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Advice on compliance with regulations for new kitchen and general wiring question

Jamesb

Hi all, a couple of things:

1. We are looking at getting a new kitchen - live in old house with COB/brick/thatch construction for info. The kitchen fitter sent his electrician a pic of the current Consumer Unit which is a Wylex split load RCD, plastic case and he wants to replace it. The house wiring contains a mix of old and new wiring colours, but I had an EICR about a year ago to comply with my insurance requirements and it passed OK. Is there any good reason for requiring a change? He said something, via the kitchen fitter, along the lines of conforming with current regulations back to the fuse box. Is this really the case as I didn't think so from what I've read? I'm a chartered engineer, but only work on low voltage stuff so need to check what the situation is with people familiar with the regulations working on this day in, day out before I start querying this if it goes ahead.

2. One of the circuits has a 10A MCB feeding a junction box just below the CU which feeds through to some outside lights (old halogens no longer working via armoured cable outside) and a 13a socket just below the CU. The location of socket means it's really just used to plug in the hoover. Where does this stand with regard to the regulations? i.e. a 10A limited MCB feeding a 13A socket and outside lights? For info, I am intending to replace the old halogens with newer LED types so hardly any current there, but looking more closely at it I came to notice this. 

Thanks, James.

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    One more thing I forgot to mention. The house used to have a TT earth and was moved to TN-C-S in more recent times. When it was TT, the earth wire was connected to the MET and presumably they had that as a common point. The current arrangement is that the MET is not used and additional earths are connected to the CU earthing points within the CU box. Is there anything inherently wrong with this with regard to regulations?

    James. 

  • 0 in reply to Jamesb
    Jamesb said:
    The house used to have a TT earth and was moved to TN-C-S in more recent times. When it was TT, the earth wire was connected to the MET and presumably they had that as a common point. The current arrangement is that the MET is not used and additional earths are connected to the CU earthing points within the CU box. Is there anything inherently wrong with this with regard to regulations?

    Since 2022, BS 7671 recommends that a consumer earth electrode is connected to the MET of a TN-C-S or TN-S installation, so it should be connected back up if it's still there and in a serviceable state with a suitably low electrode resistance (usually comfortably under 200 Ω).  Would be of benefit if you want battery storage in the future, that has island mode (backup power) capability.

    It can be easier to carry out earth electrode testing if there's a separate MET block (with everything connected), especially if the earth electrode tests are being done with a clamp-tester and the wiring is otherwise hidden.

    Hopefully the DNO moved it to TN-C-S, and bonding was upgraded? There are a lot of DIY "TN-S" or "TN-C-S" conversions that we see posted on the Forum all the time ?

    Jamesb said:
    Is there any good reason for requiring a change?

    New/replacement socket-outlet circuits require arc fault detection devices (AFDDs) and surge protection (SPD) ... they may not be available for the existing consumer unit. Yes, you could have a second CU fitted if there is room ... we don't know, of course, whether there is room to fit a new one, and/or other circuits needing updating that may need AFDD ... but it could also be that, given the difference in cost, the space saving makes it a 'no-brainer'.

    Difficult to tell without more information - as you'll have seen above, there will be a lot of speculation and "if's" in the answers. Of course, there's the other factor of old wiring as you said ... very difficult without seeing it all.

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  • 0 in reply to Jamesb
    Jamesb said:
    The house used to have a TT earth and was moved to TN-C-S in more recent times. When it was TT, the earth wire was connected to the MET and presumably they had that as a common point. The current arrangement is that the MET is not used and additional earths are connected to the CU earthing points within the CU box. Is there anything inherently wrong with this with regard to regulations?

    Since 2022, BS 7671 recommends that a consumer earth electrode is connected to the MET of a TN-C-S or TN-S installation, so it should be connected back up if it's still there and in a serviceable state with a suitably low electrode resistance (usually comfortably under 200 Ω).  Would be of benefit if you want battery storage in the future, that has island mode (backup power) capability.

    It can be easier to carry out earth electrode testing if there's a separate MET block (with everything connected), especially if the earth electrode tests are being done with a clamp-tester and the wiring is otherwise hidden.

    Hopefully the DNO moved it to TN-C-S, and bonding was upgraded? There are a lot of DIY "TN-S" or "TN-C-S" conversions that we see posted on the Forum all the time ?

    Jamesb said:
    Is there any good reason for requiring a change?

    New/replacement socket-outlet circuits require arc fault detection devices (AFDDs) and surge protection (SPD) ... they may not be available for the existing consumer unit. Yes, you could have a second CU fitted if there is room ... we don't know, of course, whether there is room to fit a new one, and/or other circuits needing updating that may need AFDD ... but it could also be that, given the difference in cost, the space saving makes it a 'no-brainer'.

    Difficult to tell without more information - as you'll have seen above, there will be a lot of speculation and "if's" in the answers. Of course, there's the other factor of old wiring as you said ... very difficult without seeing it all.

Children
  • 0 in reply to gkenyon
    gkenyon said:
    New/replacement socket-outlet circuits require arc fault detection devices (AFDDs)

    I hope there is a 'may' missing between 'circuits' and 'require'.

    That is one of the few Regs that I cannot yet support. What are we, 4 years in now?, and we still dont know when, or if, they will trip when there is a faulty appliance. Anecdotal evidence has shown them to be trip happy, and also not trip when there is a genuine fault.

    The IET needs to show that they do work, rather than saying they recommend fitting them, without any evidence of their efficacy. If it was shown that they give a good, extra, level of protection within a dwelling, then no one would argue against them, but I have not seen ANY Manufacturers promoting how they work, and when they will work.

  • 0 in reply to gkenyon
    gkenyon said:
    New/replacement socket-outlet circuits require arc fault detection devices (AFDDs) and surge protection (SPD)

    Don't we always say that the Regs are not retrospective?

    I was quite happy to install SPD on the basis of discussions in here, but we have not had a problem since we moved here at the end of 1996. AFDD is a completely different matter.

    That said, I do understand that if you want to be bang up-to-date, you put in both.

    Anybody fancy £200 per circuit Eaton AFDD?

  • 0 in reply to alanblaby
    alanblaby said:
    The IET needs to show that they do work, rather than saying they recommend fitting them, without any evidence of their efficacy.

    Why 'The IET' ? If there is a problem with the product standard, that needs to be addressed, but also consider that BS 7671 is not 'written by the IET' ?

    alanblaby said:
    What are we, 4 years in now?

    No, 6 years. 'Recommended' since BS 7671:2018 for private domestic.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Don't we always say that the Regs are not retrospective?

    Yes, and I'm being quite inflammatory, using 'required' ... for private domestic (not in HMO or HRRB) they are 'recommended' ... you can conform to BS 7671 in not fitting AFDDs on socket-outlets circuits not covered by the list (HRRB, HMO, purpose-built student accommodation, and care homes) but they are still recommended

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