Discuss N/E fault RCD not tripping ?? in the Electrical Forum area at ElectriciansForums.net
If you know there are usb sockets in the circuit, testing N-E insulation is a bad idea.
you can't say there is a dead short if testing with an insulation resistance tester.
I would only consider something to be a dead short if measured below 1 ohm.
The USB installation blurb differs between brands. I fitted a LAP usb socket and it states that you can do installation test at 500 V but others state that they must be disconnected.But regarding the USB sockets. If I have not disconnected the neutrals from neutral bar and tested between live and earth and I am getting low reading basically zero near enough, this should be because the USB points are bringing the reading down as I will be going through the earth and being TNCS will be linked to neutral so will be testing the USB point. As when I link out live and neutrals at the consumer unit and go to a socket then test live to earth insulation resistance it comes out clear. >999mega ohms. Now if that was a damaged cable that would be picked up, does that make sense ?
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