radial circuits


Postby nollers » Sun Oct 07, 2007 10:17 am

An electrician told me, when calling to quote for some work that needed a qualified person to carry out, that radial circuits are now going to become the norm for domestic wiring,as opposed to ring mains. If this is the case are these circuits able to carry the same or greater loads as a ring? He also said that this was because the ring circuit had been, as he put it, 'abused'. Can anyone throw some light on this?
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Postby sparx » Sun Oct 07, 2007 8:15 pm

Hi nollers,
he has a point, as the only country in the world to use ring circuits it is being increasingly mooted that we move away from the domestic ring circuit.
The 'abuse' he quotes is the number of spurs - off - spurs and open ended rings due to alterations, there are better circuits to use in many circumstances.
when I come to rewire my 35 year old bungalow there will be no rings!
Rings were introduced during a post war copper shortage as it was thought they would cut down on amount off cable runs, but in order to be safe for low power appliances they had to use our fused plugs -unique in the world- and open to wrong fuses etc.
Radials or tree circuits being the option.
Each allowing as many outlets as required within the areas covered:
a 32A ring covering up to 100M2
a 32A radial/tree covering up to 75M2 in 4mm2 cable
a 20A radial/tree covering up to 50M2 in 2.5mm2 cable
the ring can have no more spurs from it than sockets on the ring ie 10 on main ring less than 10 spurs allowed each having only 1 single or double skt on it.
radial/tree no limits to branches off so more flexible therefore I will run a 20A radial to each bedroom, & a 32A radial to each other main room, also much easier to do a rewire as only one room at a time disrupted.
It does result in a larger consumer unit but if wishing to do further work only one area turned off, also easier to find faults, do tests ect,
in my book no-contest regards SPARX
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Postby Evo2463 » Sun Dec 02, 2007 10:46 am

What do building regs and electric regs say about this? Are they both allowed?
Or are you saying now regulations state that you no longer need to do a ring main or ring lighting circuit?
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Postby 333rocky333 » Sun Dec 02, 2007 12:56 pm

At present you can still install rings and there is no regs against it, and no word of change in the 17th regs next year as far as i know.
People will think you crazy (BUT I AGREE WITH SPARX) if you used all radials, but you may have the last laugh, I have READ that in next years 17th regs all sockets under 20amp rating in domestic will need rcd protection .
So when every one is still trying to reset there split load boards,only your rcbo will be off.
The new 17thregs also appears worded ,so split load boards cause to much inconvenience to customers technically making them non conforming to regs and possibly the end of them.
Thus a new lease of life for standard boards and massive demand for rcbos
INFO FROM THE IEE WEBSITE but not confirmed till jan so not 100% sure if it will happen
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Postby sparx » Sun Dec 02, 2007 7:21 pm

Hi again,
let's take a step back and look at all wiring.
As qualified leckies we are allowed to install any kind of circuit we like.
There never has been a requirement for rings circuits in regs.
The only restriction is that we must be prepared to show our calcs. in respect of total load on each circuit plus volt-drop calcs.
To prevent us having to 're-invent the wheel' each time we do a job those nice people at the IET have done some sums for us and come up with 3 standard circuits , the domestic ring, & 2 domestic radial designs, which if we keep to the rules for each exempt us from redoing the calcs.
This is similar to scaffolders who also should design each scaff. but there are 'standard types' such as 'bird-cage', ' independant' ect, which are repeated so often they no longer have to be redesigned every time.
Note the 3 types of circuit called A1, A2, A3 are ONLY applicable to domestic locations, ALL comercial/industrial circuits MUST be supported by design calcs.
At a recent ECA organised 17th ed. seminar, the IET man said they were leaning away from rings as a move towards EU harmonisation,
so it's up to the individual to use whatever circuit he likes as long as calcs. justify method.
A case in point which comes up on 'trade only' forums regularly is the conversion of redundant cooker feed to a 'Sub-main' feeding a local kitchen ring. certainly not a standard circuit but if done safely and calcs. work is quite 'legal'
BTW lighting circuits are radials not rings as far end not returned to board
As I listed b4 3 basic circuits in use but are not exclusive,
regards SPARX
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Postby xjs1200 » Mon Dec 03, 2007 3:38 pm

Hi guys,

It's amazing how much valuable information we can learn from this forum and educate ourselves without putting our lives at risk. I've been to different countries in the continent and saw that they use radial circuits for sockets instead of rings, and also all of them are protected by RCDs (from the consumer unit). In addition, all installations use single cables in conduits within the walls. As far as I can see, they are perhaps more regulated than we are, but it's nice to know where the concept of the ring comes from.

Thanks!
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