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Caravan RCD trip power connections

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.

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0 ebee over 4 years ago

If you have two non delayed RCDs cascading it could be one or the other or both that trip

If one is delayed then it should trip last or not all , however you really need to densitive by a factor of three to be sure i;e:-

10mA standard & 30mA delayed.

30mA standard and 100mA delayed.

for example

If you test the upstream one on its own and get readings then there is a little trick you can do to bypass it to test the downstream one. But you need to know what you are doing otherwise potentially dangerous
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0 ebee over 4 years ago

If you have two non delayed RCDs cascading it could be one or the other or both that trip

If one is delayed then it should trip last or not all , however you really need to densitive by a factor of three to be sure i;e:-

10mA standard & 30mA delayed.

30mA standard and 100mA delayed.

for example

If you test the upstream one on its own and get readings then there is a little trick you can do to bypass it to test the downstream one. But you need to know what you are doing otherwise potentially dangerous
Cancel
Vote Up 0 Vote Down

Cancel

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Caravan RCD trip power connections

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