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Discuss Consumer Unit Installation Up to Scratch??? NICEIC approved Installer. in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Hi. I'm newly qualified as a domestic installer so well aware I've got a lot to learn about the real world but...

    I looked over a friends consumer unit today. It was recently installed by a NICEIC approved spark. I noticed lots that didn't seem right to me, and I'd appreciate some feedback on which bits are actually bad and which are just "how it really works on site".

    1) There's no main bonding in place to either the gas or water. The certificate has all the relevant boxes ticked to say it IS there and complies with regs.

    2) The tails haven't been increased to 25mm and they don't all enter through the same knockout.

    3)The main earth comes through a large gland leaving plenty of room to poke a finger through.

    4) It's been RECORDED on the certificate as a TN-C-S, and does superficially look like one (it's one big cutout). I'm convinced it's a TN-S. It 100 year old house. There's actually a bit of lead sheath visible near where the cable enters the house and there is continuity between this and the MET.

    5) "N/A" is recorded in the Ze box. Maybe related to the confusion between TNS and TNC-S?

    6) All of the Zs are recorded as 0.35 ohms. This seems conveniently the same as the TN-C-S Ze requirement of 0.35 ohms so I checked it. Got 0.61 upstairs, 0.48 downstairs and a Ze of 0.19 at the board.

    7) The main fuse is still 60amp. The max demand on the cert is recorded conveniently as 60amp.

    8) Inside the consumer unit, three 2.5mm neutrals have been joined by wago all in to one 2.5mm neutral and extended to reach the terminal bar. This has also happened with a 4mm neutral to a 2.5mm. Surely this has de-rated the cable?

    Many thanks for reaching the end of my long post!
     
  2. Pete999
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    Pete999 Trusted Advisor

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    Location:
    Northampton
    Some pictures would be nice shinypen
     
  3. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Haven't got one I'm afraid. Didn't think to take one. I'll get them to send me a pic of the cutout. They'll be too frightened to take one of the inside of the consumer unit! Essentially, the 3 neutrals belong to the central heating and they've been joined together and extended the final 10cm by one 2.5mm neutral. Thanks.
     
  4. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    need a pic of the CU with the cover off before making comment.
     
  5. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
  6. Pete999
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    Pete999 Trusted Advisor

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    Location:
    Northampton
    How long ago did they have this work done?
    Did they get a certificate?
    If it's a recent job, and the customer is unhappy with the work, you said the Electrician was an NICEIC Electrician, then they might be best advised to contact them and complain. :(
     
  7. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Only couple of months ago. Have certificate which is where I got all his info from. You can see outer sheath on cable and a bs951 (maybe) label attached to.

    Just wondered what the consensus was before I advised them.
     
  8. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    that TN-S clamp is non-standard and there's nowt connected to it, so TNC-S. as per the block on side of cut-out. always assuming that it's connected.
     
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  9. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Yep. There was continuity between that label and the earth block.

    Getting the type wrong not the end of the world maybe? But why no Ze recorded. Surely this compulsory?
     
  10. mache
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    mache DIY

    Looks to me like there is a cable of sort emerging behind the clamp in the shadows.
     
  11. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    There do appear to be areas of concern but I agree it seems to be TN-C-S. Try and get a pic of the CU.
     
  12. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Yes there is but it doesn't go to either the gas or water and really be attached there anyway?
     
  13. Pete999
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    Pete999 Trusted Advisor

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    Location:
    Northampton
    Yes I agree try and arrange to get a pic of the innards of the CU, I'm sure if you explain to the customer they would be willing, I certainly would if I was in their shoes.
     
  14. Pete999
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    Pete999 Trusted Advisor

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    Location:
    Northampton
    Off topic, Tel how are the dogs doing?
     
  15. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Is there evidence of bonds within the CU.
     
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  16. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Sorry got myself a bit confused there. To clarfy, my theory is it's a TNS and the label is attached to the lead sheath then has an earth running up to the earth block and then it definitely goes from there to the C/U.

    Do TNC-S ever have exposed lead outer sheaths and if so would there be continuity between that outer sheath and the MET?
     
  17. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    No evidence no. I've asked them to send a pic of the internal but they're not up for it. Thanks everyone.
     
  18. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Looks like an old TN-S supply converted to TN-C-S. Where does the green/yellow from the earth block go to.
     
  19. PEG
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    PEG Trusted Advisor

    Location:
    Manchester
    Without having a poke around,always difficult to give practical opinions...

    The one definitive thing i can assure you,is placing the word "approved",at the end of anything,means squat ;)
     
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  20. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Oh I see now.
    Oh I see now. Thanks. The green/yellow from the earth block goes to the c/u earth met.
     
  21. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Thanks everyone, and appreciate it's next to impossible to give opinions second hand with no photos.
     
  22. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    In any event, lack of bonding of services is potentially dangerous and needs to be implemented a.s.a.p. It is TN-C-S. The three neutrals into one needs further investigation and appropriate action taken to rectify if needed, which I imagine it certainly will be. You seem to have proved the Zs is satisfactory so therefore will meet required disconnection times assuming you did Zs on up and down ring. You did not mention the Pfc, which might be interesting to have a stroll around to ensure equipment installed can take the fault current.
     
  23. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Cheers. I'll certainly have another look and check pfc as well.
     
  24. Leesparkykent
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    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    You done Ze and said it was 0.19 Ohms.. As its TN-C-S PEFC and PSCC will be the same so the calculated PFC=230V/0.19 Ohms...which is 1210A
     
  25. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Sorry my mistake. The Ze was 0.3. I did a quick pefc I think it was, and it was nice and high. Could've been 1600amp.

    It was my house that was 0.19Ze and that's definitely a tns.
     
  26. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    You cannot base the earthing system from a Ze
     
  27. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Sorry just meant it is visually unambiguously a tns at my house. And low ze. I'm confusing the issue just ignore that!
     
  28. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    she's holding on to them. can't believe it. nesting but not dropping yet.
     
  29. Pete999
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    Pete999 Trusted Advisor

    Top Poster Of Month

    Location:
    Northampton
    Typical always keep you waiting, sleepless night ahead then?
     
  30. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    With Amd 3 pfc is calculated as 230 x.95 (Cmin) = 218.5/0.3 = .73 Ka (pg. 127 GN3) Not that it makes much difference but it certainly would if you had 0.03 which is becoming more common. I think you need to set your loop test to high output as no trip loop test can be innacurate especially on Ze test.
     
  31. Murdoch
    Online

    Murdoch Electrician's Arms

    Location:
    Woking
    FWIW there is NO requirement to upgrade the CU tails to 25mm, especially as you've confirmed the main fuse as 60A
     
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  32. Jay Sparks
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    Jay Sparks Trusted Advisor

    Location:
    Bratford
    How do you know the water and gas needs bonding? Have you tested them?

    Jay
     
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  33. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Thanks everyone. Plenty for me to think about which is exactly what I need!

    My understanding is any incoming metal service pipework needs to be earthed regardless? Incidentally, just found out my friend was charged for the bonding and meter tails upgrade whatever the requirements are!
     
  34. Des 56
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    Des 56 Trusted Advisor

    Location:
    Gliese 581C


    "Bonded"
    shinypen,Bonded

    He was more than likely stung by a not too rare company which has been badged by the naughty Niceic money grabbers
    Maybe the type of courses that enable registration these days promotes standards that are questionable all too often
     
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  35. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Think there will come a time when you are better off using a contractor not in a scheme.
     
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  36. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    Cmin isn't factored into PFC measurements. If anything for PFC you would be concerned about Cmax which isn't even defined.
     
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  37. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    Better tell the people who wrote GN3.
    • Fault current, I = U0 × Cmin /Zs
    where:

    U0 is the nominal voltage to Earth,

    Cmin is the minimum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations.
    Pg. 127
     
    Last edited: Mar 18, 2017
  38. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    I don't have my copy on me at present to verify this, but remember this is only a guide book and does not form part of the Wiring Regulations, and indeed may contain errors!
     
  39. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    @Risteard@Risteard If you look in the regs at 411.4.5 411.5.4 etc. and onwards you will see Cmin is factored in to Zs x Ia < Uo x Cmin. Although they dont actually give that formula it is clear in BS7671 it is meant to be factored in by impication. btw I quoted the GN3 verbatim and page number. Although I do agree the Cmax factor may be more appropriate as a safety margin.
     
  40. Richard Burns
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    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    There is a difference between the prospective fault current and the fault current calculated from the I = U0 × Cmin /Zs formula.
    In the second case this formula is being used to determine the trip time of a protective device and so should be the lowest value of fault current that may occur on the installation.
    Where you are determining the prospective fault current this is to ensure that the protective device an handle this current so you are determining the maximum expected value that may occur on the installation.
    Any protective device must be capable of operating quickly enough at the lowest fault current and also capable of withstanding the highest fault current.
     
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  41. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Cmax is given a figure of 1.1.
    Normally used when you want to calc fault current between phases at design stage.
     
  42. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    Where?
     
  43. shinypen
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    shinypen Regular EF Member

    Location:
    Wales
    Just as a follow up. Had another look today.

    The 3 neutrals in to one were actually as follow: 3 x 1.5mm in to one 2.5mm. The mcb was 6amp so not actually dangerous if a little lazy???

    There was definitely no bonding in place even though he'd charged for it and recorded it on the cert. Thanks.
     
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  44. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Iet 17th edition design guide
     
  45. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    Which comes from IEC documents - my point stands that Cmax is not a defined term within BS7671. (I don't believe even the IEC document refers to it by that name.)
     
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