Unfused Spurs from a Ring Circuit

yes. You may supply an unlimited no of sockets through a fused spur.
However I suspect most sparks would rather open the ring and extend that, as the 'small loads only' assumption may not be met in future.

The 'top right' on the diagram below.

edit  PS a triple socket has a single 13A fuse built in, covering all 3 sockets. so is an example of what you are considering anyway, just with the shortest possible length between sockets and  the fuse.

Mike.

Thank you for your reply. I understand your point about future demand of the sockets. Extending the ring might ne disruptive. Should I assume that electricians would be wary of implementing such an arrangement as I have described.

Re your diagram, thanks for that. It's slightly different to what I had envisaged because the FCU is connected in the ring and not at the end of an unfused spur cable.

Thanks for the MK pic. I'd seen those. If this was connected at the end of the unfused spur cable would the onboard fuse effectively act as the "FCU"

Yup. 'wary' covers it !!

you can put the triple socket at the end of an unfused spur, because the total current is limited by the fuse, the end at which the limiting occurs is not so important, so long as if there were ever  damage to the cable supplying it can cleanly blow the upstream protection (rather than just catch light and blow nothing. )

In this case upstream is the breaker at the consumer unit. So a very thin cable with a 1A fuse on the end of it from a 30A supply  would probably not be OK, but a 2.5mm2 with a 13A fuse at the load end, supplied from  30 (or even a 40A) breaker would be.

Sometimes you also see unfused spurs of higher loading but wired to the ring in 4mm2, but that is not a standard arrangement, and is not good, if that load is very near one end of the ring, so the clockwise anti-clockwise split is uneven (which of course depends on the relative lengths==resistances of the 2 possible current paths)

Mike, 

Horace Charles said:

Extending the ring might ne disruptive.

You are going to have to break into it somewhere, unless you already have a spur.

If you are going to have surface-mounted sockets, what will supply them please?

Thanks Chris and Mike for your replies. Here is a bit more information regarding the things I will be asking a Part P electrican to look at.

Upgrading the Consumer Unit to an up to date model with RCBO protection. The current CU is an old Wylex fitted with cartridge fuses, so the ring circuit currently has a 30 amp fuse.

Then to look at the options for additional sockets on the wall of a long lounge.

To minimise disruption and avoid making good and redecorating I thought of the surface mounted socket possiblity.

I have drawn the attached diagram. Ignore the reference to RCD FCU. RCD protection will be supplied from the new CU.

For minimum disruption I envisaged close connection to the ring at the existing socket with the very short spur cable routed behind the FCU surface box into the side of the existing socket backbox.

The diagram is just an idea and I thought would allow more surface sockets to be positioned along the wall. Perhaps the electrician will have a better idea.

Sorry I cant see the option to attach my diagram 

Upgrading the CU seems like a very good idea.

To add a diagram, just drag and drop into the text box.

"assumed to be on the ring circuit" - that is definitely worth checking before you go too far down that route - it's surprising what lengths some people went to to save a couple of metres of cable - I've seen many a house where the developers ran a ring around the first floor floor void and every socket downstairs was on a spur dropped down from it. Even seeing two cables behind a socket is no guarantee - older regs used to allow two singles on a spur, and they're often then "upgraded" to doubles without proper consideration, or just done by people who never understood the rules in the first place.

   - Andy.

Thanks Andy for your reply. In the absence of easy visual access to check that I'm hoping the electrician will be able to determine that by resistance tests? Its a bit of a minefield ! Maybe Chris's tongue in cheek trailing socket approach is starting to look appealinng

Splendid! That makes sense.

I can see the point about decor and making good. It might still be relatively easy to extend the ring. Something has to go next to the existing sockets, but there could be another socket, or even a blanking plate. If there are a few inches of slack in one or other side of the ring, or room in the backbox so that (maintenance-free) terminal blocks can be used, extending the ring should not be a problem. Granted, it uses more cable, but two lengths of 2.5 mm² will sit comfortably side by side in mini-trunking.

That is something for your sparks to find out.

AJJewsbury said:

"assumed to be on the ring circuit"

My thoughts entirely, but it seems unlikely to be a radial. Let's not get too technical and confuse Horace. :-)

I hope, Horace, that you now feel more clear about the way ahead. If not, feel free to ask.

Thanks Chris and all other respondents

My conclusion is that although technically permissible within the regulations, feeding multiple sockets in the way I envisaged would be considered "poor practice" by electricians because of the potential consequences of the plugging in of high current items (FCU fuse blowing).

So I will be discussing with the electrician, the option of extending the ring at the existing flush socket, to "break out" into new surface sockets all connected in the ring.

Some disruption to the wall decor might be unavoidable, but it has to be done right.

Thanks again to all for your feedack

Thanks Chris and all other respondents

My conclusion is that although technically permissible within the regulations, feeding multiple sockets in the way I envisaged would be considered "poor practice" by electricians because of the potential consequences of the plugging in of high current items (FCU fuse blowing).

So I will be discussing with the electrician, the option of extending the ring at the existing flush socket, to "break out" into new surface sockets all connected in the ring.

Some disruption to the wall decor might be unavoidable, but it has to be done right.

Thanks again to all for your feedack