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.

 

[7029 dave]

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

 

[David Prosser]

But the hind wings are much smaller and not considered a lifting wing, they are there to counter balance the movement of the front wings hence the erratic flight, but a Dragonfly can hover.
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The Work of the Devil is Clingfilm or is that the Devil spawn.

The rear set of butterfly wings are not always smaller the orange sulphur for example have slightly larger rear wings.

 

[Risteard]

Well I called it a butterfly circuit, anybody can call it what they want, no problem. Just like the age old cooker circuit, modified cos cooker not needed so a ring produced from that point, some call that a "lolipop" circuit or a "lassoo" circuit (not implying a cowboy job I hope!). The butterfly or whatever you call it just like the lolipop can be a decent circuit designed using sound engineering judgement and be ok. The fact that they are not easily recognised as standard circuits does nothing to detract from that. It might confuse the unwary a little but you could ask "should they really be adding/modifying these circuits if they do not fully understand what they are doing?". Answer No, they could ask someone who does know though and there is no shame in that. There is no person who knows everything about everything.
I disagree about calling them crap circuits though.
Another example to consider is a radial circuit, be it lighting or power points. You might branch out at some point for instance 1 begats 2 begats 4 begats 8 etc etc, it is still a radial circuit, again with different topology but nonetheless sound (some call them "trees"), in fact you could start it off with two conductors (or more) at the CU and it`s still ok - might be a beggar to test though! - you`d have several ends for Zs. It is up to the designer if they want to create one circuit,

In my example No 2/ is actually better in terms of volt drop and R1 + R2 than example No1 is.

I wasn't referring to all non-standard circuits as crap. I'm not hygely in favour of four conductors in a circuit breaker etc. though. So it was this particular arrangement which I was suggesting that many might consider to be crap.

A ring supplied by a suitably sized radial feeder is something which I have absolutely no difficulty with, even though it is non-standard.

 

[ebee]

I wasn't referring to all non-standard circuits as crap. I'm not hygely in favour of four conductors in a circuit breaker etc. though. So it was this particular arrangement which I was suggesting that many might consider to be crap.

A ring supplied by a suitably sized radial feeder is something which I have absolutely no difficulty with, even though it is non-standard.

Whatever you label them does not really matter, they are not crap circuits, they may be decent reliable circuits if undertaken properly. The only problem is they are not commonly listed. BS 7671 tells you what to comply with it does not tell you how to comply. So long as you use sound electrical design it complies and is safe. No less so than if you use a bog standard ring or radial.

I can give one example of a circuit that probably does not comply but is nonetheless safe :-
a bog standard ring final circuit B32A MCB with a spur of one twin socket at the origin of the ring i.e from the fuseway. Compliant Yes. Now disconnect the ring but leave the spur in place, so now its a twin socket on a 32a mcb. we would not like the look of it but removal of the ring has not rendered it unsafe has it?

 

[Vortigern]

So like a dog with a bone I have been thinking about this. I can't quite get my head around EFLI test what route would the current take on such a circuit? If I took it at ring A say, would it go around ring B or just ring A and the substation?

 

[ebee]

So like a dog with a bone I have been thinking about this. I can't quite get my head around EFLI test what route would the current take on such a circuit? If I took it at ring A say, would it go around ring B or just ring A and the substation?

Easy, just the ring of that particular fault. Same as any circuit connected in your consumer unit.
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Easy, just the ring of that particular fault. Same as any circuit connected in your consumer unit.

The test would give the most onerous as the answer which should be the 65m ring part of the circuit

 

[Risteard]

Whatever you label them does not really matter, they are not crap circuits, they may be decent reliable circuits if undertaken properly. The only problem is they are not commonly listed. BS 7671 tells you what to comply with it does not tell you how to comply. So long as you use sound electrical design it complies and is safe. No less so than if you use a bog standard ring or radial.

I can give one example of a circuit that probably does not comply but is nonetheless safe :-
a bog standard ring final circuit B32A MCB with a spur of one twin socket at the origin of the ring i.e from the fuseway. Compliant Yes. Now disconnect the ring but leave the spur in place, so now its a twin socket on a 32a mcb. we would not like the look of it but removal of the ring has not rendered it unsafe has it?

I never suggested that any of them were unsafe. In fact I specifically stated that the circuit in question was not unsafe unless there was an issue with the connections to the four conductors at the origin.

 

[littlespark]

Going round in circles indeed... or going round in rings...

earlier in the thread.... much much earlier... it has been established by the OP that there is two rings from one OCPD. Tested, and not found to be one ring and two radials.
It has also been established that there is a spare way in the board, and a suspect damaged breaker, possibly removed from the board.

it is highly likely, Your Honour, that these two rings have been put together as a stop gap, Friday afternoon, temporary fix until Monday.... and was never returned to.

Discussing whether it is safe or not is a mute subject... because the OP, I believe has mentioned previously that he (or his electrical representative) will seperate the two rings into seperate ocpd’s as soon as he can.

I surmise from this that the case is now closed, and no further discussion is required.

 

[westward10]

Can you expand on that please your closing evidence is not clear

 

[scootknew]

what is the 2 ring mains supplying? 1 bedroom , 2 bedrooms, /// livingroom + kitchen etc?

 

[Pete999]

what is the 2 ring mains supplying? 1 bedroom , 2 bedrooms, /// livingroom + kitchen etc?

Most likely the whole dwelling.

 

[Mike Johnson]

Just an aside, does anyone else have page lengths of 100 posts? Seems excessively long to scroll down to the last post.

 

[ebee]

Hi,
the point I was making is that if we wish to comply with BS7671 then we do not need to stick to the standard circuits, there are other alternatives.

Most of us, including me, if we see a non standard circuit then we initially think "hey that`s wrong!" because of familararity. But, if we consider further then we realise those circuits are indeed ok and often compliant with BS7671 too. We all fall into the trap of thinking something uncommon must automatically be wrong.

You often get things cropping up due to Part P.
Part P is part of the Building Regs in England and Wales and as such is the law (unlike BS7671).
Then they created the approved doc P, that is just guidance, nothing else, not law.
Originally the approved doc stated following BS 7671 or an Equiv European standard should satisfy the requirements. Nothing in Part P or the approved doc forbad following the rules of any civilised country. Later years the app doc only mentions BS 7671.
That does not make BS 7671 a legal requirement by statute.
The only time it becomes a legal requirement is you are a scheme member and that means you have a contract with that scheme to follow BS7671 in your workings. It is contract law, that`s all.
All Part P says is that reasonable provision must be made for safety and not much else really.

Things tend to become legends.
Having said all that, the most sensible option to cover yourself is to always comply with BS 7671 and my point is that the lassoo and the two ringed one circuit, and radial trees all comply, no matter how odd they look at first glance.

 

[G1ZQC_David]

Unless you have tested it a visual assessment that four conductors equate to two ring final circuits may or may not be correct. It could be four radials, one ring final and two spurs or just all four interconnecting with themselves.

If it were four radials on a 32 a MCB, its wrong anyway, as a radial curcuit requires a 20a MCB, 2.5 mm wire is only 26 amp rating.!!

 

[ebee]

If it were four radials on a 32 a MCB, its wrong anyway, as a radial curcuit requires a 20a MCB, 2.5 mm wire is only 26 amp rating.!!

Agreed, it would be wrong (probably) it would not be any more hazardous than a spur on a 32A ring though. So 4 or more radials of not exceeding one twin socket of good length (not excessive length so it compromises volt drop and Zs though) would also be OK ref overload, Two singles would but the reason why 2 single per spur was dropped was because at least one of them was likely to be converted to a twin at a future point in time.

Of course any of us seeing it would think "Oh No" including me, even though it usually would be quite safe