EN60204 and twin ferrules

Graham,

Nice bit of relevant data - many thanks. WD2.5's are generally my terminal of choice so doubly nice.

Graham,

There is a similar but not quite identical staement in 60079-14 for protection method "e" conductor terminations.

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Now given the fundemental principles of what Exe is and how it achieves safety in a potentially explosive atmosphere, then maybe similar thought for termination of conductors for machinery?  After all are we not trying to achieve a robust and mechanically and electrically sound connection.

GTB

I followed this thread with interest, to see how it developed.

When I first looked at it, I already knew the answer for, at least, Wedimuller DIN terminals - those terminals are, in their data sheet, stated as capable of accepting 2 conductors ... and twin ferrules.

For example, look at the data sheet for the WD 2.5 terminal often seen in control panels. It is specifically stated that 2 clampable conductors with equal cross-section of either 0.5 sq mm or 1.5 sq mm may be terminated.

So, in this case, if ferrules are specified (or used - it is, I would have said, de-rigueur for control panels with stranded conductors), a twin ferrule is the only option. But twin-wire ferrules are also specifically stated as acceptable.

So, for these particular terminals, if anyone raises the question, just fire the data sheet straight back at the client's engineer or witness test attendee.

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!

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).

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,

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.

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).

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.

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?