Ring main.

[JKMRK1]

Question I have is, is it ok to have x2 ring main circuits on one 32amp type B MCB??

If so does this meet the current regs.

TIA.

 

[John clark]

I'm not saying I would do this because I wouldn't install like this, but I am going to play devils advocate.

Which regulations does such an arrangement breach?

And how would two ring final circuits installed in accordance with the regulations connected to the same 32A MCB be dangerous?

As I say I wouldn't do it, except as a temporary measure to restore supply, so I'm just curious about the thought process behind the statements.

common sense prevails in this case

 

[ebee]

common sense prevails in this case

Agreed, Common sense says it is not dangerous. Common sense say it does not breach the regs. But common sense tells us that it is not the most elegant of solutions and that it may well allow those who go there after us to confuse themselves. Therefore most of us would probably avoid it.
I did actually use this scenario (once) because quite a few new circuits got added as the job was ongoing so my planned spare ways got used up .

I made diagrams and notes next to consumer unit and appended to EIC to clarify to the unwary, plus labels on conductors too. 6 months later he got rid of another circuit to the remainder so I took the opportunity to normalise the situation

 

[davesparks]

It just gets peoples backs up IMO, and adds nothing to the debate. I know he disagrees without the red cross because I've read his previous posts!

By that logic none of the little pictures add anything to the debate.

 

[radiohead]

By that logic none of the little pictures add anything to the debate.

They don't, and neither do all of the posts on any debate.

 

[ebee]

So its had a name given to it now, bow tie circuit . ha ha
Cant wait to see that in any text book.

I doubt it will get into any text book. Any name might be equally as good (or bad) as another. I personally have never seen in any textbook or article the name Lassoo circuit (6.00 T & E radial feeding a 2.5 T & E ring final) , not at all uncommon in a kitchen where an old redundant cooker circuit was disconnected and used to form a new kitchen ring. The name lassoo is quite common for it. I`ve never noticed it in the OSG or the like. I`ve never noticed tree circuits mentioned for radials either but they are just as valid too.
We all (me included) tend to look at non standard circuits and think "Hey that`s wrong" then we look again and relalise "no it complies" or sometimes "no it does not comply, but is safe" (the later for example is an umpteen radial 2.5 T & E each feeding 1 max twin or 2 max single sockets on a 32A MCB - providing that the terminals in the CU can accomodate it both mechanically and electrically of course).

 

[markythesparky]

Definitely two rings there are 4 cables in the MCB. I'm going to add another way and seperate them.

How do you know they are both rings? Have you tested them?
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@SparkyChick

I have been having similar thoughts,
I don't think its right, and its not something I would install as new.

however I have just been browsing the book, and nothing is jumping out to say I couldn't do it if I wanted to.

I think we can mostly all agree that it is certainly not best practice but if someone could point me to a reg number it would make me feel better.

Appendix 15, page 505.
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I fully agree that this is incorrect and should not have been done.

But having said that what are the apparent dangers? I don't see any particular danger attributable to this.

The definition of a circuit is based around everything that is connected to a single way in a distribution board, so this would still count as one circuit, although it is nom-standard.
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You can have two legs of a radial cir uit connected to an MCB, but that is not two circuits. Also it is not bad practice.

Beg to differ; appendix 15, page 506.

 

[Pretty Mouth]

How do you know they are both rings? Have you tested them?
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Appendix 15, page 505.
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Beg to differ; appendix 15, page 506.

Appendix 15, contrary to popular belief, is not regulation. It shows options for for the design of ring and radial final circuits.

I can't see anything in app 15 that prohibits 2 radials in one MCB, or even 2 rings.

 

[ebee]

Right, so we all in agreement then. Two/three/four/ umpteen rings in one fuseway32A is one circuit is compliant and is safe.
4,5,6,umpteen radials in one fuseway 20A with one twin skt max in each radial is no compliant but still perfectly safe.
both 2.5 T & E and both including all other considerations that would normally apply with rings and radials (including floor area served)

 

[markythesparky]

Appendix 15, contrary to popular belief, is not regulation. It shows options for for the design of ring and radial final circuits.

I can't see anything in app 15 that prohibits 2 radials in one MCB, or even 2 rings.

That doesn’t answer my question as to whether the OP had made sure that they are both rings.

In answer to your statement, whether it’s a Reg or not, the options it gives do not include bunching two rings into an OCPD (which by the way would be a figure of 8, which you test for when doing an EICR). If you decide to make up your own options then where will this end? The same applies for the next page (506) which is about radials.

BS7671 is ‘Requirements for Electrical Installation’ and as such should be adhered to as close as possible.

 

[ebee]

That doesn’t answer my question as to whether the OP had made sure that they are both rings.

In answer to your statement, whether it’s a Reg or not, the options it gives do not include bunching two rings into an OCPD (which by the way would be a figure of 8, which you test for when doing an EICR). If you decide to make up your own options then where will this end? The same applies for the next page (506) which is about radials.

BS7671 is ‘Requirements for Electrical Installation’ and as such should be adhered to as close as possible.

No, two rings one circuit is not what is meant by "figure of 8".

The figure of eight test is a test of ring conductors that allows R1 + R2 readings to be taken (fairly consistantly but not 100% exactly) from any point on the ring

 

[dodger421]

That doesn’t answer my question as to whether the OP had made sure that they are both rings.

Post 69 on page 3 mate:

I've carried out Continuity tests on all four conductors this evening to find it is 2 RFCs, both sets of circuit conductors have now been marked so they can be identified correctly. Also on closer inspection I've found an sorry looking 32amp breaker in amongst a load of other rubble which could of potentially been from the spare way in the Consumer? Orignally it looks as if these RFCs were both on there own MCB. Going forward I'll purchase a new breaker and seperate these two circuits to there own supply.

 

[Pete999]

Appendix 15, contrary to popular belief, is not regulation. It shows options for for the design of ring and radial final circuits.

I can't see anything in app 15 that prohibits 2 radials in one MCB, or even 2 rings.

That doesn’t answer my question as to whether the OP had made sure that they are both rings.

In answer to your statement, whether it’s a Reg or not, the options it gives do not include bunching two rings into an OCPD (which by the way would be a figure of 8, which you test for when doing an EICR). If you decide to make up your own options then where will this end? The same applies for the next page (506) which is about radials.

BS7671 is ‘Requirements for Electrical Installation’ and as such should be adhered to as close as possible.

Agree, and what are the Regs
They are a non statutory document to aid installers/designers design and install Electrical installations in compliance with the Electricity at Work Act, a statutory document.
If people are installing circuits, that have already been described as not being discussed in BS 7671, are we not complying with the E@WA?
It's all well and good when people say this and that circuit is safe, that's their assessment doesn't make it right, we should be complying with BS7671 to comply with the E@WA, these are my apinions,

 

[markythesparky]

Absolutely spot on. What on earth is the point in producing a book on how electrical installations should be carried out if an installer then makes up his or her own guildines? We go back to college every three to four years at substantial cost, to ‘learn how to use‘ this British Standard so why then ignore it?
Another thought, if some thing bad were to happen, and the circuit is of a design that isn’t in BS7671, the installer wouldn’t or have a leg to stand on. If something bad were to happen and the circuit was designed along the guidelines of BS7671 then the installer would be totally in the clear. Slam dunk! Ain’t worth the risk!

 

[DPG]

Absolutely spot on. What on earth is the point in producing a book on how electrical installations should be carried out if an installer then makes up his or her own guildines? We go back to college every three to four years at substantial cost, to ‘learn how to use‘ this British Standard so why then ignore it?
Another thought, if some thing bad were to happen, and the circuit is of a design that isn’t in BS7671, the installer wouldn’t or have a leg to stand on. If something bad were to happen and the circuit was designed along the guidelines of BS7671 then the installer would be totally in the clear. Slam dunk! Ain’t worth the risk!

The regs aren't supposed to be an A to Z of allowable circuits though. It's not painting by numbers, and a degree of experience may be used to tweak things.

 

[markythesparky]

No, two rings one circuit is not what is meant by "figure of 8".

The figure of eight test is a test of ring conductors that allows R1 + R2 readings to be taken (fairly consistantly but not 100% exactly) from any point on the ring

Sorry, a figure of 8 is a ring with an interconnection making it look like a figure of 8 diagrammatically. This could be a single cable linked across both halves of the ring or a single outlet with four cables at it. Either way it is by definition a figure of 8!

Based on your own description of a what you should expect to find in testing a ring, how would you take your R1 + R2 readings from the setup described in this thread and also expect them to be ‘fairly consistent’? That ain’t gonna be!

If your answer is going to be that there are two rings and they will be tested separately, then which set of readings of which ring would you allocate to that fused way on the certificate or report?
Ive had this argument on here before and all I can assume, based on your defence of it, is that a lot of you guys are practicing this method.
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The regs aren't supposed to be an A to Z of allowable circuits though. It's not painting by numbers, and a degree of experience may be used to tweak things.

‘Requirements for Electrical Installations’

From the dictionary:
Requirements - that which is required; a thing demanded or obligatory

Obligatory -required as a matter of obligation; mandatory.
incumbent or compulsory.

Mandatory -permitting no option; not to be disregarded or modified

BS7671 can be used in a court of law against you. Why would you ‘tweak’ it? You’d have no defence if your argument for what you installed didn’t stack up in court. And remember in a court of law they would employ an ‘expert witness’ who would more than likely be an engineer or similar and who would abide by BS7671 until the cows came home. It would be, as it mostly is in courts, your opinion against Mr ‘Expert Witness’s. Mr Justice would no doubt place him/ her in a higher plain than your good self as a lowly Sparks, and you will loose your arguement. As I said, it’s not worth the risk. There is no risk at all by doing it to the guidelines.
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But there's a spare way in this particular CU.

If there wasn’t the installer could have connected a leg of each ring in the CU to extend it, taking into consideration loads and floor area of course.