Dont undersell yourself, you will still have some uses even though your knowledge is limited. In time you will gain valuable experience and be alot if use to a company. Your offer would also probably be illegal with minimum wage laws now in place.
Could you not convince the client to have a wired speaker instead so that they can use either their own hi-fi (do people still own these?), or other audio device to connect to it?
Thats awful, maybe its a blessing in disguise if they cant see you have passed it but just waiting for a certificate which tells them exactly the same thing.
The OP worded the question as though the works had been carried out, its now a lot clearer what has happened. Given that they say the max Ze of a TN-C-S can be 0.35 it has been badly designed from the start.
What do you mean you have done everything to lower the values? Either installing a larger earth cable to the submain or swapping the OCPD will ensure it complies.
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