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.

 

[pc1966]

In theory crimps are great, and certainly are acceptable for maintenance free connections, extending earth bond wires, etc.

In practice though not all of them are suited to single strand wire (like 2.5mm T&E, for example), as mostly they are intended for stranded wire (both 7 strand like conduit wire, and finer like tri-rated or automotive wires).

So unless it is a crimp designed for the type of wire you are using, and properly crimped using the matching ratchet tool (or fancy hydraulic ones, etc), you would be far safer to use the likes of the Wago MF free box & terminals, checking carefully what it needs to be MF in practice (they often specify a cable tie as well as the clip-in lid, etc).

 

[davesparks]

Crimps, properly fitted, make a very good connection.
Yes standard blue crimps are a good method of jointing stranded conductors, subject to being fitted correctly using the correct size crimp, correct tool etc (but that is true of any connection)

However most standard red/blue/yellow crimps are not suitable for solid core cable, such as 2.5mm T&E, this may be what your lecturer was referring too.

Crimping generally is the preferred method for connections once you get into the bigger sozes/higher current connections.
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So unless it is a crimp designed for the type of wire you are using, and properly crimped using the matching ratchet tool (or fancy hydraulic ones, etc), you would be far safer to use the likes of the Wago MF free box & terminals, checking carefully what it needs to be MF in practice (they often specify a cable tie as well as the clip-in lid, etc).

How are do you suggest the OP mounts a wago box to the steel trunking?

I see no reason why a wago box would be better than a steel box mounted to steel trunking, I'd say it is a poor alternative.

 

[pc1966]

How are do you suggest the OP mounts a wago box to the steel trunking?

Err, with screws through trunking to the wall holding trunking behind it, or nuts/bolts to top/bottom of trunking if accessible/preferred, same as you would mount a metal box?

I see no reason why a wago box would be better than a steel box mounted to steel trunking, I'd say it is a poor alternative.

Do you mean a joint box outside the trunking?

When I have done it the Wago box was comfortably smaller than the 50 x 100 trunking and fitted inside, has compartments to hold the Wago terminals, etc.

 

[Dustydazzler]

We used to regularly join cables using blue and yellow crimps , but as soon as wagos hit the wholesalers shelves we pretty much were converts overnight...

 

[davesparks]

Err, with screws through trunking to the wall holding trunking behind it, or nuts/bolts to top/bottom of trunking if accessible/preferred, same as you would mount a metal box?


Do you mean a joint box outside the trunking?

When I have done it the Wago box was comfortably smaller than the 50 x 100 trunking and fitted inside, has compartments to hold the Wago terminals, etc.

Ok so you bolt the wago box to the trunking, but how do you get the cables into it? There no way to attach with a bush and lock ring.

Of course I mean outside the trunking, everyone knows you avoid joints inside trunking as far as possible. And you certainly never mount a box inside trunking!

Why on earth would you fit a joint box inside trunking? All that's going to do is really ---- off the next person trying to install a cable in the trunking!

 

[Dave OCD]

In this scenario I'd much rather use Wago or Ideal 32amp rated push connectors within the galvanised box. No requirement whatsoever for it to be a 'maintenance free' assembly if it's accessible. I'm not keen on those red/blue/yellow through crimps as there are a lot of cheap rubbish versions out there.

 

[David345]

In theory crimps are great, and certainly are acceptable for maintenance free connections, extending earth bond wires, etc.

In practice though not all of them are suited to single strand wire (like 2.5mm T&E, for example), as mostly they are intended for stranded wire (both 7 strand like conduit wire, and finer like tri-rated or automotive wires).

So unless it is a crimp designed for the type of wire you are using, and properly crimped using the matching ratchet tool (or fancy hydraulic ones, etc), you would be far safer to use the likes of the Wago MF free box & terminals, checking carefully what it needs to be MF in practice (they often specify a cable tie as well as the clip-in lid, etc).

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.

 

[lozarus]

In practice though not all of them are suited to single strand wire (like 2.5mm T&E, for example), as mostly they are intended for stranded wire (both 7 strand like conduit wire, and finer like tri-rated or automotive wires).

Agree entirely - it's a real bone of contention for me that they were included in 17th as an approved MF joint. There's too many variables in the style of tool available to crimp them, to the quality of the crimp itself. I mean you can go to Halfords and buy some blue crimps - but I wouldn't even use them on the car as the quality of those particular ones are so poor. I would argue that it could be easier for many to make a sound joint with a typical bakelite junction box than with a through crimp (particularly for people newer to the industry) - that said I haven't used a traditional unction box for years, I'm also a wago / Hager MF user - but even with wago, to actually properly comply with MF requirements requires some very specific rules to be followed (even down to the cable tie on the correct wagobox, and then you have the aggregate current bit) - I've seen many well versed electricians using wago as MF - but unbeknownst to themselves not actually in a fully compliant fashion - in short it's all far too complicated

Sorry got a bit off topic - yes fine if done properly but they're hard to do properly, especially in tight spaces and especially with single strand t&e. A place I used to work at extended old rings into dado with them as the proprietary connector - I'd say 50% of them failed at some point or another. A lot of the old skool swear by them though

 

[davesparks]

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.

Screwed connections are generally avoided for joints these days, Wago's or similar are generally the most popular with crimps also being compliant.
This is not to say there is anything particularly wrong with screw type connections, they are just becoming less popular

 

[David345]

Yeah sorry when I said steel box I mean't steel joint box. I just forgot the name

 

[davesparks]

Agree entirely - it's a real bone of contention for me that they were included in 17th as an approved MF joint.

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!
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Yeah sorry when I said steel box I mean't steel joint box. I just forgot the name

Usually it would be either an adaptable box or conduit box (aka BESA box)

 

[David345]

Screwed connections are generally avoided for joints these days, Wago's or similar are generally the most popular with crimps also being compliant.
This is not to say there is anything particularly wrong with screw type connections, they are just becoming less popular

And using crimps I would say would increase resistance in the conductors. Therefore increasing the Zs readings.

 

[davesparks]

And using crimps I would say would increase resistance in the conductors. Therefore increasing the Zs readings.

Only if the joint is made badly. A badly made joint of any kind will increase resistance and cause heating of the joint.
A skilled electrician will be able to make a good joint in conductors using the variety of methods available.

Screwed connectors can be prone to problems with stranded cables as the screw tends to spread the strands not properly clamping them, also the screw can cut through some strands.

 

[David345]

Only if the joint is made badly. A badly made joint of any kind will increase resistance and cause heating of the joint.
A skilled electrician will be able to make a good joint in conductors using the variety of methods available.

Screwed connectors can be prone to problems with stranded cables as the screw tends to spread the strands not properly clamping them, also the screw can cut through some strands.

Ahh right makes sense