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Dual RCD boards are unlikely to be suitable for EV charging installations even with type A or B RCDs, discuss

IronFreely

I’ll paraphrase Regulation 722.531.3.101, “each charging point shall be protected individually by an RCD”. With that in mind a dual RCD board where both RCDs protect multiple circuits will not be suitable as the requirement is for the charge point to be individually protected. The reason I open this up to discussion is because so many installers seem completely unaware of the wording of 722.531.3.101 as about 50% of the installations I see the charger is protected by an RCD protecting multiple circuits, in particular new builds were the provision for electric vehicle charging has been made during development. I also often give quotations to prospective clients where they’ve already had at least one quotation where the previous installer has said “great you’ve got a spare way in your dual RCD board, so we can use that” and I’m thinking “erm no you can’t”

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  • what tends to happen is they install an SWA cable on a 32A MCB which is terminated on the driveway in a wiska box… technically it’s fully compliant as it would only be non compliant when the charger itself is installed…

    Am I missing something here? Provided the EVSE has 30mA RCD protection included - which most seem to claim they do (presuming it does actually comply with the required standards, which has been questioned for one or two models) wouldn't 722.531.3.101 be satisfied even if the circuit was fed by an MCB?

       - Andy.

  • in reply to AJJewsbury

    Some new house/flat builders do not know what they are asking for or how to check.  They don't know, that they don't know.


    So lets break it down for them.

    Cable from CU to EVSE point (Wiska Box). 2.5mm2 CSA SWA is not the same as 6mm SWA or a 6mm EV-Ultra.  The Ethernet cores in the Ultra can be used for CT or load management or load shedding.  A 2.5mm SWA may be compliant and be classed by the Marketing people for the house seller as EV ready.



    In the CU/DB a MCB is not the same as an RCBO.  Now that we are talking Residual Current what use is a 30mA type AC in a dwelling.  Still being fitted as we speak/type.  It needs to be a minimum of type A.  A Blank or MCB or RCD type AC may be compliant and be classed by the Marketing people for the house seller as EV ready.


    The last one which makes me chuckle.  A Wiska box (other brands are available) on the outside wall and no EVSE insight without having to pay more.  It may be compliant and be classed by the Marketing people for the house seller as EV ready.

  • in reply to AJJewsbury

    I have recently completed the installation of a 22kW charging unit which purports to include Residual Current Device (RCD) protection, specifically an AC 30mA type and DC 6mA. However, it does not conform to any established British Standards, such as BS 61008; consequently, the installation of an additional RCD at the circuit’s origin was necessitated to ensure compliance and safety

  • in reply to Sergio Fernandez

    I'm guessing the 2.5mm cable is intended to be terminated in an EV-rated 13A socket, and they can say "job done".  The householder can now use their granny lead to charge the car.

  • in reply to Simon Barker

    Using a Granny Lead (Poor choice of name in my opinion) would take days to charge an EV but it is an accepted method when there is no other option as a get you out of a predicament  Its not a long term solution.

    The other thing to consider is the average home buyer does not know what an EVSE is and they do not know what to look for.  So when the marketing brochure state EV ready they Assume rightly or wrongly it means ready to just park your vehicle and start to charge it. 

  • in reply to Sergio Fernandez
    Sergio Fernandez said:
    The other thing to consider is the average home buyer does not know what an EVSE is and they do not know what to look for.  So when the marketing brochure state EV ready they Assume rightly or wrongly it means ready to just park your vehicle and start to charge it. 

    Are people really so gullible?

    Perhaps they are 'cos the show houses are bound to have been fitted with an EVSE.

    Back to the CU ...

    Does it really matter because if the installation has been done properly and appliances are fit for purpose and well-maintained, nothing should ever trip.

  • in reply to Chris Pearson

    The average person does not know or understand Electrics.  They pay an electrician who they Assume (rightly or Wrongly) does the job correctly and to the current standards/regs of BS7671.

    Now the issue is that sometimes the Sparky or the Designer do not know what is what or there is confusion or mis-leading/mis-guiding information.  Controversial statement I know.  Eg. Take a domestic dwelling RCBO.  
    MCB Trip curve B eg a B6 and RCD Class A or Type A
    Now look at the front of an RCBO and it states B6 so some people think or may think they have a RCBO type B.  Bargain at only £15 to £20.  The informed people will say the B6 is the MCB side and the icons will tell you the RCBO side.  Then there is the other elephant in the room.

    Single Pole

    Double Pole

    Single Pole with switched neutral or solid Neutral

    Again this could confuse us on the best of days. 
     

  • in reply to Sergio Fernandez
    Sergio Fernandez said:
    Now the issue is that sometimes the Sparky or the Designer do not know what is what or there is confusion or mis-leading/mis-guiding information.  Controversial statement I know.  Eg. Take a domestic dwelling RCBO.  
    MCB Trip curve B eg a B6 and RCD Class A or Type A
    Now look at the front of an RCBO and it states B6 so some people think or may think they have a RCBO type B.  Bargain at only £15 to £20.  The informed people will say the B6 is the MCB side and the icons will tell you the RCBO side.  Then there is the other elephant in the room.

    This example of "confusion" cannot be addressed in BS 7671 ... marking and classification of circuit-breakers, RCCBs and RCBOs is mandated by the relevant product standards.

    You will notice that there is no real confusion, though, in terms of marking on the product ... B on an RCBO does not relate to classification of residual current operating characteristics, which are identified by one or more relevant symbols, as illustrated in Guidance Note 3 here:

    So, is the confusion actually coming about in the technical specifications and descriptions?

  • in reply to gkenyon

    Is the above explanation made clear in the latest OSG (On Site Guide) I do not have one to hand?

    People find the explanations in the OSG easier to understand than BS7671 and often the OSG is their Go To reference guide while on site

  • in reply to Sergio Fernandez

    I don't think so, that Figure is from Guidance Note 3: Inspection & Testing, 9th Edition.

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