EN60204 and twin ferrules

Yes Jam of course it is, the size is for two wires, although these may be of differing sizes, but is generally the overall cross section. As the only terminal connection is to a single piece of copper (the ferrule) I cannot see how anyone could claim this is somehow TWO, conductors! I could of course join the two conductors to a single one away from the terminal with perhaps a solder sleeve, but this is clearly daft. Many "standards" have this kind of ambiguity, that is why BS7671 has quite a lot of definitions at the front, attempting to make it as clear as possible, and to reduce (nearly works) interpretation.

I think that it's rather a shame that the standards organisations don't publish (as far as I know) official clarification documentation after the publication of a standard which is (perhaps inevitably) found to be ambiguous, unclear or otherwise in need of clarification. After all, with the best will in the world it's a pretty tall order to make a standards document absolutely bombproof and perfect. Some would argue that the notion of producing a standards document (particularly those of a relatively complex nature like 60204) which does not need any further clarification is a overly ambitious endeavour.

A somewhat different stance seems to be taken by the European Commission in respect of the various EU Directives. Some while ago I obtained a couple of publications published by them: "Useful facts in relation to the Machinery Directive 98/37/EC" (266 pages) and "Comments on Directives 98/37/EC" (269 pages). I know these now relate to a supersede Directive but I assume that updated versions of the documents still exist. Both documents are immensely useful and packed full of explanations, clarifications and lots stuff which assists a mere mortal to become confident that he's done his (or her) compliance job adequately well. Similar documents (which could perhaps grow as clarifications were made) for 60204 would be a immensely useful (especially if they mentioned twin ferrules).

Knowing that the EU documents existed was part of my reason for my original post here. I was hoping that an official standards clarification resource might be offered up by someone.

David Stone said:

bootlace simply holds the fine wires of 2 or more (given suitable size)

Sorry David, I fully disagree with the extremely poor practice of trying to cram more conductors into a ferrule than it's designed for.

Definitely only 2 of the correct size in a twin, without deforming the plastic insulating entry sleeve (and hence putting pressure on the conductors). Note you MUST have the correct metal tube size for the combined csa of the conductors (not too big, not too small) - and that's what causes the issue with insulated ferrules.

Example - it might seem logical that 4 no. 1.25 sq mm conductors might be brought together into a 2 x 2.5 sq mm ferrule (and I've indeed no problem with the basic concept, as the ferrule metal tube size is perfect for the job). However, the overall diameter (including insulation) of a 2.5 sq mm H05V-K tri-rated conductor is 3.3 mm, whereas the 1.25 is around 3.15 mm.

So, you can immediately see the problem, that if the inside of the plastic sleeve is a rounded rectangle with internal dimensions around 3.5 x 6.8 mm, there's no way you can ever squeeze 4 no. insulated 1.25 sq mm conductors in there.

The 1 x 4.0 sq mm has almost the same metal tube diameter as a 2 x 2.5 sq mm ferrule, but again you will struggle to get 4 no. 1.25 sq mm H05V2-K tri-rated singles into the 4.8 mm internal diameter plastic entry sleeve. 


I could see how this might work with bare (uninsulated) ferrules, if you matched the tube size properly to the overall csa of copper, but some copper would need to be left showing between the insulation and the entry to the ferrule, otherwise again stress on the copper from the insulation is likely.

David Stone said:

As the only terminal connection is to a single piece of copper (the ferrule) I cannot see how anyone could claim this is somehow TWO, conductors!

I think I agree with your basic idea here - but I think it depends what you decide the conductor we are talking about is. If we are saying that terminals are for termination of conductors of wiring, then clearly we have two conductors (of wiring).

Once the termination is made, for example, the conductor of the wiring and the conductive parts of the terminal, and whatever conductive parts continue on the other side of that terminal, are clearly now only a single conductor, which illustrates the fact we must be talking about different conductors to start with.

So, yes, what goes into that side of the terminal, with a twin ferrule, is a single conductor, but the ferrule clearly has two conductors entering it. The ferrule is not a connector, and hence when made off, there are clearly two conductors going into the terminal.

But that doesn't make you wrong, it makes the situation difficult to interpret.

Sadly, the IEV definitions of terminal and conductor don't help.

I think we might be getting to the point of asking whether the standard in question is ambiguous in this respect?

Dave in the shed said:

I think that it's rather a shame that the standards organisations don't publish (as far as I know) official clarification documentation after the publication of a standard which is (perhaps inevitably) found to be ambiguous, unclear or otherwise in need of clarification.

Have a look in BS 0 - that situation would be an Amendment to the standard.

If we feel strongly about that, we can submit a comment to the relevant committee. It's more likely to have something done about it, if you suggest some alternative wording ... or perhaps in this case, two alternative suggestions for the wording, one if the interpretation is only a single wire to the terminal, another if two (or more, with appropriate conductor preparation products) are used.

GTB said:

I dont think you will get a definitive clarification etc. It is like thousands of other regs and standard items where it is down to one's interpretation.

Agreed. Although we can submit a comment or query, with suggested changes (see post in response below).

gkenyon said:

So, you can immediately see the problem,

After posting, I had the thought whether you'd ask if I'd ever seen any real-world issues with this?

Well, the answer is yes ... which is why I've looked into the ferrule sizes and copper+insulation diameter and have the data to hand readily.

A similar problem arises with wire constructions of larger than standard insulation thickness, such  as some hot condition rubber types.  Then we end up core stuffing  with extra strands to fill out to the size of a crimp terminal that suits the insulation diameter,

In reverse there are XPLE railway cables and PTFE aerospace cables with considerable thinner insulation for a given voltage than the PVC equivalent, and then the wire tends to fatigue break where the strands enter the tube, and the use of RTV as an anti-vibration snotted into the cup like an ice cream  is called up in the worst vibration cases. (helicopters or tanks ).  Basically the old needs to be  'suitable for the application' comes back to bite us.

Mike,

Thanks for your input gkenyon,

Now the debate seems to be getting really interesting. I'm guessing from your words that you might know a thing or two about the mechanism of getting amendments made to standards, and also that you suspect that what we're discussing here might just be worthy of such an amendment.

It does appear from all the replies here that everybody who has contributed does indeed support the idea of using dual ferrules. Also nobody has expressed an opinion that the standard is already crystal clear in respect of the ferrule issue. It therefore appears to me that a submission for amendment might just be a good plan. This isn't something I've been involved with before. Are you able to assist in any way in doing this?

After careful consideration, I think that I do feel reasonably strongly about this. If a machine builder or panel builder were to make extensive use (or perhaps even modest use) of dual ferrules in a well-engineered, safe and robust  manner and was obliged to do so because of space constraints, only to have an end-user reject the work because of their internal policies relating to their interpretation of 60402; there could be a considerable cost implication for the builder in undertaking the appropriate remedial work. In some extreme cases I could conceive that rework of such a machine might be impossible without resorting to larger cabinets due to lack of DIN rail space.

Dave (not in the shed today).

Please connect and send me a private message. I can provide some guidance for you.

Glad you're not in the shed, it would be rather warm!