UK Are blue through crimps allowed on ring circuit.

[David345]

I'm a trainee electrician and I was working with a qualified electrician extending a 32A ring circuit and we were using 2.5mm single conductors (CPC was 2.5mm aswell) going through PVC conduit and then going through steel trucking.

And to connect the old ring conductors with the new extended ring conductors the electrician used blue through crimps to crimp the new and old conductors together in a small separate steel box connected to the steel trunking.

I said to him aren't you supposed to connect them together in some kind of juction box instead for a better strong connection and he said you don't need to.

So I was wondering if using blue crimps or just crimps in general to connect conductors together is ok and within the regs because I'm sure one of my college lecturer told me a few years ago that you can't do that.

I'm just curious is this allowed or not.

Thanks.

 

[lozarus]

What would you replace crimped connections with in the regulations? Bearing in mind that crimped connections are the only realistic option for an MF joint in the majority of cable sizes, wagos don't go past 6mm!

Again it's an individual thing - but my point is that crimps mainly seem really suited to stranded cables and are available in such varying quality that there's a lot of room for error. I think this trend should have been realised when 17th was established by wider study. At that point an alternative could have been established - what it is, I don't know.

 

[davesparks]

Ahh right makes sense

Again it's an individual thing - but my point is that crimps mainly seem really suited to stranded cables and are available in such varying quality that there's a lot of room for error. I think this trend should have been realised when 17th was established by wider study. At that point an alternative could have been established - what it is, I don't know.

Yes crimps are generally suited to stranded cable, and the vast majority of cables that we use are stranded.

The regulations require good workmanship an dpriper materials to be used, this addresses the use of poor quality materials or workmanship.

Exactly, there isn't a suitable alternative once you get out of the small sizes. For small sizes wagos and their equivalents are a suitable alternative.

Last week I had to joint a 25mm cable, I used through crimps because that's what was best suited to it as far as I am concerned. Soldering was not an option as it woukd take longer to get the hot works permit than do the job, shear bolt connectors would be too expensive and not so easy to insulate once connected.

 

[David345]

Again it's an individual thing - but my point is that crimps mainly seem really suited to stranded cables and are available in such varying quality that there's a lot of room for error. I think this trend should have been realised when 17th was established by wider study. At that point an alternative could have been established - what it is, I don't know.

I'd like to say as well. I assume you wouldn't crimp stranded conductors and lay them directly inside steel trunking which has already got loads of other stranded conductors inside, as this would increase the chance of someone accidentally pulling apart a crimped conductor if they were pulling old conductors out for example. You would most definitely have to put the crimped conductors in a separate steel joint box.

 

[ipf]

Well the electrician did use proper blue through crimps and a sort of higher quality than standard crimp tool to crimp the conductors together. Its just I thought it just looked very unconventional. You could probably pull them apart if you used some force which would be much harder if the conductors were connected tightly using screws in a junction box.

I wouldn't like to think ANY crimp that I've ever installed could be pulled apart, physically. That's the idea of them...a permanent connection.

 

[David345]

Yes crimps are generally suited to stranded cable, and the vast majority of cables that we use are stranded.

The regulations require good workmanship an dpriper materials to be used, this addresses the use of poor quality materials or workmanship.

Exactly, there isn't a suitable alternative once you get out of the small sizes. For small sizes wagos and their equivalents are a suitable alternative.

Last week I had to joint a 25mm cable, I used through crimps because that's what was best suited to it as far as I am concerned. Soldering was not an option as it woukd take longer to get the hot works permit than do the job, shear bolt connectors would be too expensive and not so easy to insulate once connected.

Did the 25mm through crimps have insulation around it or was it one of those crimps that don't have Insulation around it (such as all exposed metal) and/or did you incase the crimp joint in a joint box or junction box?

 

[ipf]

I'd like to say as well. I assume you wouldn't crimp stranded conductors and lay them directly inside steel trunking which has already got loads of other stranded conductors inside, as this would increase the chance of someone accidentally pulling apart a crimped conductor if they were pulling old conductors out for example. You would most definitely have to put the crimped conductors in a separate steel joint box.

....and that's absolute rubbish......crimp and heatshrink, no problem.
Generally you're talking about repairing damaged cables or mistakes installing, though. If you're jointing for a further cable, then always an external box. Available length dependant.

 

[David345]

....and that's absolute rubbish......crimp and heatshrink, no problem.

Not to be rude but aren't heatshrink a bit outdated? And doesn't really look great.

 

[ipf]

Not to be rude but aren't heatshrink a bit outdated?

What? Like pyro you mean?
Heatshrink is vital for some repairs.

 

[David345]

What? Like pyro you mean?
Heatshrink is vital for repairs.

No thats totally different. I mean't the concept of heatshrinking conductors Inside some steel trunking

 

[davesparks]

I'd like to say as well. I assume you wouldn't crimp stranded conductors and lay them directly inside steel trunking which has already got loads of other stranded conductors inside, as this would increase the chance of someone accidentally pulling apart a crimped conductor if they were pulling old conductors out for example. You would most definitely have to put the crimped conductors in a separate steel joint box.

If the conductors can be pulled out then the joint is bad.

Joints inside trunking are not ideal due to the damage it would cause if the joint does fail.
If a crimp joint has to be in trunking for any reason then I would insulate it with heat shrink.

 

[Darkwood]

Your bog standard red,yellow and blue insulated through crimps are for stranded cable and should not be used on solid as mentioned earlier, crimping solid requires a different crimping tool and crimp to make a sound reliable joint and if you have a ranger of crimping tools you'll tend to find solid cores are crimped with indent crimpers but there are exceptions that doesn't warrant a mention in this context.
Using the wrong crimp and crimper on a specific cable can and often will lead to deformed crimps thus a bad joint however tight it seems to be, one has to remember that other than the usual working load these connections need to tolerate they also need to withstand a possible 1000+ amps of fault current too.

 

[telectrix]

with uninsulated crimp connectors, I'd expectto see heat shring sleeving applied over the crimp. sod fitting boxes. waste of effort . a joint of any description, if done properly with the right parts and the right tools, is a good joint.

 

[David345]

with uninsulated crimp connectors, I'd expectto see heat shring sleeving applied over the crimp. sod fitting boxes. waste of effort . a joint of any description, if done properly with the right parts and the right tools, is a good joint.

Fair enough that actually makes sense now with the heatshrink. My bad. I dont have so much experience in the electrical Industry as I'm still a trainee.

 

[ipf]

with uninsulated crimp connectors, I'd expectto see heat shring sleeving applied over the crimp. sod fitting boxes. waste of effort . a joint of any description, if done properly with the right parts and the right tools, is a good joint.

Nice heat gun though, tel.......that cig lighter's not up to it nowadays.

 

[Lucien Nunes]

Collecting some comments from above:

Joints correctly and skilfully made using proper materials appropriate for the application, are good joints. It matters not whether they are Wagos, screw terminals, inline crimps, crimped lugs on a stud, soldering or whatever, unless you have to meet a specific standard that is more prescriptive (e.g. for ATEX or MF situations). As Davesparks points out (and I regularly point out to anyone who will listen) a good electrician can make a sound joint with any suitable material. Making connections is one of the most fundamental skills an electrician can have, which used to be taught in great detail but now seems to have fallen by the wayside. But it is a skill, not just a list of do's and dont's like: 'Blue crimps are OK for RFC's.'

There are many bad / unsuitable materials and unskilled persons out there. The dodgy insulated crimps from the car shop, the guy who has good crimps but uses a duff crimp tool, the numpty who crimps them with pliers and his mate who uses stranded-only crimps on solid conductors. The regs don't call these out specifically, because there is the overall requirement for proper workmanship and materials which covers it.

Crimping, using good materials correctly installed, is reliable and secure. If a cable can be pulled out of a normal crimp without damaging / stretching the rest of the cable, it wasn't properly installed. If I crimp a ring to a 2.5mm² tri-rated, put the ring in the vice and pull, the cable rips apart leaving strands still stuck in the terminal. Any good connection will not add measurable resistance, otherwise if it carries more than a whiff of current, it will overheat. A connection that does not overheat is not however automatically to be considered a good one, as it might fail with time or movement in a way that it should not.

Additional insulation (and sometimes even basic insulation) is sometimes required to complete a joint or make it suitable for the installation conditions. Heatshrink of the right type is a versatile material for many kinds of joint. Applying insulation requires skill and knowledge to ensure that it is adequate, e.g. of the same strength and durability as cable insulation. Just putting any random kind of heatshrink over an uninsulated crimp is not in itself adequate.

Personally, I'm not too fussed about properly made inline joints with suitably robust insulation lying within trunking. If there are many joints, or the trunking is very busy, or there is a reason for them to be vulnerable, then a terminal box is needed. Bare blue butt crimps are not quite up to the mark.

Perhaps I should run a course. 'From blue butts to bellhangers in 10 easy lessons.'