Joining mains cable with crimps

[Lobster]

I have to extend an existing 1.5mm cable which feeds a light fitting, which (she says) needs moving. I'm intending to use crimps; never having done ths before I'd just like to confirm the methodology first.

I have some blue butt crimps and a ratchet crimping tool; I believe the whole lot needs encasing in heatshrink too? What I've not been able to ascertain is whether each individual crimped wire needs separately encapsulating (despite no bare copper being visible) or do you have to sheath the whole shebang? Or both? If not, when do have to and when do you not?

Finally, what diameter heatshrink do I need to buy for this application (and also for joining 2.5mm cables, while I'm at it...)

Thanks David

[rob]

I was always told not to use crimps on a single conductor cable, A junction box would be a better solution. Rob

[Al Reynolds]

Not if it will be inaccessible later e.g. buried in plaster.

Heatshrink-wise, see:

(short link : the strength of this I decided to only sleeve the whole thing in adhesive heat shrink. This is a lot less complicated, as it happens. I used: (short link : think I used the largest of these - they shrink quite a bit, and they need to be big enough to get over the crimps in the first place.

HTH, Al

PS It's a good idea to practice crimping on some spare cable. Don't be afraid to give the connection a good yank - if it comes apart then you're not doing it right. If some conductor is exposed at the end of the crimps, bear in mind this might just be the sleeve on the conductor moving.

PPS

(short link : might also be useful.

[Ed Sirett]

Someone will correct me if I'm wrong but I'm fairly sure that you use the red crimps on 1 and 1.5mm² and the blue on 2.5mm².

You can use a junction box as an enclosure for the crimped section to avoid heat shrinking. If you use proper insulated crimps then there will be no copper showing at all but the wires still need mechanical protection where there is no sheath.

[Andy Wade]

Either red or blue should be OK on 1.5.

Red: 0.5 - 1.5 mm^2 Blue: 1.5 - 2.5 mm^2 Yellow: 4.0 - 6.0 mm^2