Joining a cable to be buried in a wall

[SJD]

Now and again, I need to join a cable that is buried in a wall, sometimes in a stud wall, sometimes to be plastered over. Sometimes when someone has drilled through it (last one was a kitchen fitter who should have known better), or sometimes to extend a cable e.g. to move an accessory lower on the wall. Generally I'm thinking of 2.5mm2 or 1/1.5mm2 twin & earth. And assuming a new cable can't easily be pulled through.

What jointing method do people prefer?

I've used heatshrink crimp butt connectors plus an outer covering of glue-lined heatshrink. I worry about the crimp not gripping one of the conductors tightly enough and it coming loose.

I've also used heatshrink solder connectors, again with an outer glue-line h/s covering. If the copper is not clean enough, I worry about a dry joint to one of the conductors.

And what if one cable is new solid T&E, while the other cable is stranded imperial cable?

 

[Rpa07]

Own solder fed in. I originally took the insulation off of insulated butt crimps and soldered because I didn't trust the crimp itself, now I've got so used to the 'ritual' that I just get on with it. I found a good source of non insulated through crimps.
To the other question, I use a creme brule blowtorch to shrink the wrap. Have to be a bit careful in tight spaces but may try a heatgun in future.

 

[Rpa07]

Own solder fed in. I originally took the insulation off of insulated butt crimps and soldered because I didn't trust the crimp itself, now I've got so used to the 'ritual' that I just get on with it. I found a good source of non insulated through crimps.
To the other question, I use a creme brule blowtorch to shrink the wrap. Have to be a bit careful in tight spaces but may try a heatgun in future.

 

[Rpa07]

Own solder fed in. I originally took the insulation off of insulated butt crimps and soldered because I didn't trust the crimp itself, now I've got so used to the 'ritual' that I just get on with it. I found a good source of non insulated through crimps.
To the other question, I use a creme brule blowtorch to shrink the wrap. Have to be a bit careful in tight spaces but may try a heatgun in future.

I think I've been sucked into the double post issue! It posts but leaves the post to make you think it hasn't been. I thought you were all just careless!

 

[Rpa07]

Oh no, it ended up three! I'm so embarrassed!

 

[SJD]

Thanks for all the replies. I perhaps should have clarified that my question was for when it is not easy to access the floor/ceiling void and the customer doesn't want an extra blanked-off accessory box.

I agree with Pete999 that burying a Wagobox under plaster would be rough old job, perhaps why I'd not thought of doing so.

I hadn't thought about enclosing the SpliceLine connectors in some heatshrink, not sure that is also not a bit rough too.

The connectors in Midwest's photo, I've used quite a few times, generally successfully though is it possible to burn the sleeving if too enthusiastic with the heat gun.

As an aside, I thought after a new post I was going to loose the irritating ad at the top of every page, but it still malingers there ...

 

[Rpa07]

We don't mind an ulterior motive @SJD - it's amazing how you look past the ads as if they are supposed to be there.
Ps I've never written ulterior before in my life, took me a good 30 seconds to spell it and that's with the tech!

 

[Wilko]

Can I be less popular ? ... heat shrink is great, but if it's the stuff I think we all use, as far as I know its not BS rated for cable insulation. Doesn't mean it doesn't work, but 2 layers of heat shrink is not the same insulation as a BASEC 6004 cable (624Y for example). So I think the joint still needs a containment ... I can hear rocks hitting the roof already

 

[SJD]

Own solder fed in. I originally took the insulation off of insulated butt crimps and soldered because I didn't trust the crimp itself, now I've got so used to the 'ritual' that I just get on with it. I found a good source of non insulated through crimps.

Thanks, I'll perhaps give this a try next time.

 

[davesparks]

Can I be less popular ? ... heat shrink is great, but if it's the stuff I think we all use, as far as I know its not BS rated for cable insulation. Doesn't mean it doesn't work, but 2 layers of heat shrink is not the same insulation as a BASEC 6004 cable (624Y for example). So I think the joint still needs a containment ... I can hear rocks hitting the roof already

Interesting point, I'd have to look at the label the next time I buy some to see what it is or isn't approved to.

DNOs make extensive use of joint kits which are insulated and sheathed with adhesive lined heatshrink somclearly a suitable product exists,

 

[Deleted member 9648]

Personally I would never bury a joint of any sort in the wall. I always either replace or use a flush box and blank plate.

 

[SparkyChick]

If you're soldering and you're concerned about dry joints caused by dirty or oxidised cables, get yourself a flux pen and dab a little on the copper before soldering. Can help immensely.

 

[SparkyChick]

And a side note about using blowtorches... make sure your insurance covers you for using them. When I took out mine, I was asked about hot tools, which included blowtorches, and whether I used them. I have a heat gun for shrinking which doesn't fit the hot tool category because it doesn't use flame.

 

[SJD]

If you're soldering and you're concerned about dry joints caused by dirty or oxidised cables, get yourself a flux pen and dab a little on the copper before soldering. Can help immensely.

Is this the same as the tub of flux I use whenever I do a bit of home DIY plumbing and solder some copper pipes?

And a side note about using blowtorches... make sure your insurance covers you for using them. When I took out mine, I was asked about hot tools, which included blowtorches, and whether I used them. I have a heat gun for shrinking which doesn't fit the hot tool category because it doesn't use flame.

I did once try to use a small blowtorch with an attachment but didn't get it to work properly, so I stick with an electric heat gun, which I much prefer. The only downside is the times when there's no convenient socket nearby due to the work underway!

 

[SparkyChick]

Is this the same as the tub of flux I use whenever I do a bit of home DIY plumbing and solder some copper pipes?

Not sure about chemical composition, but I suspect the paste is somewhat more aggressive. The flux pens I use are designed for printed circuit board work, like mounting surface mount devices in hot air rework scenarios.

I did once try to use a small blowtorch with an attachment but didn't get it to work properly, so I stick with an electric heat gun, which I much prefer. The only downside is the times when there's no convenient socket nearby due to the work underway!

Granted if the whole house is off it's a bit tricky, but my long extension lead and heat gun travel together

 

[Wilko]

And a side note about using blowtorches... make sure your insurance covers you for using them. When I took out mine, I was asked about hot tools, which included blowtorches, and whether I used them. I have a heat gun for shrinking which doesn't fit the hot tool category because it doesn't use flame.

Thanks for that SC ! I was practicing my "really Sir, it's just my hair dryer" speech but it looks like I can bring it out of the closet now

No Westie, the heat gun, the heat gun ...