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The last remaining domestic circuits without RCD protection.

Sparkingchip
I prepared an EICR this morning for a two bed flat.


The peak installation has a 30 mA RCD main switch, which surprisingly despite being more than ten years old is a type A, so no RCD issues there.


The off-peak supplies two storage heater circuits run in surface mounted plastic mini trunking without RCD protection, so again no RCD issues. If I were installing the storage heaters with new circuits I would install RCD protection, but there’s no reason to condemn an existing installation.


I am just pondering exactly what can be installed in a domestic installation now without any RCD protection with the 18th Edition of the Wiring Regulations making them a requirement on lighting circuits there cannot be much left on the list.


 Andy B.
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    Andrew Jewsbury:




    No, because the regulations are not retrospective.



    But the new work (fitting of the new luminaire) would need to comply with current regulations.

      - Andy.


    "need to comply"?


    So what if a customer asks me to fit a lumnaire and connect it to a non-RCD protected circuit? That could be because it is a lighting circuit which supplies solely lampholders (which are not, in my opinion, luminaires), or because it was installed to 17th Edn or earlier. Do I have to fit an RCD?


    If I cannot replace the existing MCB, or fit an RCD in a separate enclosure, that new CU is a nice little earner, but what sort of customer would accept that?


    The work would not comply with 18th Edn, but there is no requirement that it must do so. When you fill in a MEIWC (if you feel obliged to do so) you can comment under "Details of departures".


    Frankly, it is not necessary to bring an installation up to date every time that it is altered. That would be disproportionate and unreasonable.

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    David Strachan:

    Perhaps Mr Peckham is having a little laugh with us.




    I am sure that I can hear him chuckling in the background. ?

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    So what if a customer asks me to fit a lumnaire and connect it to a non-RCD protected circuit? That could be because it is a lighting circuit which supplies solely lampholders (which are not, in my opinion, luminaires), or because it was installed to 17th Edn or earlier. Do I have to fit an RCD?


    If I cannot replace the existing MCB, or fit an RCD in a separate enclosure, that new CU is a nice little earner, but what sort of customer would accept that?

     



    I would suggest the situation is comparable to earlier editions when the requirement for most ordinary sockets to have 30mA RCD protection was brought in. Where a extra socket was required on an existing non-RCD circuit, I think most people take the attitude that the new socket needed to have 30mA RCD protection - either by retrofitting an RCD for the entire circuit (more than absolutely required, but often preferable) or using an socket with a built-in RCD or starting the extension with an RCD fused connection unit.


    The work would not comply with 18th Edn, but there is no requirement that it must do so. When you fill in a MEIWC (if you feel obliged to do so) you can comment under "Details of departures".



    But you can only legitimately do that if you can show that the departure is no less safe than following the regulations (120.3) - generally (especially in an uncontrolled/domestic environment) I don't see how you can show that omitting 30mA RCD protection is just as safe as including it.


    Frankly, it is not necessary to bring an installation up to date every time that it is altered. That would be disproportionate and unreasonable.



    Agreed - however new work needs to comply - and sometimes upgrading (some of) the existing installation may be the most practical way of achieving that.


      - Andy.
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    Good points Andy,

    Agreed - however new work needs to comply - and sometimes upgrading (some of) the existing installation may be the most practical way of achieving that.





    In respect of the above, it's worth pointing out that either the electrical installation as a whole complies with the 18th Edition, or it does not, but that couldn't necessarily be said for a circuit.


    This is a good case in point, i.e. providing an RCD for a lighting circuit might bring the lighting circuit up to 18th Edition, but on the other hand, it is highly unlikely for at least some lighting circuits in existing housing stock, case in point being junction boxes under floorboards, which, all tests being fine, you wouldn't be rectifying to put in a new fitting or extending an existing circuit.


    So at this point, we are "cherry picking" what's to be brought up to 18th or not, and I guess the simplest approach is based on what Code you'd give it on an EICR.

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    When installing RCD protection to an existing electrical installation the safest option for reducing the risks from electric shock is to install an upfront 30 mA RCD main switch.


    The least safest option is to install a RCD protected switched fused connection unit for a specific item of equipment or a RCD protected socket outlet.


    Because the RCD only provides effective protection downstream of it.


    Also correct earthing and bonding needs to be in place.


    So if the installation was installed to an earlier edition of BS7671 and all the required earthing and bonding is in place, if the addition to an existing circuit is RCD protected from the point the addition is added on then presumably you can claim compliance with BS7671:2018 for the addition in respect of requirements for RCD protection for the new work?
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    Do you realise that if adding a spur to be RCD protected on a non RCD protected circuit then you must substitute an existing point for an RCD then connect your spur to it.

    it`s the only way to make the new addition comply via the RCD route.
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    David Strachan:

    Do you realise that if adding a spur to be RCD protected on a non RCD protected circuit then you must substitute an existing point for an RCD then connect your spur to it.

    it`s the only way to make the new addition comply via the RCD route.




    I see what you mean, but I am not sure that I agree.


    Assuming that we are discussing domestic premises, if it is an extension to a final circuit which the supplies two* or more luminaires, the whole circuit would need to be RCD protected (411.3.4). However, if it is any other final circuit, and the extension is supplying one or more sockets, it is only the socket which needs to be RCD protected provided that the new cable is not buried less than 50 mm deep, etc.


    *On a very strict interpretation: 411.3.4 refers to "luminaires" in the plural.

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    Yes that`s the thing,

    usually in such cases the cable between the existing point and the new RCD is less than 50mm deep. I am being pedantic

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