Crimping t/y splice into 16mm2 cable

[towpathrider]

I said earlier how I would do it if I had to do it with 16mm. The 4x 12v oulets that I inherited on this boat are wired in 6mm, daisy chained using 30amp terminal block one run down each side of the boat, voltage drop has not been a problem.

Personally I don't use 12v for high current items prefering to use 230v for that. I run my USB chargers, dongles etc from 12v but that's about it. My last boat had no 12v sockets at all.

As for choice of cable I use tri-rated which is overspeced for the job but is of a consistent standard unlike many "auto" cables.

By terminal blocks do you mean chocolate block connectors? When getting the boat a couple of years ago the surveyor seemed particularly anti those, and I dont think they provide an ideal mechanical or electrical connection. Plus not sure I could get large enough ones for 16mm.

 

I'd also like to avoid cutting the 16mm where possible.

 

 

At the risk of sounding facetious Should I be worried about vibration with copper gas piping, or indeed in my alternator?

 

Hopefully I can find multi strand at a good price, though (call me stubborn) I would be very surprised if the cable broke within the lifetime of the boat.

 

Has anyone experienced this happening with heavy gauge cable, which has been frequently secured (say every 10cm or so) throughout its length?

 

As I mentioned earlier, my boat was wired fairly extensively with solid strand wire, some of it poorly secured. None of it had broken, or even appeared brittle.

 

Some of the multi strand wire had, however turned black inside the insulation and become very brittle - almost dusty. Presumably due to moisture/oxygen getting under the insulation, which is what the better marine tinned cable should avoid.

Edited April 12, 2016 by towpathrider

[GUMPY]

I have seen stranded 50mm cable soldered into crimps break through vibration so it does happen.

Terminal block is fine provided you use bootlace ferrules on stranded cable. If you don't its crap way of connecting cables.

[towpathrider]

Ok thanks for all the advice, I will try and source some stranded wire. It still seems theres no easy or straightforward way to wire multiple connections to the 16mm though.

[Afloat]

Something I use alot for certain jobs,

 

http://www.klauke.com/katalog/en/tv15-t-connectors-cu-standard-type/

 

but it does mean cutting the cable.

Edited April 12, 2016 by Afloat

[WotEver]

Some of the multi strand wire had, however turned black inside the insulation and become very brittle - almost dusty. Presumably due to moisture/oxygen getting under the insulation, which is what the better marine tinned cable should avoid.

Yes, your description of copper wire corrosion, it's cause, and the best way to avoid it are all correct. In my experience though, most of the times I've seen this it's been exacerbated (or perhaps started?) by a poor connection at the termination. The resultant heat in combination with moisture has (I believe) caused the corrosion to be worse than it otherwise might have been.

 

Tony

[FadeToScarlet]

Is it really that bad to cut the cable?

 

I mean, if every joint is in a junction box so is easily accessible, and it has proper hydraulically crimped on ring terminals, they're unlikely to come off, especially if there's some form of strain relief on the cable so it's never pulled.

 

Worst case scenario, one of them comes loose and the sockets "upstream" stop working; easy enough to see which joint has failed, open the box,and crimp on a new connector and reattach. Five-ten minute job? As easy, or easier, than fiddling with some kind of proprietary connector or a soldered joint that will probably crack and need resoldering.

[MtB]

Is it really that bad to cut the cable?

 

 

I'd say it is preferable not to whenever possible, as each cut means unnecessary junctions, and each junction introduces a potential for a bit of resistance to develop either from the get-go or with the passage of time.

[nicknorman]

Ok so first of all on the regulations, one can argue that this particular bit of this regulation isn't necessary in this particular circumstance, but that is what is generally called "re-inventing the wheel". There is a danger that a factor is overlooked and so it is better and simpler and usually not difficult just to go along with the regulation. The BSS is not that prescriptive on wiring. However the European standard that is the RCD (recreational craft directive) is a sound place to start. The RCD refers to ISO 10133. There seems little excuse not to comply with this ISO for a major rewire. So multi strand cable of the correct colours, ferrules for any screw connections etc.

 

If I were doing what you intend to do I would do it thus: prepare a section of the wire where you want to take the tap by stripping back 2x the crimp length and then double that bared section over to insert into a ring crimp. Of course this requires a crimp twice the size of the cable. Whether you end up cutting the cable or just bending it back isn't going to make any difference to circuit integrity though I guess the bending solution might be difficult to get into the crimp. Use a ring crimp and connect to an insulated bus bar. Take your tappings from that, via a fuse board if the overall fuse size is greater than the individual circuit wire - and bear in mind that you don't really want the whole system being taken out by a short circuit in one circuit.

 

We have the same concept on our boat but have an electronic system that takes the "ring main" 12v thick wires and switches multiple outputs to services via electronic fusing. It works well.

 

If you are proposing to use cable unsuitable in construction and colour just because you got a cheap job lot, you are a no-hoper. Sorry that is harsh..... But true.

Edited April 12, 2016 by nicknorman

[DHutch]

I could start an argument now by making the statement "voltage drop is not as important as it's made out to be"

 

I does also seriously depend on what the OP is planning to run of it, and how often.

 

We have a number 24vdc 'extra low voltage' sockets around the boat powered from the battery, and quite honestly we basically don't use them ever. In total there is about ten of them, and we use two, intermittently. One for a 20watt incandescent table lamp infrequently, and one for a pair of 200mm dia fans used to assist draft on the boiler when in a cutting with down draft, maybe twice a year. The waterpump, fridge, showerpump and lights then have their own feed.

 

A digression perhaps, but 16mm^2 seems big even for a 12v layout.

 

 

Daniel

[nicknorman]

 

A digression perhaps, but 16mm^2 seems big even for a 12v layout.

 

 

Daniel

Not really, if it's to supply all services.. We have a 16mm "ring main". Bear in mind that some services like the water pump are often at the far end of the boat and you don't want the lights dimming/flickering too much when the pump starts with its big transient current demand. Fridges require a low resistance connection too.

[ditchcrawler]

There are several points IMO. We don't know what size fuse the OP intends to protect this circuit with and we don't know what he intends to feed with it.

He talks about several sockets and some fixed items, he mentions may by 10 amps from the socket for Laptop a TV and other items, but we don't know the total maximum loading of the complete circuit, if only briefly.

[Tony Brooks]

 

 

 

Snip

 

 

I will be running several sockets, and a couple of 12v applicances directly from this 16mm2 circuit, each socket is fused, and each appliance will be fused as well. I plan to use 6mm or 4mm cable for the spurs.

 

Max current draw from any one socket will be 10a (occasional use of powerful laptop)

 

The appliances will be a small tv/monitor, 12v stereo, and maybe a couple of 5v usb devices via a buck converter.

 

 

I'm not set on doing it "my way", otherwise I wouldn't have bothered with the post,

If you were to wire 16mm2 12v to "best practice" standards how would you do it?

 

 

Figures from VWP catalogue.

 

16 sq mm CCSA cable is rated at over 100 amps

 

6sq mm CCSA cable is rated at 50 amps

 

4 sq mm CCSA cable is rated at 39amps

 

If you do not fuse individual spurs AND and cables fitted to appliances by the manufacturer are l 4 sq mm CCSA or larger then a single 39 Amp fuse on the main ring should suffice. That is if the combined loads on the main cables is always less than 39 Amps. If the combined load is more then the main cables should be fused at up to 110 Amps while each spur should be fused for the maximum current the spur cable is rated for. Not at the sockets or appliances but as close to the main cable as possible.

 

Personally, although I would never advocate it, I think the proposed 16 sq mm CCSA will be long lasting and do the job, especially as the OP says he proposes to fix it at 100mm/4" centres.

 

However at some future date someone could well have a fuse blow, look at the size of the cable and fit a larger fuse. This would then create a fire risk if one of the smaller cables shorted out. Not best practice in my view.

Edited April 13, 2016 by Tony Brooks

[John V]

^^^ Fully agree and it's clearly explained

[raymondh]

Depending on the proposed cable colour (green/yellow?) in a future job it may be thought of as an earth wire and used in a mains voltage circuit ?

 

Ray

[DHutch]

Not really, if it's to supply all services.. We have a 16mm "ring main". Bear in mind that some services like the water pump are often at the far end of the boat and you don't want the lights dimming/flickering too much when the pump starts with its big transient current demand. Fridges require a low resistance connection too.

 

Well yes, if you really are running everything of it then fair enough.

- As said, we have the fridge and the two pumps off their own dedicated feed, ditto the lights are on three circuits front/middle/aft which combined with the boat being 24vdc means a 2.5mm^2 ring main is more than enough.

 

 

Daniel

[DHutch]

Depending on the proposed cable colour (green/yellow?) in a future job it may be thought of as an earth wire and used in a mains voltage circuit ?

 

I would suggest that if it is indeed yellow/green it would be wise to sleave it a more suitable colour, or mark it clear as to what is is both and each junction and at intervals between if longer than say 1000mm.

 

 

Daniel

[smileypete]

Don't know if OP is still looking for a solution, something like this might help:

http://www.theelectricalwarehouse.com/product.php/389107585



I *think* it can take 2x 10mm² under each screw, so 16mm² and 6mm² should fit well enough. Worth using a bootlace ferrule on the 6mm² if fine stranded.

Though not ideal, I'd expect 7 strand is perfectly functional on a private inland narrowboat for non engine wiring, if well supported, and RCD compliance is not required. Plenty of such boats in the past have been wired for mains in T&E and I've never heard of any problems with breakage.

cheers, Pete.
~smpt~

Edited April 14, 2016 by smileypete

[towpathrider]

Thanks for the replies, I've actually found some multi stranded cable that is reasonably priced, so will probably go with that, had I gone with the earth wire then I would mark it using electrical tape at regular intervals so that it was clear which was positive and negative. I also plan to have a wiring diagram clearly placed in the engine room for my own, and any future owners use.

 

The choice of 16mm wire was purely down to voltage drop, this circuit will ONLY be for sockets and a few devices, (fridge, lights pumps are wired on separate circuits) but as I mentioned I have a powerful laptop that I would like to be able to use occasionally, (yes I know!) and If it was used at the far end, (most likely, as this is the seating area) then a 10 amp draw at 12v over 15m would mean a voltage drop of nearly 5% - to about 11.9V, and that's if nothing else is attached to the circuit.

 

It might seem stupid to size the circuit according to one device that won't be used all the time, but since it's only something I am going to do once I'd like to have that option.

 

I don't expect to draw 30a from the whole circuit at any one time, so will fuse it at 30a on the 12v distribution fuseboard, and yes, I will fuse each additional spur as well. As I will be using 6mm2 and 4mm2 for spurs their current carrying capacity will not be exceeded without blowing either the main 30a fuse or the spur fuse.

 

I beleive the maximum rated ATO fuse is 40a, so if someone did replace, that's the maximum.

 

 

as to the connections, I have found these open copper crimps http://www.amazon.co.uk/10Pcs-Open-Copper-Terminals-Wire/dp/B00R1IYCNK/ref=sr_1_2?ie=UTF8&qid=1460738116&sr=8-2&keywords=open+copper+crimp+10 - which could be crimped to a stripped but unbroken wire, I then plan to use to heatshrink tape and/or self amalgamating rubber for insulation. If properly sized to the cable and well crimped, I would have thought this should made a good mechanical and electrical connection?

Edited April 15, 2016 by towpathrider

[RLWP]

It might seem stupid to size the circuit according to one device that won't be used all the time, but since it's only something I am going to do once I'd like to have that option.

 

 

Not stupid at all, quite the opposite

 

Richard

[smileypete]

Would have thought that 10mm² will drop 0.5V over 15m at 10A

 

Must be a powerful lappie, what output volts/amps is the mains adapter? Most are 65w these days.

 

Could use two runs of 6mm2 trirate, then tap off using yellow piggybacks - bearing in mind the yellow blades are only good for ~20A. Not that keen on piggbacks myself, would prefer ring terminals to bolts.

 

BTW nothing intrinsically wrong with pre insulated crimps IF a decent ratchet crimper (eg cablecraft or similar) and quality terminals (eg meeting BS4579 and BS4G178) are used.

Edited April 15, 2016 by smileypete

[RLWP]

Of course, as soon as the cabling is done the laptop will pack up. And the new one will use less power

 

Richard