3rd Amendment Tails Entry

Discussion in 'Electricians' Talk' started by DanielQ, Oct 8, 2018.

  1. unphased

    unphased Screwfix Select

    Just want to gauge some views on the AMD3 CU's.
    My view is you don't need to have fire rated glands, metal glands or fire rated inserts or metal inserts in the metal cased CU. It was never intended that the metal CU was to RETAIN a fire, only that the CU was made from non-combustible material. I know that manufacturers and many electrical journalists went overboard with the CU requirements and as a result a lot of things were arried out to the AMD3 CU that were unnecessary and were all interpreted differently. It is my view that you can quite legitimately use standard rubber grommets in 20mm and 25mm holes drilled in the CU. The lid/facia does NOT need to be top hinged, tails need to be firmly secure in the entry point through ONE hole. Some of the grommets being offered for sale such as the TKS 32mm glands would not provide sufficient support for the tails like the Wiska TKS32 whereas the compression style glands do provide support. Non-combustible was the wording used in the Regulations not fireproof, they are two completely different requirements and the smart alecs who think they do mean the same thing are wrong. I spent years in the fire protection measures field and I know the difference.
  2. Comlec

    Comlec Well-Known Member

    @unphased have a peek at this

    From Wilex, suggests cable entry must maintain IP rating rather than fireproofing.
  3. seneca

    seneca Screwfix Select

    I agree with most of that UP with one exception, I think that clamping type glands for the tails are only necessary on TT supplies, TN supplies can use normal grommets.
    retiredsparks likes this.
  4. spinlondon

    spinlondon Well-Known Member

    It’s not been put into the Regs.
    What has been put into the Resgs, is that all conductors of a circuit must be within the same ferrous-magnetic enclosure.
    Last edited: Oct 10, 2018
  5. spinlondon

    spinlondon Well-Known Member


    Do you think we used plastic glands for these 185mm2 concentric singles on this 33kV transformer?
  6. Coloumb

    Coloumb Well-Known Member

    So what if the tails happen to be two core SWA and an extra parallel earth is installed? Your happy to take a pop at me for not being a spark but take a look in your own back yard before you start quoting the regs incorrectly.
  7. Risteard

    Risteard Well-Known Member

    SWA is not appropriate for meter tails. It might be used for a distribution circuit. SWA has a special exemption from this Regulation (and has only had this exemption for a few years - before that it was prohibited to do this with a separate cpc). So stop shooting your mouth off - you're still full of ****.
    Magicspark likes this.
  8. Coloumb

    Coloumb Well-Known Member

    Lol - what reg?
  9. spinlondon

    spinlondon Well-Known Member

    No specific Reg. but the tails, as with any other conductor, require fault protection which SWA would not provide.
    A few years = 10.
  10. Coloumb

    Coloumb Well-Known Member

    SWA is perfectly usable for tails. You could use two core and run in a paralleled earth. In fact, as a design, it would be better than PVC tails and could be used with a PME earth.
    Last edited: Oct 10, 2018
  11. spinlondon

    spinlondon Well-Known Member

    Fault protection?
  12. Coloumb

    Coloumb Well-Known Member

    ? what fault protection
  13. spinlondon

    spinlondon Well-Known Member

    As in, where is the fault protection, or what method of fault protection is being provided?
    Also where do you make off the gland?
  14. Coloumb

    Coloumb Well-Known Member

    The cut-out and use and some sort of adaptable box made of non-ferrous material.

    I don't really understand the point your trying to make.
  15. spinlondon

    spinlondon Well-Known Member

    Ok, so you have permission from the distributor to use their cut out to protect the tails then?
    I suppose, you’ll butt up the adaptable box against the meter so there will be no exposed single cores?
    Will the distributor be happy with that?
    Which end of the SWA will you be earthing again?
  16. Coloumb

    Coloumb Well-Known Member

    Why would you do that? You would run the tails to an adaptable box then gland off you swa from that. You could then run 3 core to your CU or use 2 core if you steel meets the required CSA or use 2 core with an paralleled earth sized correctly. Then make sure your Zs is within the cut out fuse tolerance. If you used method 3 it would be impossible to run the earth through the same hole in the CU wouldn't it?

    Ergo sum, it's rubbish to say the earth has to go through the same hole in a ferrous CU as the tails. Or SWA can't be used for tails.
    Last edited: Oct 10, 2018
  17. spinlondon

    spinlondon Well-Known Member

    Does this mean you agree SWA is not suitable for tails?
    Might be rubbish, might not be.
    It is however a requirement of BS7671.
  18. Magicspark

    Magicspark Active Member

    My understanding is that the term “tails” is the non technical term, often used, referring to single insulated and sheathed cables that connect the meter to the consumer unit, distribution board, switch fuse or similar. I have never heard a practicing electrician refer to SWA as tails.
  19. Coloumb

    Coloumb Well-Known Member

    Meter tails are not defined under 7671. A meter tail comes out of meter and goes into a CU afaic. Clearly it IS NOT a requirement that a cpc HAS to go through the same hole as the phase and neutral.

    I suggest you re-read what I have posted.
  20. spinlondon

    spinlondon Well-Known Member

    Not aware that anyone said tails are defined under 7671?
    We all know what tails are, though they don’t necessarily have to go to a CU.
    In fact you’ve just proposed that they go to an adaptable box.

    I don’t see any point in re-reading what have posted.
    You first posted that SWA was suitable for tails, then you posted that you would run tails to an adaptable box and then run SWA (I presume to the CU).
    You also posted some guff about 3c and 2c and the steel meeting the required CSA (required for what?), there was something about Zs being within cut out fuse tolerance?

    What is this big thing you have about the earth conductor going through the same hole as the other conductors, anyway?

    You still haven’t mentioned where the fault protection is going to be.

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