No offence intended atall Rob, so hopefully none taken your end.
But are you actually doing a pucka PIR, or doing a CU change, or doing a quick assessment ahead of a proposed install job. Your various comments leave me a little confused...
Firstly, altho you mention you do have a 2391 (& they don`t give those away) you haven`t instilled too much confidence with some of your remarks (e.g. Regs & minefield) No-one passes a Periodic exam without knowing BS7671 at least fairly well. We all have holes to our knowledge & i`ll gladly help you fill some of yours (& hopefully my own at the same time)
Likewise, if you`re Part P reg`d you`ll surely be familiar with most of the pertinent regs. If not, be aware what you`re gonna do will be notifiable. And as it was you who mentioned legalities a bit ago...
Lecture mode off
So, making the assumption that this work is for a PartyPee assessment
we`ll all stick our noses in & make an obsevation or two...
Q. How sure are you that`s not an ELCB mate? Kind a looooks like one from the pic
Q. How sure are you that it`s a TN. The tails coming in plus that Volt op` RCB has me wondering see
Q. Have you actually seen the service head? The above will quickly be answered...
If, as you say it is TN then i`d suggest you get the DNO in to sort out those tails tother side of that isolator before you consider getting assessed on this job. Obviously you`ll do the rest with the Cu change.
Talking of which, forget the idea of the front end RCD - very non comp mate. No discrimination atall. You should already know that. If you get a true 17th board you won`t even need it. And if it does turn out to be a TT you can do without it too if you can do what table 41.1 states.
Anyhowsaround, i`ll leave it at that for fear of lecturing again
Sorry if it`s sounded more blah, blah than bah, bah but i`ve had me coat dyed pink today
Best regards, Al