Radial / Ring Circuit

[Adiatu olayinka]

What is the difference between the two

[ban-all-sheds]

A ring circuit forms a complete ring running from the CU, to all the sockets and back to the CU, like this:



A radial does not



But you have already seen those diagrams, and they can't be much clearer. If you can't see the difference between them then I suggest you stop wondering about it, and don't plan to do anything where it matters to you what the difference is.

__________________
I mustn't warn people that the "experts" on the plumbing forum can't be trusted to tell the truth.

[securespark]

Ban

Is it just me mate, or have you developed "attitude" since I came back from hols?

[AdamW]

He don't take no shed from nobody no-more!

[ban-all-sheds]

securespark wrote:

Ban Is it just me mate, or have you developed "attitude" since I came back from hols?

Me - no, same old easy-going self.

It's just that Adiatu went to the "How to" page for converting a radial to a ring, where he would have seen those two diagrams, and read this:

The principle of the radial circuit, is that the mains cable leaves the consumer unit and passes through each socket until it reaches and ends at the last socket. Alternatively, on a ring circuit the mains cable leaves the consumer unit passes through every socket and then returns to the consumer unit..

You have to worry about somebody interested in "how to" when he can read that, look at those two diagrams, and then still have to post here "What is the difference between the two?".

__________________
I mustn't warn people that the "experts" on the plumbing forum can't be trusted to tell the truth.

[shyann]

i think he ment in what circomstances would you use them and why

[ban-all-sheds]

I don't think that after 4 years it matters why.

__________________
I mustn't warn people that the "experts" on the plumbing forum can't be trusted to tell the truth.

[ericmark]

Except with MK sockets which have larger than required holes to comply with standard it is very hard to get 2 x 6mm cables in them. As a result in the main a radial is supplied from a smaller MCB than with a ring main.
Normally 32A for ring main and 20A for radial.

With the ring faults and bad wiring can result in overload, this is less likely with a 2.5mm radial but where high power is required for example a kitchen the single radial is more likely to trip due to overload.

With the introduction of RCD protection on all sockets the ring main serving a large area is more likely to trip than a number of radials serving the same area where RCBO's are used.

So to feed each room with a radial except kitchen where a ring would be used and have them all on RCBO's would reduce the likely tripping of the RCD and when it did trip reduce the area affected.

But this does not take into account cost and with a 3 bedroom house using normally 3 ring mains this would be replaced with 1 ring and 5 to 8 radials so will require 2 to 5 extra RCBO's and extra cable. And with twin RCD protection would hardly have any advantage.

Of course 6mm radials could be used but this would fill the holes in even MK sockets so to expand latter would be harder and you still have the problem of people using wrong size cable.

Some people seem to think 4mm cable can be used with 32A radials but unless surface this is unlikely which means there is another problem where to comply with current carrying capacity you may get a mixture of cable sizes which since they would have same current carrying capacity would in theory be permitted but in practice it is asking for mistakes to be made.

The same problems exist where Ali-tube or mineral cable is used and because this cable can run hotter smaller csa is permitted but OK for a correctly planned installation but where DIY is likely to be carried out in the future I think it is asking for DIY mistakes to be made.

We would normally use method 100 which would give twin and earth 2.5mm = 21A, 4mm = 27A and 6mm = 34A but when you start on specials then Ali-tube cable clipped direct at 2.5mm is rated at 33A so in an industrial premises where all cables are exposed you could run a radial in 2.5mm protected by a 32A device and the regulations cover all not just domestic so it has to include what may only be used in industry.

In a house I would say ring = 32A and radial = 20A and all socket wiring in 2.5mm or in future mistakes are likely.

Does this answer question?

[shyann]

yes thank you