Crimping for beginners

12 Oct 2013
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United Kingdom

I want to extend some 2.5mm t+e and 1.5mm three-core and earth cable in a joist void between upstairs and downstairs in my home.

I can't provide any access once I put the plasterboard back, so I understand the only permissible way to extend is to crimp the wires.

I've never done this before (I've only used junction boxes up in the loft). Do the standard DIY suppliers (Homebase/Wickes etc.) do a crimping kit for beginners?

Are there standard fittings and tools for this job? Would you have any tips for a crimping noob?

Thanks in advance

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Have you considered using 20 or 32 amp maintenance free junction boxes?

Hager do them.

This will probably be a better job and easier for you, rather than crimping.

Sounds interesting, I'll investigate. How do they differ from a 'normal' junction box? To be honest, I don't currently understand how a standard jb might require maintenance and hence require access. Can you shed any light on this?

Thanks, by the way.


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The Hager maintenance free junction boxes look just the job to me. Looks like I won't have to learn about crimping after all.

Screwfix don't appear to sell them. Can anyone here recommend a supplier?



Another question: I've been having a look at the Wago boxes and the push-fit connectors that go in them. They don't seem to be rated by ampage. Will the same connector work for 20A and 32A?


If you use the wagobox enclosures they have a table on paper inside telling you the rated current for each connector when used maintenance free, plus the total rating for all connections something like 50a. They are easy enough to use and cost isn't prohibitive.
They use the spring loaded connectors so shouldn't have any issue with solid cores or t&e of any kind.
They are reasonably bulky though, so take that into account.
They use the spring loaded connectors so shouldn't have any issue with solid cores or t&e of any kind.

But how long will they last? The spring force will decrease over time. There's already a few failures of Wagos a few years in causing melting.

IMO crimping or soldering is still a better job for properly inaccessible connections.
Any connection may fail, the ideal is a single cable from A to B.
I'm sure there's anecdotal evidence of failures but for me the selling point is it's hard to get it wrong and you don't need special tools.
With crimping there's loads problems possible if you don't do it right.
Soldering would be OK for me as it's easy to inspect when you finished, but you'd still have to heat shrink it afterwards. But if you need a compact joint it's the best. There is a slight risk of it melting when used in double fault situations, I think flameport has a video of overloading various connectors bit he didn't include soldered. The result was the wire was red hot before any connections failed.
I get your points John and agree - they are quick and require no skill. I have doubts over the longevity of maintenance free connectors though and I would be surprised if we don't see a load of problems 15 years. Some of the push-in connectors feel very flimsy when new and allow the conductor to freely rotate.
The terminals themselves allow the core to rotate, but you should either have strain relief or clip the cables so they won't move anyway.
The only movement should be thermal and seasonal, which the spring should deal with. The spring isn't some coiled slinky style spring like you get in those cheap pens, it's a flexible piece of metal that's designed to stay within it's elastic and fatigue limits.

I admit and agree it seems intuitively insecure (as do push fit plumbing) but that's the whole point of scientific method of design, they design things using appropriate materials and processes test them and tell us whether they meet the standard.
If they do then we can still distrust them but at the end of the day that's down to our level of cynicism.

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