17th Edition requirements


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?
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The requirement is Part P of the building regs.
You can DIY it if you pay the council to inspect your work.
Adam
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Can I not pay a Part P qualified electrician to do that for me?
And, since I am only replacing an existing circuit, is even this absolutely essential? And the answer to the RCD question?
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Afraid not, and replacing a circuit is part P notifiable. IMHO you are better off doing the work and saying nothing. Your electrician will do a periodic inspection certifiacte for you if you want, he cannot do an installation certificate. .

Pretty much all circuits now need RCD protection. The minimum requirement is met by using a dual RCD CU with a mixture of lights and sockets on each RCD. A better approach is to use a RCD CU with some non RCD spaces on it and use RCBOs in these spaces for important cirucuits such as smoke alarms, freezers and some of the lights. The ultimate approach is to use all RCBOs.
Adam
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http://www.electrium.co.uk/Wylex17th%20Edition.pdf
gives you a bit of a guide as to the ways the 17th edition works with RCDs
What did your electrician fit? (dual rcd etc not make)
Adam
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First of all, thank you for your advice, Adam. Actually, I'm not exactly sure what the electrician fitted - other than it's a Hager CU. As I said, it's my son's place and I've only been there once since the job was done. I had thought about the RCBO route - but obviously there is a cost consideration there. Still not sure, though, if the shower needs its own dedicated RCD, probably fit an RCBO for that.
I must admit that I'm a bit surprised that you said replacing a circuit is Part P notifiable. I had understood that a straightforward replacement wasn't, but - as I said previously - when it comes to domestic installations I'm very much the amateur. Looks to me like I have two choices, take your advice and do the job and say nothing, or get the electrician in to do the lot. Have to think about it, but thanks for you advice anyway.
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Nothing wrong with Hagar, that is what I usually fit. The usual installation is a dual RCD CU as RCBOs are about 20. If the electrician swapped the old fusebox and the Hagar is not an additional CU then I suspect that all the circuits are now RCD protected.

The shower can share an RCD with other circuits (it needs it's own MCB of course).

Replacement of a damaged cable is allowed. eg hang a picture and the nail goes bang.
Looks to me like I have two choices, take your

Or get the electrician to issue you with a "PIR" later on after you have done the work and any other electrical work you have done. I have no problems doing that when people have DIYed a job. I just cannot issue an installation certificate. I get to see both extremes of the diy abilities - from the dangerous to the better than my work.
Cheers
Adam
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