paul@jackman-graham.eu said:
..... Can anyone think of any reason why not?....
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IMHO: Seems like a sensible approach to me, using stranded H07 cable (as others have suggested - Elland do that) and using the methods you have stated should yield good results, of course tinned stranded if you can get it, the latter copes better with vibration long term.
 
John thanks for that - I'll have a look for that H07 cable. Of course now that I've removed that horrible old smelly noisy BMC 1.5 diesel and once the new Brushless DC motor goes in I'm seriously hoping for a noticeable absence of vibration!
 
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