DIY Doctor

Words of Wisdom

Postby kbrownie » Mon Jun 23, 2008 10:55 pm

My question is as follows;
Removing electric shower 6mm cable on a 45amp fuse.
New regs bathroom on circuit of it's own(RCD)
Bathroom contains whirlpool bath and two seperate lighting equipment (Main Light and LED mood lighting) both ceiling fixed and on two different functional switches.
Is it ethical to use 6mm cable (old shower cable) down fuse reduce cable CSA and place RCD in bathroom cupboard and run a radial circuit to the equipment in the bathroom or place RCBO at cu down fuse at bathroom prior to cable CSA change?
Would LED lighting have any effect on the way circuit should be run and protected?
I ask the question firstly because i'd be interested to know the answer and secondly because of the location of the RCD/RCBO taking 17th eds in to consideration.
Any input welcome!
Rank: Project Manager
Posts: 1995
Joined: Mon Mar 05, 2007 9:36 pm


Simply Build It

Postby ericmark » Tue Jun 24, 2008 8:20 pm

I think in general the 17th Edition is going to cause problems the main consideration is does the Law in the shape of Part P enforce the 17th Editions or does it only refer to 16th Edition i.e. Does it say BS7671 or BS7671:2001 if it says the latter then we may be breaking the Law when following some of the relations of BS7671:2008.
What we must look at is how the courts would be likely to view it. In the main courts look at reasonable behaviour so would to for example demand that a pensioner has a completely new consumer unit fitted in order to have an extra socket to power his freeview box now required as analogue TV is being withdrawn reasonable or would it be considered as extortion and bullying tactics on the part of the electrician even suggesting he needs to spend that much of his pension on providing one socket. We are being forced into the age of extension leads ... aiting.jpg is a good example of how they can also include dangers. So I think we need to use some common sense. If the consumer unit will accept a RCBO then that’s the way to go. If not we must consider the options I would consider fitting a box near to the existing Consumer unit. Because of the price difference between 40 and 100 amp RCD’s feeding supplementary boxes using 25, 40, or 63 amp MCB’s makes some sense. At £23 each putting the RCD after the MCB does make some sense and as each circuit is worked on a RCD can be added one at a time. A small bit of trunking between the two boxes would allow changes as and when required. A Protek 25Amp RCD is about £23 against the £50 for a 100Amp model from same manufacture. At £13 to £15 for a 6 to 10 way box this method would really cut down the expense when looking at one or two items which need upgrading to 17th in the long run as the householder adds more to the system it may cost more than complete consumer change but it will reduce cost now which is what most people look for and it means you have two pole isolation which has to be a plus. I only used Protek as an example as I could find the prices on the net but for the first addition this method would add £36 to the parts cost against £112 for complete new consumer unit and which is more to point inspection and testing only on circuit worked on rather than whole house.
May be I am completely up the creak here and I invite your thoughts.
All best Eric
Last edited by ericmark on Wed Jun 25, 2008 8:38 pm, edited 1 time in total.

Postby kbrownie » Wed Jun 25, 2008 7:20 pm

Complicated one or is it?
The approved document part p of building regs, makes references to BS7671:2001 chapter 13 and the technical rules within BS7671:2001. and also refers to The OSG.
The Electrician Guide again states domestic circuits schedules should comply with BS7671:2001(2004)
At this moment in time I believe a revised version of The Part P Document is ready to be publised as is The Electricians Guide to Part P.
The 17th's OSG was origanally due to be released on May 1st but has been put back to September.
So I assume that The Part P document will be in place to coincide with the birth of the 17th's on July 1st as will The Electricians Guide to Part P.
So if an electrician was currently installing circuits in to a domestic properties to The 17th editions, in what position would he stand in a court of law? (pre July 1st)
But allowance surely must be made, approved documents are there to offer guidance as long as requirements are complied too, but what are the requirements? (now i've confused myself!)
At the end of the day I think that the buck should stop at the requirements of BS7671:2001 and/or 2008 when in place. Why do we need part p? The OSG covers that side does it not? and EAWR is the stat

Rank: Project Manager
Posts: 1995
Joined: Mon Mar 05, 2007 9:36 pm

Postby TheDoctor4 » Wed Jun 25, 2008 9:21 pm

Hi There

Have you checked out the DIY Doctor Projects section:, particularly the projects on "17th Edition Wiring Regulations ( and also the project on "Part P" (

Rank: Project Manager
Posts: 16777215
Joined: Tue Jul 24, 2007 9:12 am
Location: Somerset in the UK in Shepton mallet

Postby ericmark » Wed Jun 25, 2008 10:21 pm

My point is the “Requirements for Electrical Installationsâ€

Postby kbrownie » Thu Jun 26, 2008 7:36 am

Hi again,
I totally agree. Just because an installation needs some minor work doing to it, does not make the rest of the intallation unsafe, because it does not comply to BS7671:2008.
Common sense should prevail and it would be good to think if the electrician could offer the customer a choice, without putting the customers arm up their back and lining their pockets at the same time for work that is not needed.
Not looked at projects on 17th editions yet, but will do.
Rank: Project Manager
Posts: 1995
Joined: Mon Mar 05, 2007 9:36 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!