Thats what I thought but was more concerned with using a single conductor to combine N and Cpc I would have thought could upset an rcd.
Residual current devices (RCD) rely on detecting currents flowing in the earthing conductor by measuring the out of balance currents between phase and neutral conductors. In a TN-C installation, the neutral and earthing conductor are combined, thus making the detection of residual current impossible.
You cannot tell what is a legitimate neutral current, and what is an earth fault current using the PEN, as the earth and neutral combined.
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