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.

 

[Pretty Mouth]

As someone who is not registered with a scheme, I try to look for ways to carry out my work without needing to get my 3rd party certifier involved (extra hassle and expense). It's possible that whoever put the 2nd ring on the same breaker as the 1st may have done it simply to avoid building control notification.

 

[Michael Hopwood]

I'm not saying it's correct just saying what I've seen. That's why I've asked the question to make sure its correct.
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Thanks for the advice it is much appreciated?

Depending on the area (in square metres) extend the ring. Failing that then use a spare way and create another ring circuit.

 

[Pete999]

Depending on the area (in square metres) extend the ring. Failing that then use a spare way and create another ring circuit.

Probably don't have a spare way, that's why there are 2 RFCs crammed into one OCPD maybe?

 

[DPG]

Going round in circles this

 

[ebee]

The short answer is electrically, if the rings comply in their own right with the regulations, they should be safe, but there are possibly implications with the installation not being split to minimise inconvenience and possibly danger from other factors (such as a loss of power to say life supporting equipment). It's unconventional and I don't think any of us would install like it, but certainly I would do it at a pinch to restore supply as a temporary measure.

Good answer SparkyChick.

Folk often get hung up on OSG which is just a conventional way of doing things for safety and compliance.

Lets consider two examples:-

House 1/
A ring final circuit on ground floor with 40 points.
Floor area served 70 sq m
Ring length end to end 40m
Majority of cable under floorboards
TN supply with Ze 0.23.
Consumer unit in middle of the house.
To be used by an "average" family.
Everybody happy so far?

House 2/
Same spec but the floors are solid so the points are drop fed which increases cable end to end length to 120m.
We then worry a bit about R1 + R2 and volt drop.
By doing as 2 rings we could make them 65m & 55m.
Oh that sounds better.
We might make them different ring final circuits on two different circuits so adding a bit more resliance to the installation. I think most of us would choose this remedy.
However, for instance, no spare fuseway. So we put all 4 ends on one fuseway.
All the considerations are the same as for house 1/ and we`ve improved R1 + R2 and volt drop considerations.

Providing that all the terminals in the consumer unit can hold all the conductors electrically and mechanically sound and we label conductors accordingly then ok.
A ring final circuit can have any topology just in the same way that a radial can.
This circuit might be described as a "butterfly" circuit.
A 3 or 4 ring circuit you might call a "clover" circuit.
By definition all of these circuits are just one circuit being connected to the fuse/breaker on one fuseway.
The circuit in 2/ could be argued as better than in 1/ because it`s improved the Zeds and volt drops.

I did have one person insist that if they found this scenario thay would remove one end of each ring and join them to create just one ring on that circuit. That does seem a bit silly but it is something many of us would initially consider I think.

 

[SparkyChick]

This circuit might be described as a "butterfly" circuit.

I think we've already establish a standard naming convention for this as per @David Prosser 's proposition in this post:-

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I think the standard is BS DP1 - Naming conventions for unconventional/unorthodox ring final circuits (1st Edition - 2020).

I've just heard ammendment 1 is due in a couple of weeks, C&G are working on a qualification so we can prove our competence... the standard is £75 a copy, the exam is £150 and I believe a corrigendum will follow for the single page document in a matter of days. Got to keep up with the IET in terms of quality control

 

[Risteard]

Final circuit. A circuit connected directly to current-using equipment, or to a socket-outlet or socket-outlets or other
outlet points for the connection of such equipment.
Ring final circuit. A final circuit arranged in the form of a ring (not figure of eight) and connected to a single point of supply.

Then settle for it being a final circuit which isn't a ring final circuit. Let's call it a double ring final circuit if you prefer. (Or call it a crap final circuit if you like - few will disagree.)

 

[pc1966]

Superfluous Home Intriguing Topology final circuit

 

[ebee]

Then settle for it being a final circuit which isn't a ring final circuit. Let's call it a double ring final circuit if you prefer. (Or call it a crap final circuit if you like - few will disagree.)

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.

 

[Mike Johnson]

I would prefer to call them "Bow Tie" circuits sounds more sophisticated don't you know, can't get on with "lollipop" circuits sounds very childish, "Dragon fly" or a "Damselfly" at least they have four wings, can't think of a "Butterfly" with four wings.

 

[Pete999]

I would prefer to call them "Bow Tie" circuits sounds more sophisticated don't you know, can't get on with "lollipop" circuits sounds very childish, "Dragon fly" or a "Damselfly" at least they have four wings, can't think of a "Butterfly" with four wings.

I prefer to call them an abortion, work of the Devil.

 

[telectrix]

I would prefer to call them "Bow Tie" circuits sounds more sophisticated don't you know, can't get on with "lollipop" circuits sounds very childish, "Dragon fly" or a "Damselfly" at least they have four wings, can't think of a "Butterfly" with four wings.

hate to correct you there, but like bees, butterflies do have 4 wings.

A butterfly has four wings, two forewings and two hindwings. They are attached to the second and third thoracic segments (the meso- and meta-thorax). Strong muscles in the thorax move the wings up and down in a figure-eight pattern during flight. ... It must then wait for the wings to dry before it can fly.

they also have 6 legs, so that could be 3 rings on a circuit.

 

[Mike Johnson]

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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I prefer to call them an abortion, work of the Devil.

The Work of the Devil is Clingfilm or is that the Devil spawn.

 

[DPG]

Am I on the right forum here?

 

[westward10]

Am I on the right forum here?

Beginning to sound like Mumsnet.