O
oldtimer
Well done at least you found it and thanks for letting know
Discuss RCD Problem in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net
If it's affecting all 3 conductors it sounds like a JB which is wet or a choc block buried in plaster. Like Handyspark says use the low res ohmmeter. Could even be mice chewing through the PVC under the boards.
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