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RCD socket outlet.

Former Community Member
Former Community Member
Hi all,
Any comments on this one most welcome!
A customer wants me to replace an existing one gang 13 amp socket outlet with a double.
The problem is that there's no rcd protection there, so i'm thinking that as I am in effect adding a socket outlet I should fit an rcd protected one?
If I were replacing like for like it wouldn't bother me at all but the fact it's going to be a double makes me think an rcd protected one is the thing to do, just seems a bit ott to fit one rcd protected socket when there are probably 20 others that aren't rcd'd!
  • Former Community Member
    0 Former Community Member

    gkenyon:




    weirdbeard:



    Hi John, BS 7288 wasn't listed in appendix 1 of the 2008 17th edition, and here is a related topic from ye old forum:

    https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=28346


    Would you mind explaining why this has fairly recently become an issue that you hold dearly? ps, you seem to be struggling to get your new board fitted, I have a couple of hours spare next week if you need any help :)


     


     




    BS 7288 itself has been updated.


    The current version of BS 7288 does not have the same provisions as the previous version, and, in addition, attempts, perhaps somewhat clumsily, to interpret BS 7671 using a mixture of terminology ... and further clearly says that additional protection must already be present in the circuit in which it is installed.


    So, this isn't just BS 7671 we're discussing here, but the product standard itself.


     




    Thanks for replying GK, but if The product BS was not listed 10 years ago in BS7671, I am not entirely sure how it is more relevant that is still not included in the latest edition! 




     

  • 0

    Sparkingchip:

    The house that Dave is asking about was presumably installed as EEBADS without any RCD protection in the consumer unit or fuse board at all, indeed it is still possible to install some circuits in homes without RCD protection, though not lighting circuits anymore as they require RCD protection as of this year.



    Andy makes a good point. RCD is not the cure for everything. Despite JP's remonstrations, I am happy with my 15th Edn installation. However, I do acknowledge that it does not provide protection from, for example, that frayed cable on Mrs P's iron that she has not mentioned. ??
  • 0
    We made that transition from EEBADS- Earthed Equipotential Bonding and Automatic Disconnection of Supply to ADS- Automatic Disconnection of Supply.


    The house that Dave is asking about was presumably installed as EEBADS without any RCD protection in the consumer unit or fuse board at all, indeed it is still possible to install some circuits in homes without RCD protection, though not lighting circuits anymore as they require RCD protection as of this year.


    So it is more than feasible that you could be called to a house where people are getting electric shocks off the kitchen tap, because someone messed up replacing a light fitting on a  non-RCD protected light circuit and the requirements for EEBADS was not fulfilled or has been compromised.At the very least an electrician can be expected to do an earth fault loop test when replacing a light fitting and anyone else should confirm earth continuity in some other very basic way. It could happen the other way around, someone could replace a light fitting then get shocks off it due to an existing fault elsewhere.


    So replacing a light fitting or anything similar still requires some basic inspection and testing; and yes the closer the a RCD that may be installed is to the electric suppliers intake, and the more circuits it protects, the safer the installation will be and putting the RCD at the end of the circuit is the least favorable choice.


    I have walked away from jobs like the one Dave asked about after the customer declined to have main protective bonding conductors installed along with a new consumer unit, at one house the customer said I don't want those I will just have the extra socket. Someone else wanted some new sockets installed in a TT installation protected by an ELCB that had had its earth rod removed, when i mentioned having to have a new consumer unit and earthing installed she got all uppity with me and said she had just had her kitchen rewired by the kitchen fitters and they had not said there was anything wrong with it and she wasn't going to pay for anything other than the new sockets she wanted in the bedrooms for her lodgers to use. Installing SRCDs in either of those homes would not have resolved the fundamental problems.


    You have to know when it's time to walk away, if an installation was not safe thirty years ago just bunging in random RCDs is not going to make it safe now.


    There is a time and a place for installing SRCDs and FCRCDs subject to other criteria being met, but those who wrote the British Standard for them don't appear to identified when and where that is.


    Andy Betteridge.
  • 0

    In the GN it actually says:

    13.2.1

    The effect of applying main protective bonding is most noticeable in TT systems



    or to put it another way, in some circumstances with a L-PE fault internal to the installation, main bonding in a TN system provides little more reliable benefit than a chocolate tea pot.


      -  Andy.
  • 0
    I find bonding extraneous-conductive-parts and exposed-conductive-parts very satisfying in locations like bathrooms or shower rooms etc. It is a kind of passive, reliable,  bullet proof protection method, until meddled with by others such as D.I.Y.ers or plumbers. It has no moving parts, and is normally quietly active and on guard 24/7. It is to be recommended.


    Z.
  • 0
    I did look at the IET Guidance Note and Graham is acknowledged for his contributions on page 6, So has a far more detailed knowledge of its contents than the rest of us.


    In the GN it actually says:

    13.2.1

    The effect of applying main protective bonding is most noticeable in TT systems.


    Going back to the discussion, a RCD won’t protect you from faults upstream of it, so the earthing and bonding needs to be sound to reduce touch voltages downstream of the RCD from faults up or down stream of it.


    You don’t want anyone to die in the bathroom because there is a faulty electric heater in a bedroom, has as happened.


     Andy Betteridge 


  • 0
    415.1.2


    Z.
  • 0

    Sparkingchip:



    Maybe the saving grace is that bonding is more effective in reducing touch voltages in TT installations than in TN installations.


     Andy Betteridge 


     




    Well, that's only partly true. Bonding only works to reduce the touch voltage for TT within either:


    (a) a notional "zone of influence of the earth electrode",


    or


    (b) within what we used to call the "equipotential zone" of the bonding system.



    In all other cases, the touch voltage in a TT system may well approach U0. This might even include indoors in certain situations where the bonding doesn't control the touch voltage - but almost certainly includes most situations outdoors at distances above 3 m from the earth electrode or buried extraneous-conductive-parts (depending on the type and composition of the electrode or extraneous-conductive-part of course) ... and I think this is the answer to your question regarding 25 V touch voltage for construction sites - not practicable?


     

  • 0

    AJJewsbury:




    That is exactly the point I was making, you cannot connect a RCD to a circuit and installation that is not adequately earthed and bonded or else a fault elsewhere in the installation may raise the voltage of earthed equipment downstream of the RCD to dangerous levels, a RCD does not remove the requirements for basic and fault protection along with the requirement to mitigate touch voltages.



    The point I was attempting to make was than even in a fully correctly earthed & bonded installation a fault elsewhere can raise the exposed-conductive-parts downstream of the RCD (as elsewhere) to dangerous levels - e.g. >115V for 5s in a TN system or 230V for 1s in a TT system -  the 'mixed disconnection time problem' isn't just something for inadequately earthed/bonded installations to worry about.


    There is some advantage in having all your RCDs close to the MET (with the minimum of parallel paths on the c.p.c.s) - in that faults on your circuit are covered by the rapid disconnection time of your RCD and faults on other circuits shouldn't raise the potential on your c.p.c. relative to the MET (where both your c.p.c. and main bonding are connected) - but BS 7671 doesn't clearly advocate that approach (although perhaps hints at it in section 701).


       - Andy.

     




    Maybe the saving grace is that bonding is more effective in reducing touch voltages in TT installations than in TN installations.


     Andy Betteridge 

  • 0
    Question.


    Did the JPEL committee ever discuss making a single upfront 30 mA RCD a requirement for all domestic installations? Rooting around the internet I have seen a comment that they did, which would make sense as it makes for the safest installation.


    Another question.


    When was the requirement for a maximum touch voltage of 25 volts for a construction site installation dropped and why?


    Andy Betteridge 


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