Rewiring Domestic Premises - 17th edition compliance

My father in law, who was an electrical engineer for many years (now retired) is in the process of rewiring his sons house (1950s).

Does the consumer box has to have an RCB for all lighting circuits? He has been calling around and been getting differing answers. anyone here know a definitive answer to this? The consumer box has two lighting circuits via two MCBs but has got no RCB protection. The ring main sockets are all RCB protected.

Any advice would be very welcome.
Thanks.

Lighting circuits don't specifically have to be RCD'd (apart from in a bathroom), however, I believe any cabling that is buried in a wall less than 50mm from the surface must be RCD'd (unless in earthed metal conduit) - this means that in most houses they need to be, given how the cabling is normally run to switches.

The 17th edition also effectively specifies that you can't just have one RCD supplying lots of different circuits, so that e.g. tripping it from a socket doesn't cause your lights to go out as well - the normal solution is to get a dual RCD board, or use RCBOs for each circuit.

Also note that this work is almost certainly covered by Part P of the building regs (see the wiki for detail), so his son should have notified the LABC before any work started...

Hi,
17th edition wiring regs are the standard which your rewire will have to be carried out to. There are exclusions which you do not require rcd on all circuits but unless you meet the criteria you will need rcd's protecting all circuits worked on. Ask Father Christmas for the On Site Guide, this book is invaluable for this project and as he has been out of the loop for a while then I would strongly advise reading it.
Unless the wiring is more than 50mm buried in a wall, is protected by an earthed metallic mechanical protection or likely to be used by skilled persons are some of the restrictions from the top of my head, then rcd's are required. If he is just rewiring the lighting circuits he can fit rcbo's to each circuit worked on but these are sometimes awkward to fit in an old consumer unit, but you can buy a dual rcd consumer unit for less than 2 of these devices. Hope this helps.

1) If the house is in England or Wales then rewiring it is notifiable under The Building Regulations.

See here: //www.diynot.com/wiki/electrics:part-p

2) Ditto it has to comply with P1, and the usual way in this country to show compliance with that is to comply with the IEE Wiring Regulations.

3) This is a simplification, there are some exceptions to some of them, but it's a good starting point - the Wiring Regulations basically require all of the following to have RCD protection:
- Socket circuits
- Bathroom circuits
- Any circuit with cables concealed in walls or partitions which are not mechanically protected or buried more than 50mm deep.

4) If your FIL is an engineer, he ought to appreciate his duty to do the following:
- comply with the law
- comply with any other applicable regulations, so if he chooses to work to BS 7671 he should obtain a copy of it, and practical guides such as the On-Site Guide and the Electrician's Guide to the Building Regulations
- ensure that he is competent to carry out the work.

Guys, just wanted to say many thanks for your detailed replies. He is going to take the box back and replace it with the one he needs. Thanks again!

p.s Npower engineer told him otherwise which so its a bit of a worry eh?

The nPower engineer is probably not hugely familiar with the wiring regs - they only work on the leccy board side of the meter, at which point entirely different rules etc apply. Also, it is only the 17th edition (this years) that has become much more strict on what needs RCDing - under the 16th you wouldn't have needed to...