The absurdity of the Electricians trade

Discussion in 'Electricians' Talk' started by unphased, Oct 13, 2018.

  1. Risteard

    Risteard Screwfix Select

    LOL. Another one pretending to have me on their ignore list...
     
  2. Coloumb

    Coloumb Screwfix Select

    Lee, this is a case in point. You won't put forward an argument because you know I'm right. So you resort to contradiction. So if you don't like it why stay on the forum? I just don't get it.
     
  3. Coloumb

    Coloumb Screwfix Select

    It's more or less impossible to ignore any members on here. I soon realized this. The ignore function doesn't really serve any useful purpose.
     
  4. Risteard

    Risteard Screwfix Select

    Well that's definitely not true...
     
  5. Magicspark

    Magicspark Active Member

    Keep arguing with yourself...go on! We are laughing at you!
     
    Risteard likes this.
  6. Richard_

    Richard_ Screwfix Select

    Crikey, we haven't even mentioned equipotential or earthing back boxes yet....
     
  7. Sparkielev

    Sparkielev Screwfix Select

    Whatever you do don't mention 3metre rule and switch fuse
     
  8. Coloumb

    Coloumb Screwfix Select

    :) oooo my favorite.
     
  9. Richard_

    Richard_ Screwfix Select

    Ring v radial?
     
  10. Bob Rathbone

    Bob Rathbone Screwfix Select

    Then that will be covered by the Electricity Supply Regulations, but are they a statutory document? I doubt it. But as you say, the supplier does have the right to refuse a supply in extreme cases. During privatisation this right was revoked, but about 4 years ago it was re instated.
     
  11. spinlondon

    spinlondon Screwfix Select

    ESQCR is Statutory.
     
  12. Coloumb

    Coloumb Screwfix Select

    I don't think so Bob, it would take an act of Parliament to repeal the act and then another to put it back.
     
  13. Coloumb

    Coloumb Screwfix Select

    @spinlondon I'm going to give this one last try or we will just have to agree to disagree.

    Firstly, here is a typical set up as given by uk power networks...

    https://www.ukpowernetworks.co.uk/internet/en/help-and-advice/documents/A typical domestic power supply.pdf

    Part 8 says this about the tails from the meter to the cu...

    8. Consumer Unit Tails These cables connect the consumer unit to your meter. They can be connected and maintained by your electrician because they’re part of the internal wiring.

    ie they are nothing to do with uk power networks or the rec. They belong to the consumer, form part of the internal wiring and are therefore must, by definition, come under the remit of 7671.

    Ok so...

    1. Consider a brand new connection for a new build. The rec has been in an installed a cut out, a meter and a isolater. The isolater hasn't had had it's "feed" end tagged so you can access the terminals. It's been left energized and your on your own. You have been commissioned to install the electrics in the house so you put in a cu, regular ctt's etc and proceed to connect the cu to the isolator.

    So according to your argument, for this to meet the requirement of 7671 and the ESQCR, you must ignore the fact that there is a fuse in the cut-out as you don't have anyone's permission to use it.

    So according to 7671, the only option, the absolute bottom line, is that...

    Sizing and the method of installation of these cables must be agreed with the distributor (which you can't do).

    If Regulations 434.3(iv) and 433.3.1(iii) are not met (they are not) then overcurrent protection, complying with Regulation 434.2.1, should* be installed close to the origin.


    You don't have permission fro the rec/supplier and no one's there to ask.

    So your only option is to comply with 434.2.1 which says...

    434.2.1 Except where Regulation 434.2.2 or 434.3 applies, a device for protection against fault current may be installed other than as specified in
    Regulation 434.2, under the following conditions:

    In the part of the conductor between the point of reduction of cross-sectional area or other change and the position of the protective device there
    shall be no branch circuits or socket-outlets and that part of the conductor shall:

    (i) not exceed 3 m in length, and
    (ii) be installed in such a manner as to reduce the risk of fault to a minimum, and
    NOTE : This condition may be obtained, for example, by reinforcing the protection of the wiring against external influences.
    (iii) be installed in such a manner as to reduce to a minimum the risk of fire or danger to persons.


    So, in this case, according to what your saying and this is your argument, the total bottom line is that you have to install a switch fuse, keep the feed from the s/f to cu less than 3m, route the tails to keep fault risks to a minimum, find a way to reinforce the protection of the wiring against external influences and keep the fire risk down. I presume all of this means (when I check the guidance on 7671) that the tails have to installed in some sort of type tested metal enclosure that meets the minimum requirements of some sort of BS.

    So is that what you would do in this situation? Please, can you just give an honest answer, I'm not trying to find a way to make you look stupid, I'm not like magicspark etc, I'm just 100% genuinely interested to know what you would do.


    *note the word should, not must.
     
  14. spinlondon

    spinlondon Screwfix Select

    You’re getting there.
    If the DNO have installed an isolator for the consumer to connect to, then that is the origin of the installation.
    Normally the origin is at the meter.
    Insulated and sheathed tails meet the requirements for double insulation and the sheath is considered as being mechanical protection.
    As such further mechanical protection is not required, however, if it is provided, it doesn’t have to be by means of a type tested enclosure as that particular requirement applies to CUs or similar.

    Apart from that, you do seem to have the gist of it.
     
  15. Coloumb

    Coloumb Screwfix Select

    But you would still have to install s/f from the isolator (or origin) to the cu in order to overcome the requirements of 434.2.1 otherwise you need to comply with items i, ii, and iii. It's not enough to leave the tails unprotected from the isolator to the CU if you accept they have no fault/overload protection. The choice is a) install a s/f or b) follow options i, ii, and iii.

    So I don't really get your argument. Surely the only option is to follow 7671 to the letter as you don't have permission, not to just go ahead and put your tails in, leaving them unprotected.
     
  16. spinlondon

    spinlondon Screwfix Select

    The purpose of installing a S/F is to comply with (i).
    If the tails are less than 3m, a S/F is not required.
    There does seem to be an erroneous belief that an isolator will trip at it’s current rating.
    Another one, is that an RCD will do the job of a S/F.

    The sheath on tails is to comply with (ii).
    The sheath reinforces the basic insulation effectively making the tails double insulated.
    Hence they are used to provide earth fault protection in TT installations.

    (iii) is a little more subjective.
    Placing the tails out of reach, up high above the front door, under the stairs, in the cellar or just boxing everything in, in a cupboard will minimise risk.
    The cupboard would not have to be type tested or constructed from non-combustible material if the CU is itself type tested and constructed from non-combustible material.
    In many instances the CU is on the other side of a wall to the meter, so the building itself provides protection.
    In some instances trunking or conduit may have to be used.
     
  17. Coloumb

    Coloumb Screwfix Select

    The regulation says

    434.2.1 Except where Regulation 434.2.2 or 434.3 applies, a device for protection against fault current may be installed other than as specified in
    Regulation 434.2, under the following conditions:


    In the part of the conductor between the point of reduction of cross-sectional area or other change and the position of the protective device there
    shall be no branch circuits or socket-outlets and that part of the conductor shall:


    So, in our case, 434.2.2 doesn't apply as we are ignoring the fuse in the cut out.
    434.3 doesn't apply as we are not applying part (iv) as we don't have permission from the supplier to use their fuse.

    So our ONLY option is to follow the reg 434.2, which set out three conditions, all off which need to be satisfied in order to reach compliance ie, i, ii, and iii.

    Therefore, we are not using any kind of fault/overload protection so we have no choice but to follow i, ii, and iii. None of them are optional, it's all of them.

    So they idea of fitting a switch fuse is totally irrelevant as it's not an option. If you choose to fit a switch fuse then you can happily ignore 434.2.1 and make the tails as long as the Zs of the fuse will allow etc as the general requirements of the regs will apply. Fitting one of the same rating would be pointless as both the cut out and the s/f would pop at the same time. Fitting one of half the rating of the cut-out fuse would ensure discrimination. If a 60a cut out is supplied then a 30a s/f would be required, which wouldn't really last long in a domestic.

    I would doubt this very much. Under the general requirements of 7671 insulated and sheathed cables are considered fine, this is an exceptional case, and our attention is drawn to this in the wording. It is clear we must somehow exceed the general standards. There is even a note to go with it telling us this.

    In the GN6, fault and over current protection, it gives a list of items that must be specified in order to satisfy items i, ii, and iii. Among them are such things as requirements for type tested assemblies that the manufacture needs to specify, how to transport the assemblies and a list of maintain ace requirements. I would not think anything on your list would approach any where near these requirements.

    The regulation 434.2.1 is meant for bus-bar assemblies, where the taps from the main busbar must be i) less than 3m, ii) made from say, solid copper bars and iii) enclosed in steel. You are also allowed to reduce the csa, as per this bit.

    In the part of the conductor between the point of reduction of cross-sectional area or other change and the position of the protective device there
    shall be no branch circuits or socket-outlets and that part of the conductor shall: etc.






     
  18. spinlondon

    spinlondon Screwfix Select

    I don’t know what to say?
    You are clearly ignoring the evidence of your own eyes, the information contained in BS7671 and clearly misinterpreting some parts of BS7671.

    You need to break it down, stop trying to deal with multiple points in a single post, keep it simple.

    For instance with Regulation 434.2.1 which you believe only relates to bus bars.
    How many bus bars have you come across that have branch circuits and socket-outlets connected to them?
     
    Last edited: Oct 18, 2018
    Magicspark likes this.
  19. Coloumb

    Coloumb Screwfix Select

    Well do you think that the reg 434.2.1 relates to the tails between the isolator and the CU? Specially, do you think the three items in the reg give you the requirements you need meet to install the tails?
     
  20. spinlondon

    spinlondon Screwfix Select

    Let’s get something straight.
    Regulation 434.2.1 relates to all conductors, I don’t think this, I know it.
    It relates to tails, bus bars, T&E, SWA, flex, etc.
    Another thing that needs getting straight, is that tails are not exceptional.
    They are just conductors, that’s it.

    To comply with regulation 434.2.1 with regards to tails:
    (i) Ensure the length of conductor is less than 3m.
    (ii) Ensure the conductor is sheathed.
    (iii) Ensure the conductor is out of the way of harm or provided with extra protection, such as conduit or trunking.
     

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