EN60204 and twin ferrules

No-one has answered yet, so I thought I would chip in. How many connections are in the terminal using twin ferrules? One.

Is the terminal designed for one connection? Yes.

What is the difference between using a twin ferrules and joining three conductors within an enclosure and then putting the (possibly bigger) conductor into the terminal?

Hi OlympusMons - thanks for your input.

The point you're making is exactly in line with my thinking. My belief is that it is indeed acceptable within the scope of 60204 to use twin ferrules on the basis that a ferrule with two wires is considered as a single conductor. However, I have discovered a couple of fairly straight-talking parties online (who appear to be fairly professional and knowledgable) who categorically state that twin ferrules are not allowed because of the two conductors one terminal rule.This is what sent me off on my hunt for definitive guidance.

Any other wisdon out there?

Only thing I can add is, a twin ferrule is designed for 3 terminations, two in, one out.

I think the design of the terminal is what is relevant, and what type of cable it accepts, eg  solid, stranded, fine wire, and whether it is designed to accept two of the above. 

An MCB cage clamp is designed to accept two ring circuit conductors for example, and at a push a spur fed from it too.

Do you mean this sort of thing? https://uk.rs-online.com/web/p/bootlace-ferrules/1788734?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_Connectors_Whoop-_-Bootlace+Ferrules_Whoop-_-1788734&matchtype=&pla-302478546419&cq_src=google_ads&cq_cmp=9771206614&cq_term=&cq_plac=&cq_net=g&cq_plt=gp&gclid=EAIaIQobChMIjaXf7ej2-AIVCdPtCh2F2APSEAQYBSABEgL4HfD_BwE&gclsrc=aw.ds

I'd regard that as one conductor.

I agree absolutely.

I'm a bit of a purist when it comes to doing things correctly (like ensuring that the correct type of wire is used in a ferrule). Sometimes that purist approach is driven simply because it is right and proper from an engineering point of view (including of course from a safety perspective) and sometimes it's driven by a need to conform to the requirements of a standard or directive for compliance reasons.

My current dilemma is that I'd like to declare compliance with 60204 on a machine I'm currently designing/building but I'd also like to use twin ferrules in some locations due to space constraints. To add to the fun, the end client is pretty strict on compliance-related issues so I'd really like to have some definitive guidance in place before the finished machine gets condemned by an over-zealous client.

Still hoping for more wisdom..... anybody?

Hi Chris Pearson - thanks for your input.

That type of ferrule is exctly what I'm referring to. It's encouraging to hear your "one conductor" view. Do you know of any published guidance or other definitive info which supports your view? I'd really like to track down something a bit more solid so that I can effectively counter the views of the nay-sayers.

Well the key is "where the terminal is designed for that purpose." I can imagine an unlikely but possible  situation where one terminal is so close to its neighbours that a large funneled bootlace ferrule does not fit, but apart from that, if the terminal can accept ferrules, then if the strands in the tube come from more than one wire, or not, is not important- it is the ferrule that is sized  to do that.

So are your terminals suited to ferrules at all, and if so is there enough room to fit a dual entry one without collisions? In your place I might drop an email to the makers of the terminals you have in mind checking that ferrules of that style are OK.

Mike.

Thanks for your input mapj1. Glad to hear that you're also of the same general view about this.

It seems that the general opinion amongst those who know a bit about electrical engineering is the common sense opinion that the use of a dual ferrule is just as valid as a single ferrule (subject to the usual caveats about suitability of the terminal, wire type and so forth).

In addition to all this wisdom I'm still keen to do some more digging to find anything more definitive (in the context of the interpretation of the standard).

Any more knowledge out there?

Afternoon,

My understanding and interpretation over the years and as many have indicated below. The terminal design is what is important. So if a terminal is only designed for one "Conductor" then thats because the clamping mechanism has been designed to tighten and possibly lock around one single cylindrical shape in other words the pin of a cable lug or bootlace ferrule.

The wording is indicating if you had two solid conductors or indeed two pins of cable crimps or two bootlace ferrules the manufacturer cannot then guarantee with the standard that those conductors will not come loose. Whearas what I call a "Piggy Back" terminal has basically a rear and front layer so two conductors, one in each layer and hence design of terminal makes everything common.

As long as the conductor size and type and Max loads are appropriate for a twin ferrule, are prepared and inserted correctly and crimped down with the appropriate ratchet crimping tool then nothing wrong with that.

I have had a few clients that in their specs, reject twin ferrules, simply due to trying to work on a single conductor in the future. Also if the idea of the twin ferrules is to loop lots of terminals together so to form a common terminal rail I would reject that and use the terminal manufacturers own designed linking assemblies/components for doing that.

In fact if you think about it, its acceptable where using a honeycombe linking assembly that a single conductor goes in with one of the points of the honeycombe rail to make it common, but in some ways that situation is two conductors in a terminal!

Cheers GTB

Thank you GTB - valued input once again.

I'm in agreement with everything that you've said - all pointing towards there being nothing forbidden in the use of the humble twin ferrule.

I'm unfamiliar with the terminology of "honeycomb linking assembly" but I'm guessing that you might be referring to something like this:

If that is indeed what you're referring to then it's an excellent relevant example that I hadn't thought of. The MCB commoning bar shares a lot of commonality with the concept of the twin ferrule in terms of the 60204 one conductor/two conductor quandary - marvellous stuff.

Thanks again.