As I outlined in a couple of earlier threads, I want to do some electrical work on a property recently bought by my son. Because it was discovered by the electrician who fitted a new CU that there was no earth to the lighting circuit, I intend to completely rewire all the ceiling roses and switch drops - as well the exterior lights at the front and rear of the property. In addition, also I want to replace the 'over the bath' shower for him with a 9.5kW unit. When I have completed all of this I want to get the electrician back to check and test everything and (hopefully) issue a certificate that everything is in order and up to 17th Edition standards.
Although I have spent my entire life in the electrical/electronics industry - the latter part in industrial control systems - I am not an electrician and make no claims to be either an expert in domestic installations or entirely conversant with 'The Regulations', so this is why I am seeking some advice here from those that are. Am I correct in thinking that under the 17th Edition all circuits need their own separate 30mA RCD? What information I have been able to find leads me to believe this to be the case, but if this is not entirely correct then would a shower need to be wired through its own RCD?
I know that previously some lighting circuits were often not RCD protected - the reasoning being that in the event of someone coming into contact with a live conductor, and tripping the RCD, it was quite rightly considered dangerous for the whole house to be suddenly plunged into darkness. I understand that recent changes in the 'regs' still have that situation very much in mind, but now insist that all circuits are protected separately. What are the requirements?