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Caravan RCD trip power connections

Paul R
Dear all , a holiday question


I have an acquaintance who asks why his IET 18th Edition RCD tester when plugs it in to the Local RCD (<30mA/300mS) , the primary supply RCD trips (that is further up the AC supply line) , rather than the caravan’s, so in effect nullifying the test.

Is this because the Primary Supply RCD  is monitoring a small standing current from other connections and the Local RCD needs to be tested by using the Local Earth at the unit ? ( which is not so easily accessible). 


Are there any other thoughts please ? 


Paul , Swindon LN IET. 



Parents
  • 0
    So if you are treating the caravan as an appliance with a flex and plug you need to consider how to test the RCD. 


    When portable appliance testing you may need to test plug-in RCD devices, plugs and adapters. If you know what you are doing you can make up a fly lead testing adapter that uses the neutral as earth just for portable RCD testing and when for you are checking your own test meters, so you can do a high-loop test on a RCD protected circuit without the installation RCD tripping.

     


    The downside of that is that with Class I appliances, exposed-conductive-parts become connected to a live conductor. In the case of a caravan, the "chassis" is [should be] connected to PE, so that becomes connected to a live conductor also.


    In some existing premises, industrial socket-outlets are present which aren't yet RCD protected, because it wasn't a requirement in BS 7671 at the time.


    If I were looking what to do now, I think I would be leaning to RCD protection for the outlet the caravan is connected to, and do the "up/down" test in the caravan being the safest option?


Reply
  • 0
    So if you are treating the caravan as an appliance with a flex and plug you need to consider how to test the RCD. 


    When portable appliance testing you may need to test plug-in RCD devices, plugs and adapters. If you know what you are doing you can make up a fly lead testing adapter that uses the neutral as earth just for portable RCD testing and when for you are checking your own test meters, so you can do a high-loop test on a RCD protected circuit without the installation RCD tripping.

     


    The downside of that is that with Class I appliances, exposed-conductive-parts become connected to a live conductor. In the case of a caravan, the "chassis" is [should be] connected to PE, so that becomes connected to a live conductor also.


    In some existing premises, industrial socket-outlets are present which aren't yet RCD protected, because it wasn't a requirement in BS 7671 at the time.


    If I were looking what to do now, I think I would be leaning to RCD protection for the outlet the caravan is connected to, and do the "up/down" test in the caravan being the safest option?


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