running downlighter spurs without cutting main cable

[Moisha]

Hi all. We are steady on and finally (months after the intended time) are actually beginning our electrics. A quiestion came.... We will be running light circuits with a separate spur for each light. I know that in household electrics when more than 2 wires are connected they use these bulky junction boxes/ But I was wondering if there was a way of doing it by somehow attaching the spur cables to the main one without cutting it. I imagined some sort of crimp connection that 'clips onto' the main cable at a part that would be stripped of insulation. Does anyone have any suggestions? Is there a standard way of doing it?

 

Much appreciated, as always.

yours, moisha, Esq.

[Moley]

We will be running light circuits with a separate spur for each light. ... I was wondering if there was a way of doing it by somehow attaching the spur cables to the main one without cutting it.

 

Not a standard way of doing it, but when I ran my pairs of feed and return wires I had a good idea where my lighting was going to spur off, and ran pairs of appropriate guage chocblock connectors along the wires into approximate position. When I ws ready to take off a spur I trimmed half an inch of insulation of both cables, slipped the chocblock over the exposed length, slipped in my spur wires, and held both wires with both screws.

 

This, to my mind, gives a more secure connection, and the main run of cable remains unbroken.

[dor]

In my view, the best way to take off a spur for an individual light is to strip back about a cm of insulation, then solder the spur wire to the main wire, with most of the cm soldered. Then use self-amalgamating tape over the connection to finish.

[Moisha]

Duh--soldering should have been an obvious option!

[chris w]

Note that Dor (quite correctly) advised you to use "self-amalgamating" tape. Do not use normal insulating tape as within a few months it will have deteriorated and become a sticky mess. Self-amalgamating tape, on the other hand, will form a permanent, waterproof, stable insulation over the joint. Maplin sell it, as well as places like B&Q. IIRC B&Q call it something like "self-fusing" tape. It's quite a bit more cost than insulating tape (about £5 a roll as compared to about 30p for insulating tape but it's the dog's danglies.

 

If you've never used it before, simply cut off a length (shorter than you think because it stretches), stretch the tape to break off the backing film and, while keeping it stretched, wrap it around the joint and finish off by wrapping the end back on the main taped joint. The tape is not sticky and will only "stick" to itself. Within a few days it wil have "amalgamated" into an homogeneous. totally waterproof covering (which can be cut off with a Stanley knife if ever necessary).

 

Chris

Edited April 2, 2007 by chris w

[Moisha]

Hey--do these kinds of connector strips do the trick???

http://www.toolstation.com/shop/Electrical...ent/d190/sd2460 the many-way 'connector strop' on the page. Are these cut into small bits and used as mentioned or are you talking of something else?

 

Thanks a million again.

moisha

 

 

Not a standard way of doing it, but when I ran my pairs of feed and return wires I had a good idea where my lighting was going to spur off, and ran pairs of appropriate guage chocblock connectors along the wires into approximate position. When I ws ready to take off a spur I trimmed half an inch of insulation of both cables, slipped the chocblock over the exposed length, slipped in my spur wires, and held both wires with both screws.

 

This, to my mind, gives a more secure connection, and the main run of cable remains unbroken.

[Moisha]

It seems there are these things called 'tap connectors' that attach a 'tap' to the main wire. Some are self-stripping and look quite handy. Although few take wires thick enough...

 

moisha

[Moley]

Yes, that's the sort of connector strip I was talking about. Cut them as required.

 

Soldering would be the best option, if you have mains onboard and if you're not working above your head. I found those connectors easiest in my circumstances.

 

It seems there are these things called 'tap connectors' that attach a 'tap' to the main wire. Some are self-stripping and look quite handy. Although few take wires thick enough...

 

I think you're talking about Scotchloks. Don't.

[Big Steve]

Screwfix do nifty little boxes specially designed to hold a 3 way connector strip. If you go the soldering route, slide some heat shrink sleeving over the conductors and cables first, when you've done soldering slide the sleeves into position and zap the whole lot with a heat gun. Finish off with amalgamating tape for a real tough job.

 

Personally, I think the connector strip is easiest and just as good as soldering, but it does take up a bit more room and isn't quite as elegant.

[ChrisPy]

I think you're talking about Scotchloks. Don't.

This advice has been given several times. What is the hazard? If it is just that there may be a poor or unreliable connection then that is manageable and can be fixed, especially if all the cable junctions are accessible. If there is a serious hazard like a fire risk, then that is a different matter.

 

Please can someone clarify what is the hazard?

[Gary Peacock]

Scotch locks aren't so much dangerous but just considered a bit "iffy "in principle.

 

The main problem being misuse of the wrong cable or lack of adequate support at the connection causing the blade in the connector to cut the strands work loose and cause a poor connection, in damp areas the dissimilar metals used at the connection can cause corrosion eventually causing a failure too.

 

In reality used correctly on a boat they are probably far better suited to this than their use in the automotive industry where they first appeared and moisture and vibration causes them to fail often.

 

We use crimps (Not the RED/Yellow/Blue variety) the correct crimps crimped with the correct crimper give a strong electrically and mechanical connection that is fast and easy it is still good practise support the connection but that can be done by simply cable ties around the cables prior to the crimps to remove any potential strain.

[Boaty Jo]

We use crimps (Not the RED/Yellow/Blue variety) the correct crimps crimped with the correct crimper

 

Which crimps Gary if not the Red/yellow/blue?

[Gary Peacock]

We use crimps (Not the RED/Yellow/Blue variety) the correct crimps crimped with the correct crimper

 

Which crimps Gary if not the Red/yellow/blue?

 

 

 

They come in various sizes from RS or Farnell's link to one size on RS HERE

 

You can get away with crimping them with a ratchet crimper for R/Y/B crimps but the specialist one for them is better.

 

If you go up a level from that link there are some interesting variations on scotch locks too! If I were building my own boat I would be very tempted to use them because if they failed I could replace them but when you're building other peoples its got to come down to better safe than sorry.

Edited April 3, 2007 by Gary Peacock

[chris w]

I used Scotchloks extensively on a kit-sports car a few years ago with no problems from vibration etc. The real secret is to use the correct size for the cable in question. Most failures that friends of mine had with Scotchloks came about through using what they thought was a "standard" (blue) one with very thin wires. Not compatible.

 

I also love crimps which are inherently stronger. The problem with these though is some people don't use a ratchet crimper but the cheap £5 jobby that comes in a lot of crimp kits. The proper ratchet crimper produces both an electrical bond to the wire AND a mechanical bond to the sleeving and applies a lot more pressure than is achievable with the simple hand crimper.

 

Soldering also of course produces a great electrical bond and a very good mechanical bond. One issue though, from the mechanical point of view, can be that solder joints under vibration can fail at the point where the solder ends and the wire commences again through mechanical flexing. This is why aircraft use crimp joints not solder joints,

 

Chris

[ChrisPy]

All my lighting connections are spurred off using scotchloks. In fact the size of my cables (4sq.mm) was fixed because that's the biggest scotchlok I could get (yellow), so I had to install more black and red cables than if I had used 6sq.mm which seems to be the norm. Like ordinary crimps, you must use the correct size to match your wire and you must use the correct pliers to close the lock device. Scotchloks use the same type of blade cutter/grip that has been used on telephone cable joints for decades, and they don't often fail if left well alone.

 

I can't get my head round the frequent references to damp conditions in boats, and how it causes corrosion. Understandable in a salty boat that may get salt spray under its skirts occasionally, and that may apply to Elessina, but never to Slithy Tove! The only connections I have below waist height are at the various pumps, and there's no need for tee-joints there.

 

Solder is for neat copper pipe fabrications, not for lekky cables. That's my motto and I'm sticking to it.

[Guest]

All my lighting connections are spurred off using scotchloks. In fact the size of my cables (4sq.mm) was fixed because that's the biggest scotchlok I could get (yellow), so I had to install more black and red cables than if I had used 6sq.mm which seems to be the norm. Like ordinary crimps, you must use the correct size to match your wire and you must use the correct pliers to close the lock device. Scotchloks use the same type of blade cutter/grip that has been used on telephone cable joints for decades, and they don't often fail if left well alone.

 

I can't get my head round the frequent references to damp conditions in boats, and how it causes corrosion. Understandable in a salty boat that may get salt spray under its skirts occasionally, and that may apply to Elessina, but never to Slithy Tove! The only connections I have below waist height are at the various pumps, and there's no need for tee-joints there.

 

Solder is for neat copper pipe fabrications, not for lekky cables. That's my motto and I'm sticking to it.

Some people argue (which means some don't) that if you solder a flexible cable, you are making that portion of it into a solid cable.

I always feel crimp connectors are the most reliable, but a pain if you wish to disconnect anything. I have always stuck with quality screw connectors, but with boot lace ferrules on cable ends.

[John Orentas]

You won't be surprised to hear that I disagree with the lot of you. We should not be joining cables behind linings at all, they should all be wired right back to the distribution / fuse panel. Where connections are unavoidable they should be done using the 1/4" receptacle crimp connectors. Those tatty Scotch-lock things are OK for wiring your tow-bar that may be in place for 5 years or so, your boat should be built to last at least 30 years.

 

Soldered connections are OK but you need some extra reinforcement and insulation, heat shrink sleeving or self amalgamating tape is good, I tend to use both, tape first, then sleeve on top.

[Guest]

You won't be surprised to hear that I disagree with the lot of you. We should not be joining cables behind linings at all, they should all be wired right back to the distribution / fuse panel. Where connections are unavoidable they should be done using the 1/4" receptacle crimp connectors. Those tatty Scotch-lock things are OK for wiring your tow-bar that may be in place for 5 years or so, your boat should be built to last at least 30 years.

 

Soldered connections are OK but you need some extra reinforcement and insulation, heat shrink sleeving or self amalgamating tape is good, I tend to use both, tape first, then sleeve on top.

Bloody 'ell John, I'd need about a 40way board mate!!!!!!!

I exaggerate of course, but the looping of several lights on one circuit was inevitable I'm afraid in my case. You either have a seriously large dis board, or not many circuits.

[ChrisPy]

You won't be surprised to hear that I disagree with the lot of you. We should not be joining cables behind linings at all, they should all be wired right back to the distribution / fuse panel. Those tatty Scotch-lock things are OK for wiring your tow-bar that may be in place for 5 years or so, your boat should be built to last at least 30 years.

 

Soldered connections are OK but you need some extra reinforcement and insulation, heat shrink sleeving or self amalgamating tape is good, I tend to use both, tape first, then sleeve on top.

nope, not surprised at all ....

 

comparing with tow bar connections - they suffer a pretty tough life. I would call it an accelerated ageing test !

 

I have 21 lights at the last count. I am certainly not going to run 42 wires back to the panel! Oh, and run another one every time I decide to fit a reading lamp or summat ? I don't think so. Let's get real, John

 

If I have to attend to a couple of scotchloks after 5 years or so when the connected light starts flickering I won't be too disappointed.

 

's OK, still friends

[Moisha]

Hi All,

 

This is Jon (the other member of Moisha who has not chimed-in so often).

 

My idea was to strip about half an inch of the trunk cable (which in one case, for the furthest lighting circuit, has a 10mm squared cross section), strip about an inch off the branch cable (2.5mm squared), wrap the stripped branch cable around the stripped trunk, twist off and then solder them in; then use amalgamating tape. Soldering makes sense to me, but I've never soldered to anything as heavy as 10mm copper cable.

 

I imagine that the 10mm cable acts as a heat-sink, but an engineer friend is bringing a gas soldering iron to help us.

 

My brother and his friend also feel uneasy about soldering such heavy cables because they suspect that the soldered joint could be a fire risk. They thought that one must use big terminal blocks for this reason. Does anyone have a view on this? I assumed that if the copper of the trunk- and branch-wires are firmly in contact within the joint, there would be no risk. I can imagine if solder alone bears the current, then it will melt and melt the insulation too.

 

Using terminal blocks would be harder for us because, the way we've planned it, there's limited room behind the panel to house the lighting cables and terminals.

 

Any thoughts?

[Big Steve]

The way you've described that connection, your not cutting the main cable, just stripping back the insulation and wrapping the junction wire around it , then soldering it. In this case the solder is only carrying the current for the spur, and in any case, the main conductor shouldn't get above 70 degC, which will not affect the solder. Also, the 10mm^2 cable isn't carrying a vast amount of current, it's just that size to control the volts drop.

 

You will need a 100watt decent soldering iron for 10mm. I like Wellers. The instant heat ones with a trigger on are pretty good for heavy work. One of these http://www.toolshopdirect.co.uk/handtool/product/WEL9200UD should do it.

[DHutch]

All our lights are wired with hard power, and are switched only with the interal switch.

- So this end, each lighting feed simple daisy chains from each light on the feed to the next, behind the line out.

- The are four seperate feeds from the dis box, each feeding about 4/5lights in one or two room thoughout the boat.

 

This is very much what is done in a house, and it works well.

- If i was doing it another boat, i would do basicaly the same again. Although for ergonomic use reasons, would proberbly also and some gunnel leval switches.

 

The junctions are mainly screwdown chocolate-block-type conectors within the light fitting. With the stranded cable being crimed into suitable end fitting before being placed into the conector.

 

 

Daniel

[Big Steve]

Has anyone tried running a lighting ring main? You could get away with smaller cable doing it that way, but I've never seen it done. Can't see why there would be a problem.

[NB Willawaw]

Personally, I wouldn't do it this way. You are relying on the wires making contact by wrapping and the solder to bind weaknesses in the wrap.

It might work, but its not a particularly tidy way to do it and nobody knows what the long term effect would be on this method (solder can give dry joints with age and how are you going to ensure that the sodler provides a good bond with the copper ??)

 

I would do it with terminal blocks that provide a more positive form of connection and make fault finding easier should it be necessary later on.

They don't have to be huge..

 

Hi All,

 

This is Jon (the other member of Moisha who has not chimed-in so often).

 

My idea was to strip about half an inch of the trunk cable (which in one case, for the furthest lighting circuit, has a 10mm squared cross section), strip about an inch off the branch cable (2.5mm squared), wrap the stripped branch cable around the stripped trunk, twist off and then solder them in; then use amalgamating tape. Soldering makes sense to me, but I've never soldered to anything as heavy as 10mm copper cable.

 

I imagine that the 10mm cable acts as a heat-sink, but an engineer friend is bringing a gas soldering iron to help us.

 

My brother and his friend also feel uneasy about soldering such heavy cables because they suspect that the soldered joint could be a fire risk. They thought that one must use big terminal blocks for this reason. Does anyone have a view on this? I assumed that if the copper of the trunk- and branch-wires are firmly in contact within the joint, there would be no risk. I can imagine if solder alone bears the current, then it will melt and melt the insulation too.

 

Using terminal blocks would be harder for us because, the way we've planned it, there's limited room behind the panel to house the lighting cables and terminals.

 

Any thoughts?

[DHutch]

Has anyone tried running a lighting ring main? You could get away with smaller cable doing it that way, but I've never seen it done. Can't see why there would be a problem.

You certainly could, and our 240v sockets are wired in a ring, running right round under the gunnel.

- How ever, you do get to a point where its not overly worth it. Narrowboat are just so long and thin!

- What you could do though, it wire a room in a ring, and then wire that ring backto the board from there.

 

 

 

Daniel