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AFDD Trip times

Former Community Member
Former Community Member
HI, just wondering how people are testing domestic AFDD'S 

I have been testing 30ma single pole AFDDs and im getting rcd disconnection times of roughly 80ms on 1x.

Is this normal? they consistently come up with around 80ms which is obviosly over the permissable 40ms.


my question is am i testing these wrong? is there a different way of procedure to test these devices? they are all the wylex brand if thats any help.


many thanks in advance for your responses
  • 0
    I saw in a youtube video that AFDD are normally slower than RCDs  i think its just how they are presumably they need to take several cycles to be sure its a real fault and not just a passing event
  • Former Community Member
    0 Former Community Member
    UK doesn't need AFDDs, for the matter all of the IEC world.



    But, carry on :)
  • 0
    I presume you're just testing the RCD element of a combined AFDD/RCBO.
    they consistently come up with around 80ms which is obviosly over the permissable 40ms.

    40ms is only required for 5x for 30mA RCDs - at 1x up to 300ms is permitted.


       - Andy.
  • 0

    UK doesn't need AFDDs, for the matter all of the IEC world.


    I'm inclined to agree, I'm not even convinced by the sparse data available from the US experience that they are all that especially useful in 110V land either, but neither of us are writing the UK regs.

    If we did they'd look a bit different.

    And there would not have been discussion threads like these where the need for AFDDs or otherwise is discussed at length.
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  • 0
    chrizzle86:

    HI, just wondering how people are testing domestic AFDD'S 

    I have been testing 30ma single pole AFDDs and im getting rcd disconnection times of roughly 80ms on 1x.

    Is this normal? they consistently come up with around 80ms which is obviosly over the permissable 40ms.


    my question is am i testing these wrong? 




    Yes.


  • 0
    Sparkingchip:
    chrizzle86:

    HI, just wondering how people are testing domestic AFDD'S 

    I have been testing 30ma single pole AFDDs and im getting rcd disconnection times of roughly 80ms on 1x.

    Is this normal? they consistently come up with around 80ms which is obviosly over the permissable 40ms.


    my question is am i testing these wrong? 




    Yes.




    ?


  • 0
    80 mS is no cause for concern at 1x as stated before 300mS for 1x with a modern RCD/RCBO
  • 0
    Unless it’s a final circuit in a TT earthed installation?
  • 0
    Sparkingchip:

    Unless it’s a final circuit in a TT earthed installation?


    Only if you have extremly poor Zs - a 30mA RCD should open within 150ms at 60mA (table 3A of appendix 3) - well within the 0.2s ADS requirement - which you'd get with Zs of up to 3833Ω - but then you'd be way over the 50V/Ia limit of 1667Ω anyway.


       - Andy.


  • Former Community Member
    0 Former Community Member
    mapj1:

    UK doesn't need AFDDs, for the matter all of the IEC world.


    I'm inclined to agree, I'm not even convinced by the sparse data available from the US experience that they are all that especially useful in 110V land either, but neither of us are writing the UK regs.

    If we did they'd look a bit different.

    And there would not have been discussion threads like these where the need for AFDDs or otherwise is discussed at length.
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    five

      M.




     





    Just look at the history. AFCI were soley created to deal with the lack of earth fault loop impedance in the US. UK wiring regs front and center stage in research. 


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