12 volt cable...

[Timbo]

I need to start thinking about rewiring RT's 12 volt lighting and swapping out the harsh fluro type lighting in the galley adding new warmer lamps...possibly LED...my first question is what wire/cable and connectors etc do I need to buy...a link to the right item would be useful as you can tell I'm not an expert at this sort of thing!

[grendel]

I would suggest wiring as if you were going to use the original incandescent lamps, the wiring will then be plenty man enough for LED's but also be man enough if someone decides to retrofit incandescent bulbs.

Grendel

[Mowjo]

Grendel! ASAP are pretty cheap for cable, You'll only need 1mm2 cable for lights unless they are more than 16amps,  http://www.asap-supplies.com/marine/single-core-thin-wall-cables/single-core-primary-thin-wall-electrical-cable-1-mm, you'll have to decide if you want to run it in single or twin cable, if the lights have built in switches the twin is ok, if you have seperate switches like wall switches then singles are better, some say only use the tinned cable, I never use it and have never had a problem, as for connectors, you can use the chocolate box ones for connecting the cable to the light but I don't use them they have a habit of corroding and failing, your better off using crimp terminals like this kit, http://www.ebay.co.uk/itm/Toolzone-101Pc-Crimping-Plier-Tool-Kit-And-Terminal-Connector-Wire-Stripper-NEW-/140829406228?pt=UK_Computing_Other_Computing_Networking&hash=item20ca163414, you can use the straight connectors, or if you need to take the light off at anytime you can use bullet conectors, the only thing with those kits is you have to be a bit careful with the crimping pliers, too much pressure and you can cut right through the connector, you can get a pro version of the crimpers for around £25 but if your only going to use it once in a while the kit one will do the job Ok

 

Frank,,,

[BroadScot]

Most important of all...make sure all terminations are good n tight!  1mm is perfect for lighting BICC did the best twin cable without earth. Best cable make for not going brittle is Pirelli IMHO. Do not use the cheap white insulated type, it was always short of powder inside the insulation and a b.....r to strip back at times.. Just me, prefered using quality makes. 

 

Iain.

[Oddfellow]

Most people will realise this, but solid core cables should not be used on boats. Crimp connectors are preferable to anything else. Avoid screw type terminal blocks and never solder cables together or solder on connectors. 

[ranworthbreeze]

Most people will realise this, but solid core cables should not be used on boats. Crimp connectors are preferable to anything else. Avoid screw type terminal blocks and never solder cables together or solder on connectors.

I Agree with Andy regarding the use of suitable stranded cable on boats and crimped connection if the crimps are of the correct size and type for the job.

I would tend to use a screwed connection for preference over a crimped connection. All trades tend to use them these days because of the difference in speed.

One of the problems on boats is that all connection are effected by damp the crimped bullet connections are the worse of all and are frequently used on items that can be removed for servicing, such as bilge pumps, heaters etc.

Regards

Alan

[Mowjo]

Alan! I have to disagree about crimped connectors, they are all fine it's the people using the wrong tools that are the problem, the cheap crimp tools is worse than useless as they only crimp in one spot and just a little too much pressure and you can cut right through the connector, the only one I would ever use is the rachet type as they give a proper crimp and you can get them on E/bay now for under a tenner, I always leave a bit of extra cable so I can use straight connectors and just cut them off if I need to remove or replace stuff, but I've actually started using the Bullet connectors more and more, but now with all my crimps I use adhesive heat shrink tubing, I was working on the electric and found some of the crimps had water in now they are all watertight, as an extra I even use heatshrink on the ends of my ropes now, it stops them fraying and makes a nice neat end,,,

 

Frank,,,,

[Oddfellow]

The big problem with crimp connectors is people who handle them wrong..... Pull the plugs apart, not the cables.

 

Screw terminal blocks should not be used at all - I know they are common, but they are hugely prone to corrosion and forbidden under BMET regulations. 

 

Frank, you can also buy a product called Liquid Whipping which is a latex type product that cures in air. Dip the end of your rope in, allow to dry and hey presto, a "whipped" end. 

[Mowjo]

Hi Andy! I have seen that stuff but never tried it, I always used to use the normal heatshrink but now I've switched to the adhesive one so I get double protection, like you I won't have terminal blocks anywhere on the boat for the reasons you said, it's the first thing I check for when I get a boat, I even change all the fuse boxes over to the blade type or the ring terminal ones, the only problems I've ever had were caused by the screw clamp type or the ceramic fuses corroding, no I only use the blade type, I'll use a terminal block as an emergency repair but change it over as soon as I can, my trouble is I keep finding them hidden away under bunks and often tucked into the roof for the lights, another habit I have is if I find more than one join in a cable I rip it out and re-cable it, I'm probably a bit OTT with my electrics and check them once a year, but better safe than sorry I think, I've seen too many boat, car and house fires due to dodgy wiring,,,

 

Frank,,,,

[Oddfellow]

Important points, Frank. 

 

The absolute rule with any connection is accessibility. 

 

One of the attractions of a terminal block screw connection is the ability to attach it to something with a screw through it. This is something that isn't directly achievable with a Bullet or Spade connection. Yet, the connection should really be supported.

 

We use various methods including spiral wrap and then a couple of P clips to support the loom.

 

We are doing some electrical installs and fault finding on a private boat now and locating some real horrors. This was discovered in a 240v mains circuit yesterday that we are extending to provide anti-frost protection and battery charging. Care should be used when stripping cable sheathing..... (sorry image is the wrong way round)

 

[MauriceMynah]

Doesn't anyone make a screw terminal block for marine use where all the metal parts are brass?

[Guest]

.....We are doing some electrical installs and fault finding on a private boat now and locating some real horrors. This was discovered in a 240v mains circuit yesterday that we are extending to provide anti-frost protection and battery charging. Care should be used when stripping cable sheathing..... 

 

"Care should be taken when stripping cable sheathing"....

 

Andy's photo showing the core insulation nipped near the cable butt is a frighteningly common sight.

 

Even the most basic wiring skills may seem very simple, but it's so easy to get it badly wrong if you've never been shown the correct way.

 

So many people expose the inner cores of a multi core cable by simply nibbling around  the sheath with a pair of wire cutters or scoring round with a knife. The correct techniques is to slit the sheath back with a light scoring lengthways and then pulling it back while holding the bunch of inner cores. That way there's no chance of damaging the individual wire core insulation at the butt, (the point where the individual wires emerge from the outer sheath).

 

I've rewired all 4 houses that I've owned, and 3 of the boats, because of serious faults and dangerous workmanship like this.

 

My current (25 year old) boat was equipped by the manufacturer with bespoke  high spec 12 and 240v supply panels. Very neat and impressive, but the wiring behind was appalling. All of the 240 volt 3 core cables had been stripped the wrong way, with deep cuts through the inner insulation, just like in Andy's photo. 

[grendel]

you can get sticky pads designed especially to fit cable ties through, these help fix the wiring looms once they are cable tied together. you can also get ones that can be screwed to the surface for fixing (google cable tie bases)

Grendel

[Mowjo]

Andy's picture of a classic example of why I will never advise anyone on installing 240v, what surprises me most is when I had my BSS done a few months ago I noticed the examiner never even looked at the 240v when I asked why he told me it's not part of the examination, very suprised at that as it's the one thing guaranteed to kill you if it's wrong, if you check out auto elecrtic suppliers you'll find a whole range of different cable fixings, I clip all my cables with the correct size P clips about every nine inches and my mains cable is clipped every six inches, as Strow points out even the so called Pro's can do a bad job so when anyone ask's I always advise them to have them checked, most people don't even realise that in the right circumstances even 12v can kill you, I can't swear to it but I think it's the Ampage that can kill you not the voltage, apart from that dodgy wiring can and does cause a lot of fires on boats or in cars, so if in doub't leave it alone and get someone that knows what they are doing to do it for you,

[Mowjo]

Maurice! the reason I don't like the block is the actual screw, it tends to cut into the core wires, so you never reall gat a full connection,,

 

They do these nickle plated ones,

http://www.force4.co.uk/holt-marine-terminal-block-12-way-10amp.html#.VEaG5Bbtd-w

 

And I've just discovered these, I havn't tried them yet but I have some on order,,

http://stores.ebay.co.uk/A1-DISTRIBUTORS/CONNECTORS-WAGO-/_i.html?_fsub=2956756013

[BroadScot]

 

so if in doub't leave it alone and get someone that knows what they are doing to do it for you,

 

Correct!!!

 

Iain.

[Mowjo]

Iain! I think I'd better not mention that one my first real boat thirty years ago, I completely re-wired the whole boat right back to the engine, new fuse boxes, busbars you name it I re-fitted it, but as I had been used to the old black and red cables, and I was using the relativly new blue and brown wires, I somehow got it into my head that the blue was live, so I re-wired the whole boat using blue as live and brown as neutral, it was about a year later when I went to add a new bilge pump that I realised what I had done, but too late I wasn't ripping it all out again, I kept the boat for another five years then sold it via a broker, I pity the poor S*d that bought it I bet they did a bit of head scratching and cursing the last owner,

 

Frank,,,,

[Guest]

......most people don't even realise that in the right circumstances even 12v can kill you, I can't swear to it but I think it's the Amperage that can kill you not the voltage.....

 

It's quite safe to touch low voltage DC (eg 12 or 24) with your hands, because the human body's internal resistance is too high for it to pass through. The danger with it is when it is shorted out with low resistance objects at high amperages, because of the extreme heat generated.

 

When I was an apprentice in the GPO we were forbidden to wear metal rings, metal wristwatch straps, or metal glasses frames when working on the high amperage DC circuits in the telephone exchange.

 

Even a typical 12v boat battery can instantly melt any of those items, with terrible burns or worse.

 

The standing voltage on telephone circuits was 50v DC, but in the equipment racks the busbars were carrying hundreds of amps. 

 

Most exchanges had a black museum of wire cutters and screwdrivers that had melted into shapeless blobs, (in a fraction of a second).

[Mowjo]

Thanks Strow! I thought I was sort of right even though I've only ever heard of one case where it did actually kill someone, but he had a pacemaker fitted so I presume something affected that, basically what I was trying to say is never underestimate your 12v system, it's not as harmless as we think, when I'm out looking for a new boat, I'm on No7 now, the first things I check are the engine, because if it's nice and clean the chances are the owner has taken a bit of care of it, the next is the electrics and in nine out of ten boats I've looked at they are sub standard or even dangerous, and believe me I've looked at hundreds over the years, I've seen everything from domestic solid core twin and earth to bell wire being used, how there arn't more boat fires I'll never know, when I bought my Freeman Dragonfly I found six joins in a three foot lenght of cable and one of the bits in the middle was a bit of orange extension cable,,

 

Frank,,,

[Jonathan]

It's quite safe to touch low voltage DC (eg 12 or 24) with your hands, because the human body's internal resistance is too high for it to pass through. The danger with it is when it is shorted out with low resistance objects at high amperages, because of the extreme heat generated.

Whilst I agree with this, I would add that this is true for dry skin.  If you have got wet (which never happens on a boat!) then it is more dangerous.  I had a quick google and found the table "Currents Resulting From Electric Shocks" at http://www.mpoweruk.com/shock.htm;this only lists currents at various voltages, 50V being the lowest, so divide by (approximately) 2 for 24V and 4 for 12V systems.  There might be better data elsewhere.

[Baitrunner]

You would have to be the most unlucky person in the world with the lowest resistance to electricity and the weakest heart to get a fatal shock from a 12v system. It simply hasn't got the volts to push a fatal current through the human body. As mentioned it's the current that kills.

 

I bet some of you tried the 9v battery on the tongue when you were younger to see if really hurt - probably got a bit of a tingle.

 

Now that doesn't say you shouldn't take care either - if your stupid enough to grab both terminals of a battery (or loose live and negative wires) with wet hands then to be honest you need a shock! 

 

Don't forget that a lot of incidents with 240v is because your earthed - no earth on 12v DC systems so unless you have a metal boat and don't wear shoes a short to the hull/deck isn't going to matter (plastic/wood tend not to conduct very well). So you would need to be very unlucky even with badly fitted electrics.

 

If in doubt (in fact ALWAYS) turn the isolators off before doing work on ANY electrical system.

 

If your working on a system that uses high voltage DC then be very careful - DC makes you stick whereas at least AC (normal mains) tends to throw you off. You might find high voltage DC in an old TV or radar system, but on our boats these will be pretty low current devices and why would you fiddle in one of these units?

 

I had to work on a 600v DC high current power supply for a high power radio transmitter - now that you don't want to touch!!!

 

The 50v DC used on phone systems was always a source of amusement for the apprentice games if I recall and didn't hear of any fatalities. But wouldn't stick my tongue on it though!!!  

[Guest]

Back in the  cathode ray tube TV days, the line output transformer generated 27,000 volts to the tube on a colour TV.

 

I knew a brave (but foolhardy) TV repair engineer that used to test the HV output by touching a wooden handled screwdriver against the cap and then pulling it back to measure the gap that the arc could jump. He reckoned about an inch was the correct "measurement" 

[grendel]

I once made a painful mistake with an old 90v radio battery - fortunately it only had about 20v left when I stuck it across my tongue, boy what a headache that left.

I am fairly lucky to be blessed with a high resistance thankfully after several incidences with mains electrickery (remember to turn off and unplug from sockets before getting a knife out and cutting the cable off an appliance).

Grendel

[BroadScot]

This thread should be changed to 12volt cable and survived the shock!

 

Iain.

[MauriceMynah]

I remember as a kid I put my tongue across the track of my scalextric and pushed the go button! What a prat, it hurt quite a bit. However, just to prove I was a top level, 22 carot prat, I did the same thing again a year or so later!!!