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RCD Testing x5 150mA (or higher for Hager RCCB)

sparkiemike
Following on from John Peckham's recent post, I have recently installed several of Hager's consumer units with their new 100A 30mA Type A RCD (CD285U)


When testing the RCDs I noticed the trip times were much higher than previously experienced. Hager have said that RCCB needs to be tested at 250mA https://www.hager.co.uk/news-exhibitions-case-studies/18th-edition/updated-guidance-rccb-testing/97806.htm


In addition, if you have a Fluke you may notice that when carrying out a earth loop test (in no trip mode) the Fluke will fail to get a reading and trip the RCD. Apparently Hager have had a several reports of this and when I called could not explain it.
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    davidwalker2:

    I have always assumed that pushing the test button on an RCD or RCBO injects a fault current of 30mA.  I am now wondering if that is so, and that it is actually 150mA


    David




    Ah well usually it is neither  - for RCDs that may run on 110V or 240, the test resistor is set to be well over 30mA even at 110V.  Actually  for RCDs with a real test resistor inside that gets put between outbound L and inbound N, or v/v if you have a general purpose meter with a resistance range covering K ohms, then you can measure it on the bench, meter probes in the appropriate L-N and press the test button.


    Usually more like 100mA 2,2 k ohms ish.

    note that on some electronic RCDs and RCBOs, the push button goes to an on board microcontroller that in turn fires the trip, so only testing the mechanics can move, and  not the current sensing aspect at all, so metered tests do have a purpose.

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  • 0

    davidwalker2:

    I have always assumed that pushing the test button on an RCD or RCBO injects a fault current of 30mA.  I am now wondering if that is so, and that it is actually 150mA


    David




    Ah well usually it is neither  - for RCDs that may run on 110V or 240, the test resistor is set to be well over 30mA even at 110V.  Actually  for RCDs with a real test resistor inside that gets put between outbound L and inbound N, or v/v if you have a general purpose meter with a resistance range covering K ohms, then you can measure it on the bench, meter probes in the appropriate L-N and press the test button.


    Usually more like 100mA 2,2 k ohms ish.

    note that on some electronic RCDs and RCBOs, the push button goes to an on board microcontroller that in turn fires the trip, so only testing the mechanics can move, and  not the current sensing aspect at all, so metered tests do have a purpose.

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