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Multicore cables (YY but not PVC/PVC)

jbrameld
I wonder if I could previal for some learned opinions.


We undertake installations of stage lighting amongst other things, and often use a 19-core 'YY' type cable (though it isn't really YY as the insualtion and sheathing is not PVC/PVC - it is a LSF variant) for links between switched power units or dimmers and internally wired lighting bars.


We have undertaken many such installations, and we are registered with the NICEIC who have audited and inspeced many such installations and passed them.  We have also raised specific questions with them on the use of the cable and we get varying answers.  They are never willing to give an emphatic 'yes', but neither do they say 'no'.


As I understand it - there is not a relevant construction standard that covers this type of cable construction, so it can't comply with a standard that doesn't exist.  There are however many standards (many of which form normative references for construction standards of other cable types) with which it does conform.  These include EN 50525-1 (General requirements) EN 60228 (conductors) and various fire performance standards (EN 50575, EN 60754, EN 60134 and EN 60332).  We also know that the insualtion and sheathing material is standards-compliant and is commonly used in cable manufature.


We are embroiled in a dispute with a main contractor who is claiming the installation is non-compliant as the cable does not meet a construction standard. Reg 511.2 allows for use of euipment not covered by a Britsh or Harmonised standard if the designer/specifier confirms that the equipment provides at least the same degree of safety.  This cable is covered by multiple standards but not a single 'construction' standard that is applicable to this type


We have undertaken what we believe to be a thorough assessment of this cable which is attached here:  Assessment of Cable NILTOX LF 319.docx


The use of the cable is noted on the certificate and the assessment and supporting documentation from the supplier is attached, but the main contractor is still refusing to accept this route.


So a couple of questions for the learned community:
  1. Have we missed anything in our assessment, or does it seem thorough and complete?

  • Should the use of this cable be recorded as a 'departure' (our agument is that we have complied with 511.2 and therefore it is not a departure) or just recorded as a note?


Thanks in advance.  Happy to answer any further questions.


Jason.
  • 0
    OM

    What do you think the contractor should use then? You need a multicore (unless that was not required but they often are) 18 way LSZH flexible cable. I have often had special cables made, and the datasheet says made to the general requirements of BS6500 or EN  whatever. Many manufacturers offer this, are you trying to say these are not permitted either, because this is typical "level playing field" C*** of the kind we used to endlessly get from the EU. We call it yy, as an unscreened multicore cable but the insulation and sheath is of another approved type, I cannot see that this makes it in any way not permitted and the lack of a standard as Graham says cannot disallow YY as these are widely used all across Europe! Perhaps this is "do as we regulate" while we do something else? BS7671 says we should use items to appropriate standards but if there is not one other things can be used as long as they are no less safe. This cable is obviously no less safe than any PVC one, it has a higher working temperature and better insulation, a tougher sheath and the same conductors. What more could one want?
  • 0
    David - answers as follws:


    The cables are terminated to a terminal box on an internally wired lighting bar at one end, and to the bypass dimmer at the other end, so basically from dimmer/switch pack to fixtures.


    They are in trunking at the dimmer room end, flexible conduit at the IWB end and on basket above a false ceiling in between.


    He would be satisfied with any BASEC approved cable or cable to a British or Harmonised constructon standard.  We could use T&E, or a multicore SWA, or 'socapex' cable (to a Harmonised standard) or multiple 3-core flexes - not that I am suggesting that all of these would be a 'good' solution but they would satisfy this individual.  The use of this cable was convenient to us as it is easy to install. The IWB is on fairly long stud drops so may be subject to slight movement.


    I'm not certain there is a direct clause relating to LSZH but it would fall under the general requirement for cables to meet the Constructon Products Directive (which it does).


    Graham - I'll check out the info in the OSG, but our approach was to provide an equivalent assessment as-per 133.1.3.


    Olympus - thanks for the info on the typo.


    Jason.


  • 0
    Graham, consider this, this, a yy cable is exactly the same as any other fleible PVC cable with a standard except it has more cores, may be available in a different set of core sizes and number of cores. This is a fault with the standards not the cable, they need to be generic not isolationist. An example, I am manufacturing something which needs a variation on a metric thread say 0.2175mm pitch. Can I not use this in a product because it is not "standard"? I can, the standard allows variations based on requirements but sticks to a standard thread form. Generic, with "preferred" sizes. PG threads were always a German speciality "Panzer Gauge", still widely used on German electrical bits. I am sure it has a copied EN spec, but not a BS (the BSI search find nothing).
  • 0
    jbrameld:

    David - answers as follws:



    Graham - I'll check out the info in the OSG, but our approach was to provide an equivalent assessment as-per 133.1.3.



    Jason.


     


    Effectively, OM is correct - it is a departure, and you are effectively following that, See also Section 511 of BS 7671. The OSG just goes the extra mile and provides further guidance on what would be considered acceptable in this case ...


  • 0
    Dave, not saying anything is wrong with the cable. And nothing is wrong with filling in the departures box on the EIC (133.1.3 also mentioned on the departures box on MWEIC), and providing documentation/assessments etc. But it looks like a departure and as such doesn't fulfil the contract, as far as we know.
  • 0
    davezawadi (David Stone):

    Graham, consider this, this, a yy cable is exactly the same as any other fleible PVC cable with a standard except it has more cores, may be available in a different set of core sizes and number of cores. This is a fault with the standards not the cable, they need to be generic not isolationist. An example, I am manufacturing something which needs a variation on a metric thread say 0.2175mm pitch. Can I not use this in a product because it is not "standard"? I can, the standard allows variations based on requirements but sticks to a standard thread form. Generic, with "preferred" sizes. PG threads were always a German speciality "Panzer Gauge", still widely used on German electrical bits. I am sure it has a copied EN spec, but not a BS (the BSI search find nothing).


    OK, but at the moment we just need to work with the fact that there isn't a standard for this ... but the default position in BS 7671 is that all equipment (which encompasses cables) complies with an appropriate standard. There is a mechanism to use non-standard products, and the guidance in this case has been provided.


    In terms of your product, if you MUST have a variation on a standard thread for some very good technical reason, then yes I'd agree go for it ... but what's the point of having standard threads if at the drop of a hat and for no good reason, someone decides on using an odd-ball variation? Especially pertinent as it seems there's some common-sense discussions going on at the moment to do away with in-built obsolescence and the explosion of proprietary variation (which of course, is endemic in brand-protectionist drivers and interfaces etc. even outside the physical layers of products these days).


    What we are talking about here, however, is not really aligned with the pitch of thread (i.e. not just about the copper conductors and insulation thickness). It's perhaps more equivalent the strength tests and material makeup of the fixings that use those threads, perhaps mechanical and environmental performance requirements and tests for the whole assembly that is the cable ...


  • 0
    Thanks Jason. I was hoping you had some connectors somewhere as it is common for theatre type installations to use flexibles and cables so that everythig may be move around to suit production circumstances. Having both ends hard terminated is going to be a problem in use, but that is down to the designer. As you need a LSZH cable I suppose singles in trunking would be the obvious construction given the limitations, but much more difficult to install and impossible to change easily.

    Was there no design approval stage involved with the main contractor, you sub-contracted everything, including design, installation and test/commissioning? In this case I think he would find it difficult to say that the design you have offered is unsatisfactory, unless the contract specifically says that everything used must be to a British or possibly EN standard. The exact words from BS7671 are in regulation 133.5, and I believe you meet these, although the test documentation in part 6 should note the new material and point out that it is as safe than any other materials you may have used, for example singles in trunking, and it is better able to deal with possible temperature rise when spread across cable tray, and is suited to the drop bar connections.


    My understanding is that you have not deviated from BS7671, except perhaps in the EIC where the new cable type should be noted. It is the weasel words in the contract which could cause trouble.


    Kind regards

    David CEng etc
  • 0
    Dave,


    For context this is a run between a dimmer in a control room and fixed IWBs in a school hall - they will never be moved about or re-congifured - it's not a 'real' theatre! (we do plenty of those too)  It's highly unikley with risk assessments and regulations, and associated perceived fears of 'rules say no' in schools these days that anyone would regularly go up and even re-focus the lights let alone move them or rig something else on the bars!  We'll most likely be the next people up there come inspection time unless something goes wrong in the meantime.


    There are some weasely words around standards in a clause in the contract, but our documentation lists multiple British Standards with which the cable does comply, so it can't be said that the cable does not comply with Standards.  As you say, it is a fault (gap) in the Construction standartds for cables that this type is not covered.


    There is a note on the certificate relatiing to the use of the cable.


    No design approval with the Main Contractor - they leave it to us as specialists - but our quotation did specifiy the cable type that we use and they did accept that.


    Jason.
  • 0
    Is there a national (e.g. German) construction standard for YY (etc) cables? I keep seeing VDE 7030 mentioned on data sheets (but haven't been able to discover its status).

      - Andy.
  • 0
    In most cases I agree with you Graham. The problem is with new products, where standards are always behind the availability, except as with AFDDs for example, they existed elsewhere but not in Europe and a standard was a way to introduce them to a market.


    The cable above is covered by all the generic standards as Jason described, but not a product standard. In most cases product standards reduce the availability of alternatives, but this was always the idea, particularly in Europe, because it also reduces competition substantially, the "level playing field". Perhaps BS7671 should be altered to say that a new product without a standard, but designed to match all the generic standards applicable is fully acceptable. I can see no reason why it should not be, and BS7671 appears to accept this position as discussed above. It would be very difficult to argue that this cable is in any way worse than say a 3 core version of the same with LSZH (XLPE or similar) which meets the same generic standards.


    Kind regards

    David

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