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Discuss Ring main. in the UK Electrical Forum area at ElectriciansForums.net
Hi - apologies if I’m just restating something already said as I’m late to the thread.
Early on @SparkyChick asked for the “Reg That Says No” to putting 2 RFC into one OCPD. My thought is Chapter 43, protection against overload. RFCs are a bit of a load management exercise and now we have possibly offended Reg 433.1.1(i) where the rated current of the protective device ( In ) is less than the design current ( Ib ).
Early on @SparkyChick asked for the “Reg That Says No” to putting 2 RFC into one OCPD. My thought is Chapter 43, protection against overload. RFCs are a bit of a load management exercise and now we have possibly offended Reg 433.1.1(i) where the rated current of the protective device ( In ) is less than the design current ( Ib ).
R
radiohead
Great contribution....I have been thinking for a while now that 325 posts in what this thread really needs is someone to re-say what has already been said several dozen times. Genius.
Last edited by a moderator:
D
davesparks
Legislated against? Please do expand on this and tell us which piece of legislation you are referring to?
You can find and view all current UK legislation documents for free here: Legislation.gov.uk - https://www.legislation.gov.uk/
All I can say is... subjectively it's wrong. Objectively it complies with the regulations, if you disagree and would like to convince me otherwise, please explain (a) how it violates the figure 8 test (the purpose of which is to look for interconnections between the legs of the ring at a point other than the origin, interconnections that could if ill-informed alterations were made result in a situation with the potential to overload a cable) and (b) which regulations it violates and why.
It's wrong, we all know it's wrong... explaining why with actual regulations is a little trickier. Please don't cite Appendix 15 (Informative)... it is not a regulation. Without wanting to offend, it's the regulations equivalent of 'The dummies guide to the ring final circuit as defined by regulation 433.1.204'. It provides a lot of compliant examples, but listing all possibilities would be an impossibility which is why it's informative, it's a quick start guide if you will. As best as I can tell the only actual regulation specifically about 32A ring circuits is 433.1.204, it's entirely possible I've missed some but I've looked hard whilst writing some of my replies to this thread because I wanted to be certain I was objectively correct, but I'm all ears if I've missed some.
Maybe we should look at this another way... how would you code this arrangement if you came across it on an EICR? Which regulations would you cite as those it breaks and why?
Remember... I'm really just playing devil's advocate but I am getting a little tired of late of the blind following of rules. The regulations are the bare minimum, we need to be able to think for ourselves, so if you feel like telling me which code Codebreakers applies to this situation, go right ahead and explain what justifies such a code, backing your explanation up with actual regulations and how the arrangement breaks them.
And for another fun exercise in analysing the twisted mind of this old bint... lets suppose I have a ring circuit and I ran out of 2.5mm on the job, only got an off cut left that's about 18 inches long, only had two more double sockets to sort out... kitchen job, all the cables clipped direct or in the void of a dot and dab wall, so I run a length of 6mm from a convenient place (before anyone asks how I managed to squeeze 2 x 2.5mm and 1 x 6mm in accessory terminals.. I love the new 3 way slimline Wago connectors that take 0.5mm to 6mm cable.. awesome for this kind of thinking... nice maintenance free Wagobox tucked out the way, great it was) to the first of the doubles and as they are next to each other, I use the off cut of 2.5mm to supply the other. Does that comply with the design criteria for a ring circuit supplied by a 32A OCPD? If not, why not? And if this complies... how does the situation described in the OP not?
It's wrong, we all know it's wrong... explaining why with actual regulations is a little trickier. Please don't cite Appendix 15 (Informative)... it is not a regulation. Without wanting to offend, it's the regulations equivalent of 'The dummies guide to the ring final circuit as defined by regulation 433.1.204'. It provides a lot of compliant examples, but listing all possibilities would be an impossibility which is why it's informative, it's a quick start guide if you will. As best as I can tell the only actual regulation specifically about 32A ring circuits is 433.1.204, it's entirely possible I've missed some but I've looked hard whilst writing some of my replies to this thread because I wanted to be certain I was objectively correct, but I'm all ears if I've missed some.
Maybe we should look at this another way... how would you code this arrangement if you came across it on an EICR? Which regulations would you cite as those it breaks and why?
Remember... I'm really just playing devil's advocate but I am getting a little tired of late of the blind following of rules. The regulations are the bare minimum, we need to be able to think for ourselves, so if you feel like telling me which code Codebreakers applies to this situation, go right ahead and explain what justifies such a code, backing your explanation up with actual regulations and how the arrangement breaks them.
And for another fun exercise in analysing the twisted mind of this old bint... lets suppose I have a ring circuit and I ran out of 2.5mm on the job, only got an off cut left that's about 18 inches long, only had two more double sockets to sort out... kitchen job, all the cables clipped direct or in the void of a dot and dab wall, so I run a length of 6mm from a convenient place (before anyone asks how I managed to squeeze 2 x 2.5mm and 1 x 6mm in accessory terminals.. I love the new 3 way slimline Wago connectors that take 0.5mm to 6mm cable.. awesome for this kind of thinking... nice maintenance free Wagobox tucked out the way, great it was) to the first of the doubles and as they are next to each other, I use the off cut of 2.5mm to supply the other. Does that comply with the design criteria for a ring circuit supplied by a 32A OCPD? If not, why not? And if this complies... how does the situation described in the OP not?
JBW175
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As it’s Easter and this thread isn’t long enough already, I thought I’d resurrect it.
found this on an EICR today. Old Wylex board, with 2 RFC’s into one 30A BS3036 rewireable OCPD.
Trust me, there is a forth wire, just can’t see it on the phot.
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/d28c8c6d-e96e-4cd2-84f6-c47ba55e726a-png.84046/ "[ElectriciansForums.net] Ring main.")
found this on an EICR today. Old Wylex board, with 2 RFC’s into one 30A BS3036 rewireable OCPD.
Trust me, there is a forth wire, just can’t see it on the phot.
ebee
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ebee
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Well if you could join the 2.5 ring to a 6.0 (or 4.0) radial, so long as it`s substantially half way around the ring then all the usual ring type considerations should pan out adequately. Again not elegant but hey ho. I feel the double triple or quadrouple ring is easier and just as valid as a single ring. Indeed, on one foru, I hasd a remasrk by someone saying theyd take one end of each ring asnd join them in the consumer unit thereby producing one ring. If it does not end up oversize (abnormal length) it would be OK but not an improvement though because you`ve then increased R1 +R2 from what it was (and therefore increased Zs) and you`ve increased volt drop too. If I found a two, three or 4 ringed circuit I would glance asgain but so long as all the sums add up and the connections are mechanically and electrically sound then hey ho not a defect. Not a standard circuit you`d find in regs informative appx 15 or in the OSG but nothing "wrong" with it.
Same as ""trees" branches yada yada on radials etc
Circuits can be unusual "strange" but still compliant and safe.
You could actually have a ring final with just one point on it. Again unusual and probably pointless but still compliant and safe
Same as ""trees" branches yada yada on radials etc
Circuits can be unusual "strange" but still compliant and safe.
You could actually have a ring final with just one point on it. Again unusual and probably pointless but still compliant and safe
Oddly enough @JBW175 post #330 from today is shown as older than @SparkyChick post #331 from 25 Aug!
Is it wrong or dangerous? Not really.
Is it worth coding? Probably C3 as it was most likely a separate circuit added to an existing OCPD due to some other factor, so it could be improved by separating it and having another OCPD (ideally RCBOs, but that is another discussion point).
Is it wrong or dangerous? Not really.
Is it worth coding? Probably C3 as it was most likely a separate circuit added to an existing OCPD due to some other factor, so it could be improved by separating it and having another OCPD (ideally RCBOs, but that is another discussion point).
And there are two #331 posts.
I'm getting postings via my email regarding 'connecting two rings into one protective device' which appear to be linked to another thread posted back in the Jurassic period.
My final answer is that there is nothing wrong as they are still separate circuits but is it safe? and that depends on the way each circuitis loaded.
If the loading is small on both rings then it will pass unnoticed. The heavier the loading the greater the electrical stress.
My final answer is that there is nothing wrong as they are still separate circuits but is it safe? and that depends on the way each circuitis loaded.
If the loading is small on both rings then it will pass unnoticed. The heavier the loading the greater the electrical stress.
JBW175
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i can see why it’s been done, looks original on a 1970’s 3 bed semi, only other 30A way was feeding the cooker.
it’s been coded C3, but the board was C2, so will get properly sorted when I put a new fully RCBO CU in along with other remedial works over the coming weeks.
ebee
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Yep. C3 just mean improvement recommended.
you could take one leg from each rfc and joint them in the board, leaving you one big rfc.
ebee
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C3 means a reg defect. If it`s not a C1 or a C2 then its a C3, but if not a defect it must NOT be coded at all.
Incorrect colour coding of conductors is one example of a C3
Soi disant
Esteemed
If each one is safe if on 2 devices, what makes them become unsafe when put on 1?
There aren't.
It isn't
But why, other than testing aggro?
By exactly the same logic we should not have any ring finals, because if the ring is broken then the circuit becomes 2 radials.
A figure-of-8 actually decreases the chances of a break leading to an overload potential.
My dad had his tv and video recorder into same plug. I think it would be safer than one of those cube adaptors hanging out the wall.
I've done the same in the past I must admit. In my own home. Not ideal, but as long as it is 2 small flexes and the cord grip secures them properly then not too bad.
ebee
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Afigure of 8 (meaning a bridge somewhere in the ring) means we can not be sure to which extent the current will flow in every scenario of current draw at any particular times .
The other meaning for figure of 8 is the test we deliberately do on an unknown circuit to see if such bridges exist.
If a ring is designed properly then the loading during is its lifetime is meant to approximate that current draw will not be unduly imbalanced therefore both legs of the ring might be expected to draw very very approximately similar loads.
That is achieved by placing outlets around the ring and not bunched by load x time or by concentrating heaviest loads in the middle one third portion.
Nobody would go to great lengths to actually measure such and make calculations (except for research) but any half decent contractor would take a few mins to make a mental note and perhaps alter things slightly from first idea to make current draw more equal.
That`s the point of having a ring (along with volt drop and R1 + R2) considerations.
We try to avoid much beyond imbalance exceeding 20 to 12 amps on a 32A ring.
The point of this thread on this forum is one ring final circuit (not ring main that`s an incorrect term and applies to something else). One ring final circuit normally consiste of one ring connected at the fuseway.
My ramblings however show thay 2 rings (or more) connected as one ring final circuit are not unsafe and not non compliant but hey yes it is an unusual set up. Just because it is not shown in the OSG as a standard circuit does not make it become "wrong".
Take a spur (spur meaning a branch off the ring, not a S F C U or F C U - again wrong term).
We can spur anywhere off a ring with no more than one twin socket, at any point or at any JB or at the fuseway. That leaves us with a single bit of 2.5 T & E on a 30 or 32 amp fuse or breaker. it passes on short cct and earth fauly but not on overload, the overload protection is provided by the twin socket having a max rating of 13A and the plugtops each having a 13A fuse in making 26A possible (though unlikely) drawn.
Just a note that use of those little "Death Cubes" should be avoided as a rule of thumb ( Cheapo 13a adadaptors 2 way unfused as it means you could have a total of 4 x 13amp plugtops in a twin socket) they could be plugged in at any point on the ring or spur and are best avoided.
Actually, just to be a bit naughty - what is unsafe about a large number of radials, each one having not more than one twin socket and all connected by say one 32A MCB. Not actually unsafe proving the joints are reliable both electrically and mechanically and all volt drop and Zs are catered for.
I wouldn`t like to see it but it would not cause piles of dead bodies to litter the place.
Soi disant
Esteemed
If I start with this:
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/1617360076641-png.84116/ "[ElectriciansForums.net] Ring main.")
and add a loop like this:
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/1617360138941-png.84117/ "[ElectriciansForums.net] Ring main.")
or if I start with this:
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/1617360198264-png.84118/ "[ElectriciansForums.net] Ring main.")
and add a link across the middle to end up with the same figure of 8, which cable(s) become at risk of being overloaded that would not if I'd done this:
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/1617360486923-png.84122/ "[ElectriciansForums.net] Ring main.")
?
The more paths there are for current to flow to each point of loading the less flows in any given one, not more.
Ignoring the practical realities of actually wiring it, a "full mesh" topology of interconnections
![[ElectriciansForums.net] Ring main.](https://www.electriciansforums.net/attachments/1617360838697-png.84124/ "[ElectriciansForums.net] Ring main.")
would minimise the current flowing in every single cable (apart, obv, from the ones from the OPD to the "first" and "last" sockets, but those cables are never affected by any interconnection topology anyway).
And the more connections you have the harder it becomes to turn the circuit into radials, or to create multi-socket branches, by cutting connections.
and add a loop like this:
or if I start with this:
and add a link across the middle to end up with the same figure of 8, which cable(s) become at risk of being overloaded that would not if I'd done this:
?
The more paths there are for current to flow to each point of loading the less flows in any given one, not more.
Ignoring the practical realities of actually wiring it, a "full mesh" topology of interconnections
would minimise the current flowing in every single cable (apart, obv, from the ones from the OPD to the "first" and "last" sockets, but those cables are never affected by any interconnection topology anyway).
And the more connections you have the harder it becomes to turn the circuit into radials, or to create multi-socket branches, by cutting connections.
Attachments
![[ElectriciansForums.net] Ring main.](https://electricians.s3.eu-west-1.amazonaws.com/data/attachments/57/57025-8b13f50b662d8e9e68d1fcd3080d9252.jpg)
Diagram 3 and 4 are the same, just one extra socket, what are you trying to prove? or diss-prove come to that?
N
nicebutdim
They should be viewed in the context of diagrams 1 and 2.
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