Radial vs Ring

[Barney12]

I've been enjoying* the recent threads on CU's ecetera. 

Im really likening the idea of radial circuits. In fact the last few conversions we've done have all had cbus lighting which is entirely radial. 

So other than the slight negative of adtional wiring (bit it doesn't seem a lot to me) are there any disadvantages?

Are there occasions where a good old ring is still better? 

In short in the perfect world which is better; ring or radial? 

 

*Well mostly. Please note as the OP of this thread I polightly request that the word "lethal" is excluded from all replies  

Edited January 24, 2017 by Barney12

[PeterW]

.... and can someone draw a simple picture of how radial is done...?? Junction boxes..? Wago's..?

 

And why is it better..?? Or worse..?? Limitations..??

[ProDave]

The wiring is the same, you loop from socket to socket, no need for junction boxes.

 

Think of a ring final. Remove the link between the two furthest sockets and then connect the two ends in the CU into their own mcb's.

 

The disadvantage of radial sockets is in general you will need twice as many of them so more mcb's and a bigger consumer unit.  No problem in a new build but in a lot of existing houses there is simply no room to fit a bigger CU

 

Converting a ring to two radials is often a handy trick to have when you find a damaged circuit leg and the distruption to the property needed to fix it, can make it a better option to scrap the damaged section and convert it to two radials.
 

[Jeremy Harris]

36 minutes ago, Barney12 said:

I've been enjoying* the recent threads on CU's ecetera. 

Im really likening the idea of radial circuits. In fact the last few conversions we've done have all had cbus lighting which is entirely radial. 

So other than the slight negative of adtional wiring (bit it doesn't seem a lot to me) are there any disadvantages?

Are there occasions where a good old ring is still better? 

In short in the perfect world which is better; ring or radial? 

 

*Well mostly. Please note as the OP of this thread I polightly request that the word "lethal" is excluded from all replies  

 

FWIW, I much prefer the idea of going back to radial wiring.  It was the standard in the UK for years, I think until the price of copper and post-war belt-tightening, caused the switch to ring circuits. 

 

I have a personal view (and please bear in mind this is just my personal view) that radial wiring is more logical and can be safer.   It's normal in many other countries to use radial wiring, and I have a feeling that the UK is in the minority in sticking to ring circuits.  I remember fixing a problem in a house in the US (well, helping the owner find and fix a fault) and that house was radially wired, but interestingly with aluminium cable.  Needless to say using aluminium cable (or, to be correct in this context, "aluminum" cable) causes corrosion problems at connections, so normal practice there with this stuff is to squirt some anti-corrosion stuff on all connections.  The fault we located was caused by a corroded connection, which is why I remember it.

 

[Barney12]

1 minute ago, JSHarris said:

I have a personal view (and please bear in mind this is just my personal view) that radial wiring is more logical and can be safer. 

 

 

That is exactly my thought.

[joe90]

Am I right in thinking that a radial system has a fuse ( or whatever) per socket on one piece of wire from the CU? As that surely would be a lot of fuses ( or whatever) and cable.

Edited January 24, 2017 by joe90
Edit

[Jeremy Harris]

Just now, joe90 said:

Am I right in thinking that a radial system has a fuse ( or whatever) per socket on one piece of wire from the CU? As that surely would be a lot of fuses ( or whatever) and cable.

 

Not under UK regs, as far as I know (but I've not had a chance to go through amendment 3 yet, but I don't think that's changed things from the copy of the 17th Ed I've got). 

 

It's fine to have multiple outlets on the same radial, as long as the cable is sized correctly for the load, taking into account diversity, cables passing through insulation, max allowable voltage drop and all the usual stuff that applies to cable sizing.  You can have more than one 13 A outlet, for example, on a single radial, using normal 2.5mm² T&E.  The maximum number would depend on the factors already mentioned. 

 

One thing to look out for is the size of the CU, and the space it will take up, bearing in mind that you're going to have at least double the number of MCBs or RCBOs in it.

Another is cable runs, as you can, in some layouts, have quite a lot of cables going in roughly the same direction.  Neither of these are show stoppers, in my view, and I was tempted to spec our build as radial, but I was pushed for space on the wall in the services area, and a bigger CU would have been a bit of a problem, especially when allowing for all the cables that come up on that same wall.

[joe90]

Thanks Jeremy, a very clear answer. As per my comment on another thread about not understanding the finer details of this stuff and earthing types ( and preferring woodwork ?) I think I will leave the planning to my builders electrician as he will have to sign it off anyway, but it's good to know. Personally I will have no restrictions on size for the C.U. or cable runs.

[Steptoe]

2 hours ago, JSHarris said:

 

FWIW, I much prefer the idea of going back to radial wiring.  It was the standard in the UK for years, I think until the price of copper and post-war belt-tightening, caused the switch to ring circuits. 

 

I have a personal view (and please bear in mind this is just my personal view) that radial wiring is more logical and can be safer.   It's normal in many other countries to use radial wiring, and I have a feeling that the UK is in the minority in sticking to ring circuits.  I remember fixing a problem in a house in the US (well, helping the owner find and fix a fault) and that house was radially wired, but interestingly with aluminium cable.  Needless to say using aluminium cable (or, to be correct in this context, "aluminum" cable) causes corrosion problems at connections, so normal practice there with this stuff is to squirt some anti-corrosion stuff on all connections.  The fault we located was caused by a corroded connection, which is why I remember it.

 

 

Im fairly sure I said similar yesterday,

anyway,

I digress,

 

RADIAL

PROS

quicker to install

less cable

safer

less inconvenience under fault

easier to segregate circuits

a cable that is actually protected by an OCPD that is of a suitable size

 

CONS

requires more ways in the CU

 

RING

PROS

higher loading permitted for same size cable

thats about it really

 

CONS

unsafe - a cable that can ideally carry 27A is usually protected by a 32A MCB relying on the balance of current flow to avoid mishaps, this is normally fine until a fault develops or the cable gets cut/split/damaged etc

more cable

more install time

more inconvenience under fault conditions

 

 

thats the main considerations

[Crofter]

My tiny wee house is planned to have a single ring circuit plus of course the kitchen stuff, shower, etc.

Intruiged now about radial circuits- I will of course get proper advice on this but talking very roughly, could I put the bedroom and lounge on the same radial (total of six double sockets) and then the two or three kitchen sockets on their own radial (that's where any high current stuff like kettles would be going). Just looking for ballpark yes /no. Assuming 2.5mm T&E, running in a service void, not within insulation.

[Onoff]

In a nutshell, laymans terms if you will:

 

For final circuits, the ones where you "plug things into", or have fused connection units etc:

 

You can have:

 

An (A1) ring circuit on a 30/32A overcurrent protective device, "opd" run in 2.5mm serving a floor area of 100 square metres max.

 

An (A2) radial again off a 30/32A opd run in 4mm serving a floor area of 75 square metres max.

 

An (A3) radial off a 20A opd run in 2.5mm serving a floor area of 50 square metres max.

 

You need to try and ensure your loads are spread between the legs of the ring btw.

 

All in the On Site Guide to the regs. In the actual regs there's even excellent, pretty pictures showing all these in the Appendices. Sorry, but I'm not about to go scanning pages from my books.

 

Be careful with 4mm radials as some sockets have such small L/N/E terminals you'll struggle to get the wires in. Let's face it some are so dire you won't get 3 x 2.5mm in!

 

And you can go "off piste". You can sometimes for example reutilise an old cooker connection point and come off of that with a ring! Colloquially known as a lolipop circuit. All perfectly legit if you can justify the design.

 

But.....with everything "you" need to consider a multitude of things; the installation method for the cable, the ambient temperature, opd characteristics (Type B, C, D )...grouping list goes on and on. For instance if a cable is covered by thermal insulation for more than 500mm the current carrying capacity of that cable should, as a rule be HALVED. It could mean you need to go up a cable size. This issue often manifests when high current cables such as for showers get insulated over and they basically melt!

 

It's a whole new lot of esoteric terms for most. (Just like when I couldn't figure what a "PIR" had to do with insulation! )

 

It's why people go to college etc for their respective trades.

 

Of course, get it wrong and...it's the L word!