Country hotel - shower upgrades and voltage drops

[sometimewoodworker]

11 hours ago, NilSS said:

As I said, I'm not qualified or certified, but I guarantee that anything I personally do is of an infinitely higher standard than ANYTHING I've seen in Thailand in 20 years.

Often good advice and true, but professional qualified  electricians  are around though extremely difficult to find I agree.
 

But once found they do top class work (and get good money for it). So in the Udon area I know 1 for weekend work (his day job is with medium to high voltage cables at the PEA) and can refer him and his small team, with photographs of work done. He also guarantees his work.

[IDug]

15 hours ago, NilSS said:

I'm not going to say anything is OK without seeing it or installing it myself. One of the problems is you're dealing with a wet room, which should be an equipotentially bonded safe zone. Messing around with multiple ground rods or (multiple paths to ground) is just asking for trouble.

Thanks very much NilSS, all your comments are useful and I understand that I should use them as heads-up on potential problems rather than as instructions on how to go forward. I have had another look at the setup on this building and it looks like it will not be a big job to put the new wiring through the existing CU so I will get the electrician onto it.