I have been following a heated debate on this subject ,its been suggested to I.R test circuits before cu change.if doing so are you testing through main tails or individual circuits both would involve lamps out sockets and appliences dissconnected this would take time and could risk damage to sensitive circuits that you have missed, i put a tong meter on the main earth tail from the cu to the meter and check to see if there is any amps present if so i have a earth fault on the installation i would then scale down testing to find the circuit with the fault this of cause would not show up if the cu has no rcds but would as soon as you fire up the nice new cu with nice new rcds it works for me i am at present on 2391 and this subject is a good one
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