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RCD x 5

lyledunn
apologies if you are already aware of this but with respect to the x5 or greater test current introduced in the 18th, Hager have advised that their RCBO units are manufactured to the 2017 amended version of BSEN61008/9 which permitted disconnection within 40ms at 250mA. Thus they advise testing at x 5 on both sides with the instrument set for 50mA on the variable range.
  • 0
    Thank you for the 'heads up'.

    It seems to me that the performance we allow RCDs  to achieve in the field is being rolled back  apace, now there are more of them in service.


    Of much more use to anyone receiving a shock is to know if they will ever be disconnected at anything less than 30mA ?


    Given that we are moving towards the high current test only,  and not making compulsory testing at 30mA to  recommend this is a 250mA test current for a device we in the next breath claim is for safety of life is actually quite a step. A shock situation where more than 250mA flows through a victim is a pretty  extreme case, and will involve large areas of live metal ,  immersion in salt water or damage to the outer skin,  allowing metallic contact to be made to  the much wetter and conductive material underneath (though that damage to the skin may for example be a full thickness burn through the epidermis from a much lower current applied over an extended period.)

    Anyway it is very interesting to see where the manufacturers and standards writers are taking us, and it seems to be away from shock prevention towards fire prevention only.
  • 0
    I hereby name this “The Hager sledgehammer test”.


    The Hager instruction to test at 5 X 50 mA is badly thought out as testers don’t have a 50 mA test as no one makes a 50 mA RCD, so it will have to be 1/2 X 500 mA unless you have a variable meter.


    Andy.
  • 0
    Shocking.

    http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.html


    It is more the skin/body resistance that limits the current magnitude, the R.C.D. hopefully limits the duration of the shock current.


    Z.
  • 0
    Interesting real life experiences of electric shocks with and without R.C.D. circuit protection.

    https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=4503


    Z.
  • 0
    There is a  reason I would have preferred  to see any regs simplification to have retained the low current tests, and if they had to , rather dropped the high current ones, not the way it seems to be going.

    It really is personal ?
  • Former Community Member
    0 Former Community Member
    The Megger 1471 tester has a setting "VAR" where you can add compensation to the test to apply the desired setting.

    Also not sure if I have read mike's comment correctly regarding simplification of regs but neither test have been removed. You have to use the correct time setting depending on what you are using the RCD for i.e. fault or additional protection and received rs this result. 

    ​
  • 0

    643.8 Additional protection

    The verification of the effectiveness of the measures applied for additional protection is fulfilled by visual inspection

    and testing. Where RCDs are required for additional protection, the effectiveness of automatic disconnection of

    supply by RCDs shall be verified using suitable test equipment according to BS EN 61557-6 (see Regulation

    643 .I) to confirm that the relevant requirements of Chapter 41 are met.
    NOTE: Effectiveness is deemed to have been verified where an RCD meeting the requirements of Regulation 415.1.1
    disconnects within 40 ms when tested at a current equal to or higher than five times its rated residual operating

    current

     




    My bold in the italics - now  to me,  and maybe to others, this says  'it is OK not to bother to check at the 30mA rating' Anything more than 5 times that would count as a pass, in principle even a test at many amps. ' That is an implication that I do not like.


  • Former Community Member
    0 Former Community Member
    That's correct. 5x for additional protection and 1x for fault protection
  • 0

    That's correct. 5x for additional protection and 1x for fault protection



    Why would you test at 1x for fault protection? L-PE faults will always have a significantly higher current than IΔn (typically least 4.6x if the installation complies with minimum TT requirements - normally much higher) and the times allowed for BS EN RCDs at 1x (e.g. 300ms) are insufficient for TT disconnection time on most final circuits where 0.2s is required.


       - Andy.

  • 0

    MS2000:

    The Megger 1471 tester has a setting "VAR" where you can add compensation to the test to apply the desired setting.

    Also not sure if I have read mike's comment correctly regarding simplification of regs but neither test have been removed. You have to use the correct time setting depending on what you are using the RCD for i.e. fault or additional protection and received rs this result. 




    So does the MFT1731.

    Here is the Hager guidance.


    I have just tested an RCD. It went 20 - 25% faster at 250 mA than at 150 mA. That is not a problem because the safe duration of a shock increases as the current drops. In any event, if a 30 mA RCD passes the test at 5 x IΔn, it follows that it will also pass at 250 mA, so just test as normal. If the trip time exceeds 40 ms at 5 x IΔn, then you would need to test again at 250 mA.


    Incidentally, it would be a mistake to think that a 30 mA RCD limits any shock to 30 mA.


    For large areas of (dry) contact, the hand-to-hand impedance may be as low as 1200 Ω, which gives a shock current of 200 mA. For small areas of contact, the impedance may be four to five times higher and the shock current of the order of 50 mA.


    It may very well be that if an RCD trips sufficiently quickly at 5 x IΔn or 250 mA, it must also trip sufficiently quickly at IΔn, but for my peace of mind, I would still wish to test at both values.

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