Ring main or Radial for sockets in extension?

[uptown47]

Hi all,
I'm not a qualified sparky but I'm a very competent DIY'er (with lots of electrical experience in industrial applications - three phase, low voltage stuff etc).

We've got an extension built and I just want to run 4 sockets and some lights into it. Everything is easily accessible because there's no plasterboard or anything yet.

The kitchen is on it's own small consumer unit as we had the kitchen re-done a few years ago and the main board was quite full so the sparky (at the time) put in a small board to just feed the kitchen (it only has Cooker, Sockets, Underfloor heating on it).

As it's the kitchen that's being extended I thought I would just break into the Sockets ring and then extend it around the extension and back. However, looking at the small consumer unit there's only one Live wire in the CB for the kitchen so the sockets must be run as a radial circuit.

I started Googling this and stumbled across a YouTube video of a guy explaining that Radial ccts are better than Ring (even for sockets)??

Is this the new way of doing things? The YouTube guy reckoned that the problem with Ring ccts are then if one leg has a break in the cable the whole ring still works but there's a danger of overloading (as all the current is going down one leg and not shared between the legs). However, a radial is safer as, if there was a break, part of the radial would stop working and so would alert you to the break??

I just wanted to get a second opinion on this before I tackle this work and gauge what the general consensus is?

Thanks for your help.

 

[EFLImpudence]

No, not new. Only Britain and British places use the British ring circuit - no one else does.

Nowadays it depends on the location.
If the circuit IS in a rough ring, then you could install one - although two radials would probably be better.

There is no point having a ring if the cables run out and back in the same place.

 

[flameport]

All circuits are radials, except for the one specific example of a ring which was designed in the 1940s with the intent that one would be used for the whole house, which was a saving in materials compared to previous wiring methods.

If you are installing one for the whole house, or even possibly one for a room with a high load in it such as a kitchen, a ring may be a valid option. Even then, it's certainly not the only option.

For a room with 4 sockets, it's entirely pointless.

Is this the new way of doing things?

Radial circuits are not new, they have existed for as long as electrical wiring has. Radial circuits are the standard method of wiring and have been for well over 100 years.

 

[Keithmac]

Just out of interest how do you calculate what wire thickness you would need for a radial, do you assume ever socket has a 13 Amp load? (Which will probably never happen).

Could you run it in oversized wire just for belt an braces?.

For me the only advantage of a ring is if an earth wire had poor connection, our radial light circuit had a problem at the first ceiling rose (which was poorly installed) but that cut earth to all our fancy metal clad light switches which isn't the best..

 

[AndyPRK]

Light circuits are radial.

what size fuse /Mcb does the kitchen SOCKETS ?

As you say only 1 wire leaves the Mcb.

If the protective device is between
15-20A use 2.5mm cable
30-32A use 4mm or 6mm

Wire new sockets As a radial.
Take a spur from the existing socket

 

[flameport]

Could you run it in oversized wire just for belt an braces?.

Yes, but to achieve what?

A circuit is designed so that the protective device (circuit breaker, fuse or whatever) is rated lower than the cable, which ensures that the cable can't be overloaded and damaged.

Such as a 20A radial circuit using 2.5mm² cable, which is rated to about 26A if on the surface or concealed in plaster walls.
That could be installed using larger cable, but it would just be a waste of money, the circuit is still only 20A.

Circuits are designed for a particular load - in the case of socket outlets some assumptions have to be made as to the likely use of them, which depends on the location that they are installed.
Sockets in a kitchen being entirely different to those in a bedroom.

 

[sparkwright]

You need to determine the size of the cable of the socket circuit at the consumer unit.

It would also be interesting to check the cable size at the existing sockets too. (It may be different.)

And, as said, we need to know the size of the fuse or circuit breaker.

 

[securespark]

One reason to use a bigger size of cable could be if the cables are run in insulation.

 

[sparkwright]

One reason to use a bigger size of cable could be if the cables are run in insulation.

Another reason would be if one larger cable from the consumer unit goes to feed a smaller cables in the form of a ring - a lollipop circuit.

Would be worth evaluating what this kitchen socket circuit is before trying to add to it.

 

[AndyPRK]

If it was a Lolly, they would have used a 32A, otherwise it would have been pointless to do so

 

[sparkwright]

If it was a Lolly, they would have used a 32A, otherwise it would have been pointless to do so

I know, but we don't know what fuse or MCB has been used yet.

 

[uptown47]

I know, but we don't know what fuse or MCB has been used yet.

Thanks for all the replies and information.

The current "Sockets" cct for the kitchen is running in 2.5mm T+E from a 20A breaker. The extension itself isn't going to be using much. It'll have the Christmas tree plugged in at Christmas and maybe a standard lamp / phone charger etc. Just bits and bobs of stuff. So I'm inclined to just extend the circuit but first I'm going to just map out exactly what sockets he put on that circuit.

Part of our extension is a 'utility' room that will have a washing machine / tumble dryer so I'll probably put them on their own radial circuit with a switched fused spur for each of those sockets.

Thanks for all the great advice.

 

[winston1]

Part of our extension is a 'utility' room that will have a washing machine / tumble dryer so I'll probably put them on their own radial circuit with a switched fused spur for each of those sockets.

Thanks for all the great advice.

Absolutely pointless to have a switched fused spurs. The appliance plugs will have fuses in them.

 

[uptown47]

Thanks. That was how the original electrician did it so I was just going to move those sockets but replicate the method.

 

[bernardgreen]

Absolutely pointless to have a switched fused spurs.

Consider if the appliance develops a fault that causes the RCD to trip then access to a means to isolate the appliance is necessary to allow the RCD to be reset. ( Isolate means Live and Neutral disconnected ). If the plug is easy to access then pulling the plug achieves quick and easy isolation.

If the socket is behind the appliance and the appliance is difficult to move then a remote and accessible double pole isolator will enable the RCD to be reset without having to move the appliance.