Lighting Ring???

B

Big_Spark

We had a call-out today from a client to look over a new property they have bought. They needed to know how much work was required to bring it up to BS7671:2001.

Anyway, our Sparky was doing the PT&I and found that the lights, upper and lower, were both RINGS!!

The cooker, was a RING!! in 4mm T&E...but oddly complies with the Regs as the overall circuit rating is adequate for it's use and the use of parallel conductors is permitted!

The Building failed in some ways..the lights, although a ring, have no earth core as they have been wired in 2 core flex (0.75mm)

Each socket appeared to be a Radial, until he lifted the floor to see which ones were connected to what, and discovered that the ring was feeding two JB's, that were linked together to form the ring, and the sockets on the upper and lower floors were spured off the JB's!

The Earth's were connected in the sockets, unsleeved, but not all were connected at the JB, and those that were had been simply twisted together outside the JB with no sleeving.

The supply to the garage was a piece of 2.5T&E clipped along the back wall, but it came off a 40A BS3036 fuse (Yes it had 40 fusewire in it) and fed about 10 sockets plus the lighting in the Garage and the garage door motor!

The Guy that lived their was into DIY apparently..but not too good at it..he put in the kitchen, which is falling apart, the plumbing needs replacing almost in entirety from all accounts..

But it struck me when I was told the lighting was a RING..cos a lot of people have posted here and called it a lighting ring, when it is not..Mad world!
 
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Excuse my ignorance - and I should add that I do know that lighting is not generally wired as a ring. But.......Why not???

Surely returning the cable to the fuse board cannot make the circuit dangerous??? My understanding is that sockets are wired in ring mains as this effectively doubles the capacity of the cable, so why not use a thinner cable for lighting circuits and wire that into a ring as well??? Or use the same size cable and wire it into a ring which will enable more lights to be powered from the same circuit??? Or have I got hold of completely the wrong end of the stick??? :confused:

Talking about ring mains - I know that these are not generally used on the continent but why not??? Does it come down to cost i.e. is it cheaper to wire a radial circuit in 4mm2 than it is to wire a ring in 2.5mm2???

Dont worry - I am not thinking about changing my rings to radials and vice versa. Just curious thats all :)
 
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You think that's bad, Jim

I found a lighting ring that was a proper ring in 2.5- beautiful job- with a 32A breaker back at base!!!
 
B

Big_Spark

Guys, your missing the point, which could be because of how I posted it..but the rest of the install was the real issue..although I have never is 21 years come across a lighting ring!!
 
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Davey,
Wiring lighting circuits in a radial circuit is the way its normally done and during fault finding or maintenance the electrician may think the supply to the lighting circuit is dead but it is actually back-fed through the ring. Its the same situation with socket ring mains but at least the electrician knows to look out for it. I have always thought that ring main wiring is a more dangerous form of wiring and in many countries they wire socket circuits in radials. A ring circuit is a cheaper way of installing sockets - especially in larger floor spaces.
 
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Just as I thought - there is no technical argument against wiring a lighting ciruit in a ring, it is just not the "done thing".

As an amature electrician, my opinion (for what it is worth) is that nobody should work on a circuit without ensuring that it is dead. Consider when driving - just because traffic should always give way, does that mean that you dont look before you cross a junction? Of course it doesnt!!!

If I do any electrical work I always throw the main switch to isolate the whole system before I commence work. However I accept that professional sparks are under much more pressure to get the job done quickly and minimise disruption!!!

Sorry - it sounds as if I am having a go and I am not. But, just cause things are normally done "A" does not mean that "B" is dangerous or inferior - the real danger is people assuming "A" all the time.
 
B

Big_Spark

Lighting circuits should never be on a RING circuit. This is bad design and potentially very dangerous.

Considering a lighiting circuit is never usually on a ring, there is always the potential for the two sections of the circuit to be split onto seperate MCB's if someone believes them to be two wholly seperate circuits being fed from one MCB. In this situation you have a real danger for fire or serious electric shock hazard.

It is NOT safe, NOT accepted practice, AND according to the IEE and NICEIC Technical handbooks is a no no.
 
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Davey

There is a 'Safe Isolation Procedure' for domestic isolations
 
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With no experience, talking to a friend with experience, he said that he does not use ring at all lighting or socket outlets, the reason is that if you have a wire of 2.5mm2 with MCB 32A, and one half of the ring cuts off than we have two radial circuits with 2.5mm2 wire and 32A MCB when the limit for radial circuit sockets is 20A...and the wire can take (in tables)27A, does it make sense?
Albert
 
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FWL_Engineer said:
Lighting circuits should never be on a RING circuit. This is bad design and potentially very dangerous.

Considering a lighiting circuit is never usually on a ring, there is always the potential for the two sections of the circuit to be split onto seperate MCB's if someone believes them to be two wholly seperate circuits being fed from one MCB. In this situation you have a real danger for fire or serious electric shock hazard.

It is NOT safe, NOT accepted practice, AND according to the IEE and NICEIC Technical handbooks is a no no.

please don't think i'm trying to argue with you FWL and obviously i'm not going to do this but would the following be fair to say:

In terms of theory (not good practice, in complience with regs etc..)


Wiring lighting circuits in a ring, would increase the load capisity of the circuit and would be perfectly safe.

Your above comments are noted along with limitations of ceiling roses etc.
Thanks Declan.
 
B

Big_Spark

Wiring lighting circuits in a ring, would increase the load capisity of the circuit and would be perfectly safe.

NO is the simple answer. A Lighting circuit and a Ring main are two different beasts, they operate differently and are used differently, you cannot apply the same principles to one as you do the other.
 
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FWL,

have you ever come across 2.5mm used on a lighting circuit?

I have recently, it was on a commercial property, didn't know whether commercial have different standards?

VERY small office.

P.S. please don't shout at me I'm feeling poorly... :cry:

:D
 
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i can see 4 reasons for using it

1: you want/need to get the job done in that visit and you run out of 1.5mm

2: the cable is very long so you need it for voltage drop reasons

3: the breaker is more than 10A (but you need to make sure the switches and fittings are up to it in this case)

4: there is some horrible derating factor involved
 
B

Big_Spark

I have come across this quite often. There was a spate a couple of years back, for consultants to spec 4mm for rings and 2.5 for lights in commercial premises.

The thinking behind it was that the heat generated by all the plant if the void areas where the cables run has a negative effect on them and so they would derate the circuit, thus upgrading the cable accordingly.

The 4mm for sockets has been stuck to by some but not by others, generally the 2.5 for lights has gone as terminating 2.5's into Klik roses and similar accessories was a nightmare that caused far more problems than it ever solved.

Now, many commercial installation have a habit of specing FP200 for the lights, this gets over the heating effects caused by the plant for 1.5 as FP has a higher operating temperature. The Foil in the sheath tends to dissipate the heat, according to the theory, and thus allows the cable to operate in mildly harsher environments without having to be derated.
 

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