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Old 02 March 2008, 18:38   #11
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Originally Posted by jwalker View Post
The scotch connectors are normally used for connecting to a cable already in place so you can't fit shrink sleeving onto the cable.
You hit the nail on the head JW - that's exactly the problem. Thanks for the detailed advice on a decent solution though
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Old 03 March 2008, 12:56   #12
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Originally Posted by jwalker View Post
The scotch connectors are normally used for connecting to a cable already in place so you can't fit shrink sleeving onto the cable.

If you are considering using a Scotch connector to add another wire to the middle of an existing wire you have to either cut said wire or remove some insulation, fold the wire and push it into the block. Therefore you could instead cut the wire, slip on some heatshrink, make the joint and then slide the heatshrink into place. Or strip off some insulation, fold the wire in half, slip over some heatshrink, solder the new wire onto the stripped area, push the heatshrink over the join and shrink (or slide the heatshring along the new wire before soldering). This assumes sufficient play in the cable but if there is none a Scotch connector won't fit either.
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Old 03 March 2008, 13:39   #13
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Originally Posted by TangoTango View Post
This assumes sufficient play in the cable but if there is none a Scotch connector won't fit either.
It's rare there is no play and with only a very small amount they will fit. They simply open up, fit around the cable to be connected to and the new splice wire is inserted into the end of the connector and then it is squeezed using a pair of pliers. The small internal metal clip pierces both cables' insulation and makes the connection. They're actually pretty good especially if you fill them with grease. Just for info; BT use a connector which works in the same way but they are filled with silicon grease. Admittedly, they're usually inside a box but they last for years.

Cutting the cables and then resoldering is a fairly good alternative but you can't be sure that moisture won't creep down between the double section of cable since the shrink won't seal this. That is why I ensure there is a piece of self amalgamating tape between the cables as they are wrapped and that a small cable tie is used at each end to ensure the tape is well squeezed.

Just for a bit more info, water will find its way into and along the inside of cables. The story: I had a mysterious brown stain inside my boat engine compartment. It looked like rust but there was no sign of any rusting metal. The stain was sometimes damp. To shorten the story; much later I had a failure of an outside mounted trim switch and inspection of the failure showed water ingress. The screws used for the connectors inside the switch were steel. They had corroded badly and the inside of the switch was wet and brown. This was the source of the stain and the water made its way, through the cable, upwards and then over a meter before dripping a tiny drop at a time into the engine compartment from the spade terminal of the trim motor relay.

So, be advised to seal your cables well.
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Old 05 March 2008, 06:12   #14
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smart talk at last

Quote:
Originally Posted by jwalker View Post
It's rare there is no play and with only a very small amount they will fit. They simply open up, fit around the cable to be connected to and the new splice wire is inserted into the end of the connector and then it is squeezed using a pair of pliers. The small internal metal clip pierces both cables' insulation and makes the connection. They're actually pretty good especially if you fill them with grease. Just for info; BT use a connector which works in the same way but they are filled with silicon grease. Admittedly, they're usually inside a box but they last for years.

Cutting the cables and then resoldering is a fairly good alternative but you can't be sure that moisture won't creep down between the double section of cable since the shrink won't seal this. That is why I ensure there is a piece of self amalgamating tape between the cables as they are wrapped and that a small cable tie is used at each end to ensure the tape is well squeezed.

Just for a bit more info, water will find its way into and along the inside of cables. The story: I had a mysterious brown stain inside my boat engine compartment. It looked like rust but there was no sign of any rusting metal. The stain was sometimes damp. To shorten the story; much later I had a failure of an outside mounted trim switch and inspection of the failure showed water ingress. The screws used for the connectors inside the switch were steel. They had corroded badly and the inside of the switch was wet and brown. This was the source of the stain and the water made its way, through the cable, upwards and then over a meter before dripping a tiny drop at a time into the engine compartment from the spade terminal of the trim motor relay.

So, be advised to seal your cables well.
I work on the North Sea ( NL Coast Guard )for a couple decades and have helped and towed hundreds of boaters in trouble. Scotchblock and other el cheapo car rubbish is nice for the inland water sunlovers that never have any spray.
For serious boating in harsh environment use marine grade cable that is tinned inside, at least for the instruments you realy need.
I've seen serious electrical damage, even boats burn, because of too much resistance in (inside black copper strands) cables, wrong fused, too much weigt on cables hanging like spaghetty (the aforementioned cowboys )

I work with Ancor stuff and they recommend double crimp over soldering see FAQ's on their site.
Our ribs are 24/7 shaking and vibrating on a parent vessel in spray or dodge salt water when used. Me and my collegues put a lot of effort in keeping it clean and reliable. Scotchblock and anp connections are o.k. as a band aid but don't forget the serious repair
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Old 05 March 2008, 08:31   #15
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Well said. Certainly don't rely on automotive cable. It needs to be proper tinned marine grade. Moisture and corrosion will get in anywhere and turn your cable green and black. I don't solder the ends before crimping but I always use Ancor cable and crimps with heatshrink sleeving.
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Old 05 March 2008, 11:44   #16
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Since AndrewH's thread has turned into a general discussion of electrical wiring practice, here's a few things I found work and the reasons why.

I always solder connectors. If only a crimp is used and the cable does get water into it and corrode then each strand gradually becomes insulated from the others. This ensures that only the strands which are making contact with the crimp will carry the current. If the cable is properly soldered at each end, then the corrosion which just blackens the copper will have little effect.

I've found that on a soldered cable which then has a crimp fitted (not soldered) the crimp tends to slacken because the solder seems to creep with time. It appears to happen in domestic mains plugs too. When cables have soldered ends I've frequently found the screws slack after a period of time. Perhaps it depends on the grade of solder used.

Something else I do which is not generally done but it's always successful and has given me no trouble. When using screw terminals, as in a busbar, I strip the cable and fold it back along one side of the insulation. When entering the cable into the connector's hole the bare cable is placed away from the screw and the screw is tightened hard until it just pierces the insulation. This ensures: the cable strands aren't crushed and weakened by having a screw directly crushing them which is made worse by it's turning, a good connection is made and the cable outer takes the strain and absorbs any flexing. If there is more that one cable fitted into the same hole, I use a cable tie around them just outside the hole to strengthen the bunch.

I never rely on normal shrink tubing to keep the water out but I often use it as an insulator, though I usually use a double layer because its wall is pretty thin. Adhesive lined shrink is a different matter. If I use it, I use the largest diameter I can. This ensures the maximum wall thickness when shrunk and the maximum amount of adhesive to squish into any crevices.
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Old 05 March 2008, 12:09   #17
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I always solder connectors. If only a crimp is used and the cable does get water into it and corrode then each strand gradually becomes insulated from the others. This ensures that only the strands which are making contact with the crimp will carry the current. If the cable is properly soldered at each end, then the corrosion which just blackens the copper will have little effect.
I respectfully disagree. Soldering is used to make an electrical connection. It does not seal the conductor against water intrusion. To do that, you need something that coats the exposed conductor and/or solder joint, and seals to the insulation. If you don't, you'll get water ingress between the insulation and the conductor (soldered or not) and eventual corrosion of the copper inside the jacket.


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I've found that on a soldered cable which then has a crimp fitted (not soldered) the crimp tends to slacken because the solder seems to creep with time.
This is true. If you don't trust the crimp connection alone, crimp the bare wire, then solder the exposed conductor to the crimped terminal. Shouldn't be necessary, though. For waterproofing, use something like Liquid Electrical Tape, and throroughly cover anyplace the cable's conductor is exposed.


Note that the ABYC (American Boat and Yacht Council?) has changed their standard wiring practice to crimp only. They say that soldering causes a stiff section of wire that focuses flex in one point of the cable, and accelerates stress failure. The stiffening is not always located at the exposed solder connection but can also be a ways up the jacket; it's due to a couple of factors, but usually is caused by solder or flux wicking up between the conductor strands.

That said, I still solder connections. I find it easier to waterproof solder joints rather than crimp connections (though adhesive shrink tube crimp connectors are available.)


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Old 05 March 2008, 13:40   #18
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I respectfully disagree. Soldering is used to make an electrical connection. It does not seal the conductor against water intrusion.
jky, thanks for your comments but maybe I didn't express myself clearly because I wasn't suggesting that soldering made a watertight connection. I was suggesting that each strand of the cable would be linked at both ends and therefore be carrying current.

Quote:
Note that the ABYC (American Boat and Yacht Council?) has changed their standard wiring practice to crimp only. They say that soldering causes a stiff section of wire that focuses flex in one point of the cable, and accelerates stress failure. The stiffening is not always located at the exposed solder connection but can also be a ways up the jacket;
I agree with their findings but it is possible to have the best of both and I use silicon sleeving which is slid back along the cable to enclose part of the connector and provide the support necessary. Proper soldering technique will ensure that the solder does not travel more than a few millimeters from the joint. Though, there a many situations where the harness can be made in such a way that the cables are tied off to each other and the whole thing becomes fairly rigid and there certainly isn't going to be enough flexure to fatigue the cable.
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That said, I still solder connections.
I'm pleased to hear it.
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Old 05 March 2008, 14:19   #19
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Any connection should ideally be contained in an IP rated junction box.
Full immersion up to 1m is coded IPX7
splash proof is IPX4
waves IPX6 and
submersion IPX8, as per BS7671:2008

Check this page
http://www.screwfix.com/prods/15995/...f-Junction-Box
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Old 05 March 2008, 14:58   #20
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Any connection should ideally be contained in an IP rated junction box.
You obviously haven't seen under my dash.
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