changing CU

One point worth checking is that you have enough room to install your chosen CU - the larger ones are surprisingly wide, and that can be a problem when working in a cupboard etc.

I'd recommend having some gaffer tape handy. Mine when pulled out leaves a big (like two inch by one inch) inviting hole with big bare contacts in in. Far too much possibility of getting a stray finger, tool, or the other end of a wire into it by mistake - tape it over while you're working.

Pete

Or remove the main fuse from carrier (stick it in your pocket etc) and replace the empty carrier?

One other point. All of the existing wiring is in red and black. When fitting a new CU, where should I change to the new colours ? If I change any wiring before the CU, is it OK to have a mix of red/black and blue/brown here ? Thanks, Simon.

sm_jamieson coughed up some electrons that declared:

Yes it's OK, but you must apply one of these to the outside:

Cheers

Tim

OK, trying to get the number of circuits down. Nice to have separate fixed appliance radial in kitchen, but takes up another slot. So ... In kitchen some fixed appliances and various sockets. If fixed appliances off a 32A ring (e.g. 32A MCB) plus kettle etc., could get a bit close to limits. Is it permitted to have a higher powered ring for the kitchen, using

sm_jamieson coughed up some electrons that declared:

Not to my knowledge as I believe a ring final circuit is a special case final circuit defined as 32A max, with cables to be designed for 20A or greater.

You can have radial circuits too, but IIRC the BS for 13A sockets defines the socket terminals as capable of taking:

So it's often not easy to get to 32A let alone beyond, many radials operate at 20A, maybe 25A.

HTH

Tim

You can normally ignore things like kettles in domestic loading estimates since they are such short term loads.

Not that I am aware of. You could of course have more than one if you needed.

I've occasionally wondered what practical problem this is supposed to prevent in a domestic setting. I understand that the colours for three-phase have changed in an undesirable way (neutral / phase swap, is it?) but there's no such confusion in a single-phase system. Black and blue are both always neutral, red and brown are both always live. Tradesmen and DIYers are going to be aware of the old colours for many decades yet as they show up in existing installations. And even if some new kid in 2080 doesn't know what this red conductor is that he's found, I doubt the actual wording on that sticker would help anyway.

Still, for 30p I stuck one on - nice to make things look official :-)

Pete

Blue was a phase and is now neutral, Black was neutral and is now a phase.

You may meet some 3&E with a live black conductor on two way light switching.

Indeed.

Until you come to 3-core(+E) cable in lighting circuits, where a blue core could be either neutral or switched line (old colours) and black may be switched line (new colours). Of course these should be marked at terminations with sleeving but you have to allow for the reality that such marking was often not fitted, or tape was used and has fallen off.

The new colours label just alerts you to the fact that mixed colours are in use and that care should be taken. It's a concession compared to the requirements in a 3-phase installation where core marking is required at all junctions between old and new wiring.

Surely care should be taken anyway! Anybody not realising that shouldn't be messing about in a CU...

;-))

Of course in the most common use of three core and earth they are all live.