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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

  • 0 in reply to Sparkingchip

    Fleabay has new M.K. A type R.C.D.s at a very reasonable price.

    Z.

  • 0 in reply to IronFreely

    I relinquished my CEF account some 40ish years ago. Seems like nothing has changed with that company

  • 0 in reply to mapj1

    I believe it was called Tord4. I chose not to buy it on as I’d never heard of it before! Opted for a charger with built in RDCDD and A type RCD, supplied via MCB for fault protection and SWA for additional protection. 

  • 0

    Except that bridge rectifier has a smoothing capacitor on the output, so the DC has a rather indeterminate ripple, so may need a B type to be detected in all cases, the 100% unsmoothed (no capacitor) case is all that a type A is certain to trip on - though it may trip of course, and probably will so long as the DC is not too smooth, the problem is it is far from clear what that is.

    Or an A-type + RDC-DD? (what some manufacturers call an EV type I think).

       - Andy.

  • 0 in reply to IronFreely

    Thanks this one    costing this much ?  Given the Alibaba price of $37 plus shipping I can imagine £50 from an online store and a bit more from a real shop is about right. I have not used Wenzhou Tongou Electrical Co either, so in my book they'd have to rank beside Chint and a few others as not very familiar, use with caution, but that does not mean they are automatically bad, but unproven.

    Mike

  • 0 in reply to Zoomup

    A properly working appliance that prevents a type AC operating properly, Do you normally test RCDs with full load current? Not that that should matter, but it does if you claim that VSDs or whatever prevent proper operation.

  • 0

    I think that there is a bit of misunderstanding here, some are suggesting that a DC fault causes current to flow in the Earth conductor, but can you describe that current on the mains side of the full wave rectifier, it is not DC is it? PSPICE might help.

  • 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

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