Extending a cable with crimps

[Tricky Dicky]

When I re-site the CU the cable to the shower will need extending this will be a temporary measure until we do the bathroom following the kitchen. Once the bathroom is done this cable will be redundant, unfortunately part of this cable will be buried in plaster. I am hoping as it goes through the loft I can pull a few metres of new cable through. If I cannot replace the cable the join will be in an inaccessible place in the loft or buried in the plaster. Can I use crimps in either of these situations and what additional insulation do I need to use eg. heatshrink, self amalgamating tape or other?

Richard

[John Rumm]

Crimps and heatshrink would be the usual preferred option.

[The Natural Philosopher]

I have buried crimps in walls before.

Whether or not they are legal is open to question.

If wet plastering over, obviously waterporoof them

[newshound]

Mind you, my father used to replace the old round baekelite light switches with "modern" square ones without bothering with a metal box. He just made the hole large enough, wired them up, and then set them in polyfilla. Admittedly no RCDs in those days (mostly no earth either) but he never blew a fuse that way.

(There was, usually, only half an inch of wire available so limited scope for doing better anyway).

[Andrew]

10 mm cable though ??

[John Rumm]

Large crimps, and a bigger crimp tool...

However sometimes with a bit of lateral thought, you can change the problem enough to make another solution more appropriate.

Say for example, pulling the cable to the shower back from the old CU into the loft, and pulling in a new section of cable from the new CU to the loft. Then you can use a large high capacity JB in a location that

*is* accessible to join the cables, and all you need bury in plaster is a bit of the new cable.

[John Rumm]

It would be close to impossible to blow a fuse in those circumstances. There is typically no neutral at the light switch position, and on an unearthed circuit, there is nothing else you could sink enough fault current to blow the fuse.

Best you can normally do is to over sleeve the old rubber insulation, and crimp on an extension to give you bit more wire to play with...

[Chris Green]

Big crimps and heatshrink. :-)

You do need a serious crimp tool for larger than 6sqmm though, standard insulated crimps and ratchet crimp tool only go up to 'yellow' which is 6sqmm maximum.

For larger stuff I have a hydraulic crimp tool which goes up to

65sqmm. For a one-off job it might not be worth it. You can get mechanical crimp tools for these larger sizes but they're still quite expensive. I guess you could do it with a vice/hammer plus punch but I'm not sure how good the result would be.

[Andrew]

Problem is, a racket crimper for 10mm is going to cost upwards of £40, and you could get 15 mtres of 10mm t&e for that price.

[harry]

You can join cable with solder ferrules. (A tube in which cables are soldered using a blowlwmp) No crimping tool needed. All sizes of cable can be thus joined.

[John Rumm]

Indeed, hence other options... although you do get the keep the crimper for next time!

As a one off, you may be better using solder and heat shrink (although you will probably need small flame to get enough heat into 10mm^2)

[Tricky Dicky]

The present cable is only 4mm2 my preferred option is to pull a length of new cable through using 6mm2 which I will also be using elsewhere. The problem with accessibility is that the roof pitch is only 22° and trussed and guess where the cable runs - a real test for claustropobia. At the bathroom end it terminates at a ceiling switch, if I am to join it will be in the wall above the CU. At the moment I have no idea if the existing cable will pull through but if it will I will use it to pull through a new length.

As I said before this is a temporary arrangement so we can use the shower until the bathroom is replaced. The present shower will be replaced with a digital shower which is basically a mixer and does not heat the water so the present supply cable will be left in situ and terminated off when no longer required.

Richard

[FMurtz]

We were taught to splice cables and then solder.

[Steve Walker]

That's what children are for! Seriously, I suffer from arthritis and crawling around is very painful and affects me for days, so my eldest son gets sent under the floor or in other difficult to access places when pulling cables.

SteveW

[John Rumm]

I suffer from being too big, but have discovered that son can be bribed to slip between joists and descend under floors etc! :-)

[newshound]

No crimps in those days, this was before he bought me our first electric soldering iron (a second hand Henley Solon 25 watt) in about 1963. Although we had a tin-man's one that you heated on a spirit stove or gas ring. :-)

[charles]

If you aren't careful you melt the insulation,

[The Other Mike]

In the main these sleeves are used for connecting earthing pigtails onto screened signalling cables.

Whilst they can join large diameter cores they are not specifically tested nor certified by the manufacturer for carrying any level of current.

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[harry]

Of course they are. The underground electricity distribution system depends on soldered joints. On aluminium as well as copper cables. I spent years installing them.

[The Other Mike]

Harry those you refer to are from different manufacturers, with them specifically designed and certified for purpose methods of creating joints to carry large currents. Jointing now heavily relies on crimps, rather than sweated joints, even with 800mm^2 conductors

The ones you linked to would expressly not be permitted on any electrical substation anywhere in the UK network for the purposes of carrying anything other than stray currents on a signallng cable screen. Like I said that IS precisely and exclusively what they are used for here, right now.

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