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Regulation stating a type AC RCD can not be upstream from a type A RCD

Alan B

Hi

I found an EV charger today with built in type A RCD + RDC-DD connected to a type AC RCD in the consumer unit, the AC RCD is also protecting 3 other circuits including sockets. I know this is incorrect because the type AC RCD could be blinded by DC currents, but I am struggling to find a regulation to reference when providing information to the customer?

Thanks

Alan

Parents
  • 0

    but can you describe that current on the mains side of the full wave rectifier, it is not DC is it?

    No, but it has a d.c. component though doesn't it? Just like the D-loc system...

       - Andy.

  • 0 in reply to AJJewsbury

    D-lock, is that when my MFT juices up the RCD so I can do a live Zs test?

  • 0 in reply to IronFreely

    Originally a new feature in the 1990s Robin loop testers had 'D-Lock' where the pushed  a high-ish and very smooth DC round the N-E loop to blind the RCD to allow an L-E Zs test not to trip it.The DC was ramped up over a second or two.

    Meggar and others went down the route of very small test currents and funny waveforms and averaging over a long time instead.
    Of course sometimes the RCD tripped anyway, and sometimes the funny waveform stuff does not read what a 50Hz sinewave would see.

    Mike

    PS Robin also patented the funny waveform idea as well both patents are expired and so the idea is 'free' and maybe worth a read.

    Patent1 DC injection  1987

    Patent2 funny waveform  1996

  • 0 in reply to AJJewsbury

    From Wikapedia Direct current (DC) is one-directional flow of electric charge.So the output from a bridge rectifier would meet this definition. I have seen it described as pulsating DC. I wonder if pulsating DC has a different impact on an RCD coil compared to smoothed DC.

  • 0 in reply to mapj1

    Most interesting. A good find.

    Drawings (espacenet.com)

    Z.

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  • 0 in reply to Zoomup

     

    truncated link - what were you aiming to link to.

    Mike

    PS patent searches are a very useful tool sometimes

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