What colour crimp for ring mains?

[KPaul]

Hi all,

A couple of weeks ago I had a professional sparky extend a couple of spurs so that I could move some sockets around. He was a decent chap and did the job for what I though was a decent price (£60).

My question is that after doing some reading I found out that blue butt crimps should be used for such a purpose but I'm pretty certain that the sparky used yellow. Is this okay? I know yellow are higher rated but aren't they for a bigger cable? I can't have a look now as the cables are hidden behind a stud wall.

Am I worrying about nothing and should I just put my trust in the sparky?

Cheers,
Paul.

 

[Chri5]

Blue for LN 2.5mm cores, red for 1.5mm earth / cpc

Yellow for 4mm cores, then again he could have crimped them in the blue jaw of the crimper.

A bodge, but it should be ok- did he offer up a certificate or test the circuit ?

 

[KPaul]

He did offer a certificate and he said he'll come back and put the sockets in and test them for me. For all I know he did crimp them in the blue jaw, I didn't see that part. Should I bring it up with him when he comes back? It's not fixable without ripping down two brand new & plastered stud walls and loads of insulation.

I know I'm going to worry myself over this question, but what's the worst that can happen if he has used the wrong ones? I did see that he staggered the joints and used insulating tape afterwards, followed by capping and cable clips.

Cheers,
Paul.

 

[Click-Sure]

Crimping a yellow crimp in the bule jaws of a crimper just wrecks the crimp and doesn't do much good to the crimper.

Crimping 2.5mm2 wire in a yellow crimp with the yellow jaws does hold, but not as well as a blue crimp, which is designed to hold.

The issue of cables enclosed in thermal insulation raises its ugly head here too.

 

[KPaul]

So what do I do from here then apart from rip down the wall which I just can't bear to think about? I may be wrong about the yellow crimps but I'm pretty certain they were.

And as far as the stud wall being insulated - I did also explain this to the professional who didn't seem phased by it. Seeing as it's a spur can I not just limit what I plug into it to keep the heat down? It's probably going to be a fish tank or digital piano....300 watts max.

Why is it acceptable to plaster in cable that's not in conduit/capping (as I have been informed by a sparky in a different thread) yet it's not acceptable to have a cable nailed to a brick wall with 3" of insulation covered in plasterboard? I would have thought the air would circulate better around the latter?

Please help as I know I'm going to lose sleep over this one....

Paul.

 

[Taylortwocities]

He may have doubled over the 2.5mm and then crimped that in a yellow butt connector. That does make a very secure crimp joint.

 

[KPaul]

I've been looking at some figures for cabling and found out that running a cable in brickwork, plaster, etc will have a capacity of 27 amps. In insulation above 100mm then it's 17 amps, but I've only got 75mm of insulation under plasterboard and therefore the capacity of the cable will be 21 amps (and the insulation isn't sitting on top of the cable as in loft insulation).

Correct me if I'm wrong (and please do) but I thought this will be okay for three reasons:

- this is a spur and only feeds one double socket and therefore the ring mains isn't passing through the insulation. The only current running through this cable will be what I run off the socket. I could run two hairdryers and still be okay surely? (Not that I ever will! 500w tops)
- if an appliance that is plugged into this socket goes faulty and draws too much power then the fuse of the appliance will pop leaving the mains cable safe.
- I thought there was a general rule that the cable must be at least two thirds of the main fuse and therefore if this cable was to cause an issue surely the main 32 amp fuse will still go before the cable does?

Please believe me when I say I'm not going to risk anything. I've decided to put my trust in the original sparky and the way he connected the cables using the crimps - I made sure he was part P before I contacted him. I'm actually more interested in how it all works than worrying about it now. If I hadn't read any information at all and was your typical homeowner then I wouldn't think any different at all!

Now this next question will make you all go "and that's why you're not an electrician" but I will ask it anyway.....if a cable's capacity is 21 or 27 amp then surely it won't actually burn out at these capacities? These are the "safe limits" aren't they? The main fuse is rated at 32 amps and will surely burn out way before these cables do (even though it's rated a lot higher)....that's the whole point isn't it? I never realised there was so much maths with being an electrician!

Paul.

 

[KPaul]

Sorry correction....main fuse is re-wireable and is 30 amp.