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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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    It begs the question as to why the manufacturer chose to go for the higher design parameter or did they just turn out that way?


    Andy
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    Sparkingchip:

    It begs the question as to why the manufacturer chose to go for the higher design parameter or did they just turn out that way?


    Andy 




    With regard to RCDs I think Hager's interpretation of  536.4.202, 531.3.3 and 415.1.1 means they are offering consumer units with RCDs that are 100A -  Type A -  30mA (in a two module form factor). Whereas Wylex and MK seem to have taken a different approach with Wylex offering boards with a 80A  - Type A - 30mA and can't see boards from MK with type A. (other manufacturers are available ?)


    I am guessing that there may have been some design limitations to achieve the characteristics Hager wanted (i.e. 100A - Type A - 30mA - two module form factor), which meant that the trip time and trip current are on the thresholds of the BS EN 61008-1.


    It would be interesting to test some other manufacturers RCD (100A - Type A - 30mA - two module form factor) and compare results.

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    mapj1:

    So a test current of 70mA at 230v then ( R= 230V / 3.3k ohms)

    as I said, neither 30mA nor  5 times it, just something to make it trip.

    Presumably those are marginal for use at 110V as well as 230V, although at 30mA test current would be only just about OK.

    Of course a good 30mA RCD fires at about 20-25mA so really it is fine.




    Note to self. Always tighten up the cage clamp screws before testing the resistance of the internal test circuit of an R.C.D. or the loose terminal clamps may not actually connect to the fixed terminals, and the screw heads may be completely electrically isolated, thus provide a false test result of open circuit.


    A Schneider DIF263300 2P 63A 300mA-A (Type A) R.C.D. reads 0.364kOhms across the test circuit with the button pressed in.


    Z.


     

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    Given that they could have chosen any resistor value for the self test, and parts with a 5% tolerance cost pennies and 1% tolerance only a bit pricier, even laser trimmed 0.1% are not that dear; I'm sure there is a deliberate  intention to set the 'self test' current a bit high, or perhaps to be more charitable, it may be to  make sure the same design can be used for  110V as well as 230.

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