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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”

  • in reply to Sergio Fernandez
    Sergio Fernandez said:
    May I suggest it gets added to OSG for the next revision?

    I will forward to the relevant department at the IET.

  • in reply to IronFreely

    I do understand that people should keep up with CPD..  It is not always the jobbing Spark doing it.  Some times the Designer is getting it wrong and the installer just go ahead with what is on the plan or diagram.  Sometimes the installer is not fully qualified or competent and they may be 1 of 10 with only one QS on site. 

    This also brings up an interesting discussion.  Lets say the Designer or installed read the MI (manufacturers Instruction) for MyEnergy Zappi 2 to 3 years ago or they went on the installer course.  Now we know the Zappi does not comply to BS7671 with regards to the RCD protection so MyEnergy are now telling customers the Installer done it wrong.  However the Installer followed the MI issued at that time for the install done at that time. 

  • in reply to Sergio Fernandez

    This is just a matter of keeping oneself well informed of what is required in terms of personal CPD… up to a point competency schemes should be on top of it as well. 
    There’s no excuse for a jobbing sparks to not know what a B type RCBO with A type RCD characteristics is, and the difference between double pole, single pole (solid neutral) and switched neutral are and how to identify the symbols on the devices… after that it’s about being aware of which ones you as an installer need for the kind of installs you do.

  • BS7671 does not need to ban dual RCD split load consumer units, because the majority of them have three neutral bars allowing them to be split three ways with a non-RCD protected busbar adjacent to the main switch for MCBs, RCBOs or AFDDs to be installed for specific circuits, as well as the two RCD protected busbars for general circuits.

    That is what I installed at home around fifteen years ago, it’s not a new idea.

    www.consumerunitworld.co.uk/what-is-a-high-integrity-consumer-unit-and-how-to-populate-it-331-c.asp

  • in reply to gkenyon

    May I suggest it gets added to OSG for the next revision?

  • in reply to Sergio Fernandez

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

  • 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
    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 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:
    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.

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