Ring main from shower feed?

[Theumpire]

Is it acceptable to use a redundant shower feed, 40 amp rcd, to feed a new consumer unit to run a small ring main, three dual sockets, a single light and three external lights? Any help or advice appreciated.

 

[Taylortwocities]

Aah, you have fallen in to the trap.

That RCD has contacts that are rated at 40amps, but the RCD itself does not provide any over=current protection.

What is the value of the fuse/MCB that feeds that RCD?

 

[JohnW2]

Is it acceptable to use a redundant shower feed, 40 amp rcd, to feed a new consumer unit to run a small ring main, three dual sockets, a single light and three external lights? Any help or advice appreciated.

[I suspect you mean that there is a 40A MCB, as well, possibly, as an RCD?] If so, to do as you describe, with a CU and appropriate MCBs on the end of the cable, that's fine - the old shower cable has effectively become a distribution circuit or 'sub-main'.

People sometimes hang a ring off the end of an old shower or cooker cable, without an intervening CU for the final circuits (known as a 'lollipop' circuit). I inherited such a set-up in my cellar, and lived with it for a good few years. Provided all the cables are suitable for the MCB's/fuses involved, I can't really see anything really electrically wrong with it - but it is sometimes frowned upon, not the least because it produces some problems (or confusions!) with testing.

Some would argue that it's not really worth having a ring for just 3 sockets, instead favouring a 'radial' circuit.

You're new sockets, and maybe the lighting circuits (if cables are 'concealed') will need RCD protection - which it sounds as if the circuit probably already has.

Kind Regards, John

 

[AndyPRK]

It would be interesting to know the MCB value.
But a radial would sound more suitable and then a 3A fused spur for your lights

 

[ericmark]

Rather than a full blown consumer unit you can use fused connection units (FCU) and as well as stand alone you can also get them to fit in a grid switch which means a far neater arrangement and still fused down for lights etc.

As already said radial rather than ring may be better for so few sockets.

 

[JohnW2]

Rather than a full blown consumer unit you can use fused connection units (FCU) and as well as stand alone you can also get them to fit in a grid switch which means a far neater arrangement and still fused down for lights etc.

All true, in principle. However, if the OP wanted the possibility of more than 13A total from his sockets, he would probably need multiple FCUs (although some would argue that he might not need FCUs at all!), just for the socket circuit, plus at least one other for the lights (interior and exterior) - which I'm not sure would be 'much neater' than a mini CU. Also, if the feeding shower cable is 6mm² (or perhaps even 10mm²) one might struggle with it in an FCU and certainly with grid modules. I personally suspect that a mini-CU (as proposed by OP) might be the easiest/best solution ... but there are obviously many ways to skin a cat!

Kind Regards, John