Wall lights on a spur from ring circuit

[JohnW2]

What would make you think its a radial circuit? My understanding is that radial circuits are rare in the UK.

Probably not as rare as you might think - and that is increasingly the case. The arguments in favour of ring circuits are really pretty marginal/weak (and such circuits are almost unknown outside of the UK and some historically 'anglophile' countries).

A while back on another socket in the same circuit I measured 220V on both cables with the wires disconnected, so I took this as confirmation that it was a ring circuit.

That would be a ring circuit, then - but you hadn't told us that!

Kind Regards, John

 

[Kaymo]

Probably not as rare as you might think - and that is increasingly the case. The arguments in favour of ring circuits are really pretty marginal/weak (and such circuits are almost unknown outside of the UK and some historically 'anglophile' countries).

I had read that radial circuits were rare in the UK (although that info might be out of date), but I was aware that it was the norm in other countries. I lived in Ireland and the USA for a 10 year period, and had some electrical work on machinery in industry, but I hadn't really done any work on domestic circuits before leaving the UK, so the first time I had to do anything in the house after getting back here I was pretty confused by the ring circuit, and didn't understand why I had two live wires. Fortunately, even once the breaker is off, I have an ingrained habit of checking the voltage, then shorting to earth, before I touch any wire, so I didn't presume that because one cable was live the other must safe!

I don't know much about the pro's and con's of ring and radial, but since my first surprise a few years back I am aware that a ring is likely in UK homes. From my own experience I can see how someone from another country, who is otherwise reasonably competent with electricity could be caught out by a ring circuit, as its not what you would expect.

That would be a ring circuit, then - but you hadn't told us that!

I did, in the first sentence of of my first post.

a switch which is part of the the ring circuit

 

[EFLImpudence]

I had read that radial circuits were rare in the UK

I know you are referring to your socket circuit, but radials are of course used for everything else in the UK.

 

[JohnD]

I had read that radial circuits were rare in the UK

not exactly rare.

a great many houses have an immersion heater, or an electric cooker, or an electric shower, or some storage heaters. Some have a shed circuit, or a dedicated freezer circuit. Some have a dedicated doorbell circuit or alarm circuit.

 

[Kaymo]

I know you are referring to your socket circuit, but radials are of course used for everything else in the UK.

not exactly rare.

a great many houses have an immersion heater, or an electric cooker, or an electric shower, or some storage heaters. Some have a shed circuit, or a dedicated freezer circuit. Some have a dedicated doorbell circuit or alarm circuit.

Accepted. I should have said rare for domestic mains socket circuits.

This is what I meant by ring circuits seeming strange if you are not familiar with them. Unless it was 3 phase, pretty much everything I worked on in industry, and on cars even, was what in a UK house you might refer to as a radial circuit. I had worked on those things for years, and had replaced a few domestic appliances like shower units and cookers etc, before I ever had cause to do anything with a plug socket, so my dangerous presumption the very first time I came across a ring circuit was that one of the cables on the supply side was taking power to the next socket.

 

[JohnW2]

I had read that radial circuits were rare in the UK (although that info might be out of date), but I was aware that it was the norm in other countries.

|Prior to WWII, sockets circuits were all radial in the UK. After the war, the concept of ring circuits was introduced (allegedly because of a belief that it would reduce requirements for copper, at a time when limited amounts were available) and then became more-or-less the norm for new sockets circuits for a number of decades.

I don't know much about the pro's and con's of ring and radial, but since my first surprise a few years back I am aware that a ring is likely in UK homes.

I'm sure that they are still much more common than radials (for sockets circuits) but, as I said, that seems to be changing.

There really are very few 'pros' of the ring final circuit. Whether or not it requires 'less copper' depends on the physical location of the sockets - if they are arranged ('radially') in roughly a straight line radiating from the CU, then a ring final will require more copper than the corresponding radial circuit. The main theoretical advantage is that it allows a cable rated at as low as 20A to be used in a 32A circuit but, in practice, that is not often a very significant advantage. If, as is commonly the case, 2.5mm² cable is installed by 'Method C' it has a CCC of 27A (and hence a 25A 2.5mm² radial is OK), which is not much less than 32A. About the only other 'pro' is that it provided 'CPC redundancy', which might be perceived as a safety advantage.

As for 'cons', if one has socket(s) close to one end of a ring, it is theoretically possible to overload the cable of the 'short' leg of the ring - and designers are meant to take steps to render this "unlikely for long periods". The fact that there is "L & N redundancy" is also really a 'con', since the ring can break, hence theoretically possibly overloading some of the cable, without the user being aware of any problem.

As EFLI has pointed out, rings are only used for sockets circuits, even in the UK, everything else (e.g. cookers, showers, immersions, virtually all lighting etc. etc.) are supplied by radial circuits.

I did, in the first sentence of of my first post.

Not really. You said it was a ring circuit, but it was not until post #16 that you told us that you had previously measured the voltage on both cables disconnected from a socket on the same circuit Without that information, your 'two cables' socket could have been on a radial circuit!

Kind Regards, John

 

[Kaymo]

Not really. You said it was a ring circuit, but it was not until post #16 that you told us that you had previously measured the voltage on both cables disconnected from a socket on the same circuit Without that information, your 'two cables' socket could have been on a radial circuit!

I still think its a bit of a stretch to say that I hadn't told anyone it was a ring circuit, it was in my first post. I was confident that it was a ring circuit, and I wasn't looking for clarification on that point, I was asking about the spur of to the wall light. The only reason I mentioned the voltage on both cables was in answer to someone asking me, and I totally understand why someone would want to check this, but I did state from the outset that it was a ring circuit.

Anyway, I don't want to argue about the small stuff when I have had good and helpful advice from everyone, and I appreciate the extra info around ring versus radial.

Thanks again all.

 

[JohnW2]

I still think its a bit of a stretch to say that I hadn't told anyone it was a ring circuit, it was in my first post.

You may have misunderstood, because I never intended to suggest otherwise. I was saying that you hadn't initially told us that ...

... A while back on another socket in the same circuit I measured 220V on both cables with the wires disconnected ...

... which clearly is very relevant information.

I was confident that it was a ring circuit ...

.. and, as we now know, you had every right to be confident, because you had undertaken those measurements. However, since we didn't know that at the time, there was no way that we could be confident that it was a ring circuit.

We have many people coming here who (incorrectly) assume that 'two cables at a socket' necessarily means it is a ring circuit - even though, as has been said, nearly all sockets on a radial circuit also have two cables. We therefore were not 'getting at you' but just wanted to be sure that you were not making that mistake and concluding that it was a ring solely because a socket had two cables. You subsequently reassured us about that - but, since very few people 'assuming' that a circuit is a ring will have undertaken such measurements, we had no particular reason to think that you would have done.

Kind Regards, John