Planning Kitchen Wall Electrics - Is This Good? [PIC]

[securespark]

you could take 3 cables from a jb on the ring nearby and connect one to each socket.

I was trained that you should only take one.

Terminals in both accessories and junction boxes limit the number of conductors in any one terminal.

Flameport has spoken:

"Each socket outlet or junction box on the ring can only have one spur connected. Trying to connect two or more is not only very difficult due to the number of wires involved, it can also result in an abnormally high load at that point in the ring."

As far as regs go, you could argue 3 things:

1. Manufacturer's instructions: as I don't have the latest copy, is this still in the regs? (134.1.1 & 510.3 refer)

2. 134.1.4

3. I know it is in the OSG, but there is this, which could be construed as only taking a single spur from each point:

H2.4 Spurs

"Such a spur should be connected to the circuit at the terminals of a socket-outlet or junction box, or at the origin of the circuit in the distribution board."

 

[ban-all-sheds]

With this radial circuit (all the accessories are sockets), how many sockets are connected directly in the circuit, how many unfused spurs there are, and how many sockets on unfused spurs there are in total?

 

[securespark]

Sorry, are you feeling ignored?

 

[John D v2.0]

With this radial circuit (all the accessories are sockets), how many sockets are connected directly in the circuit, how many unfused spurs there are, and how many sockets on unfused spurs there are in total?

It's a radial, there are no unfused spurs, they're all fused by the origin.

 

[securespark]

Click on the top link.
https://www.google.co.uk/search?q=A...eid=chrome&ie=UTF-8#q=Appendix+15+corrigendum

Page 4. Make of it what you will.

 

[EFLImpudence]

I hear what you're saying. There is stuff in the OSG that is not backed up in the margins by a regulation number.
But does that mean you can ignore the advice?

Well, yes.

a) It quotes worst case scenarios for those who don't know what they are doing. That's why it says things.
b) It has no authority; it is just written by someone.
c) If it disagrees with or adds to 7671, it is obviously wrong.

Surely if that were the case, the OSG would not include that information?

I don't know why it contains any information - apart from (a) - nor why it is compulsory for scheme membership.

 

[EFLImpudence]

I was trained that you should only take one.

Ok.

Terminals in both accessories and junction boxes limit the number of conductors in any one terminal.

So - if you haven't yet reached that limit ...

"Each socket outlet or junction box on the ring can only have one spur connected. Trying to connect two or more is not only very difficult due to the number of wires involved,

It's not difficult, though, is it?
However, if there isn't room for the conductor then you are not able to do it.

it can also result in an abnormally high load at that point in the ring."

Then it should not be done at that point, so
is it alright where that would not be the result?

What about
As far as regs go, you could argue 3 things:
1. Manufacturer's instructions: as I don't have the latest copy, is this still in the regs? (134.1.1 & 510.3 refer)

What have manufacturer's instructions to do with adding spurs?

2. 134.1.4

If it is, then it must be alright.

3. I know it is in the OSG, but there is this, which could be construed as only taking a single spur from each point:
H2.4 Spurs
"Such a spur should be connected to the circuit at the terminals of a socket-outlet or junction box, or at the origin of the circuit in the distribution board."

That's stretching it a bit.

 

[securespark]

Manufacturer's instructions regarding spurs: If the accessory/ junction box states it will only take (eg) 3 x 2.5 max, then you cannot connect more.

 

[John D v2.0]

Manufacturer's instructions regarding spurs: If the accessory/ junction box states it will only take (eg) 3 x 2.5 max, then you cannot connect more.

True, the way round would be with a JB - you could fit many more, even with wagos you could have 6 spurs from one JB https://www.tlc-direct.co.uk/Products/WA108.html

 

[EFLImpudence]

Manufacturer's instructions regarding spurs: If the accessory/ junction box states it will only take (eg) 3 x 2.5 max, then you cannot connect more.

Ah. I see.

Well yes, don't use that one, then.


I will say, every time I mention 4mm² spurs as a simple solution to connect two single sockets on a spur instead of the allowed double,
I do expect some debate regarding the regulations and electrical consequences - of which there is none.

That is fair enough, but pointing out this thing or that is too small to do it is not really relevant.

 

[John D v2.0]

You've convinced me there are no regulations to prohibit it, as long as you balance the ring enough.
However I'm not sure if you understood my diagram/calculation showing that 4mm spurs are not (except in special cases e.g. centrally positioned) the same balance than the exact same ring. I assumed your point was that it's up to the designer to make sure things are balanced (which I can't argue against) but now it sounds like you're saying no extra design is needed?

As an aside, the balance issue is exactly why figure of 8 / crossed rings are not allowed, and you have to specifically test that there are no cross connections. The 4mm cable is effectively a cross connection at the point the spur starts.

 

[EFLImpudence]

You've convinced me there are no regulations to prohibit it, as long as you balance the ring enough.

Ok.

However I'm not sure if you understood my diagram/calculation showing that 4mm spurs are not (except in special cases e.g. centrally positioned) the same balance than the exact same ring.

I don't know what the green figures mean.

I assumed your point was that it's up to the designer to make sure things are balanced (which I can't argue against) but now it sounds like you're saying no extra design is needed?

No, obviously it is needed.
I don't know to what you are specifically referring.

As an aside, the balance issue is exactly why figure of 8 / crossed rings are not allowed, and you have to specifically test that there are no cross connections.

I don't know that they are expressly forbidden.
The special dispensation allowing ring circuits does not mention them so, presumably no one would do it.

However, I think you will find that the bridge, depending on where it is, significantly reduces the problem with ring balancing, especially by primarily reducing the length of the ring for close to origin sockets.

The 4mm cable is effectively a cross connection at the point the spur starts.

No, it isn't.
It is just a 'normal' spur only connected to one leg of the ring.

 

[John D v2.0]

I don't know what the green figures mean.


No, obviously it is needed.
I don't know to what you are specifically referring.


I don't know that they are expressly forbidden.
The special dispensation allowing ring circuits does not mention them so, presumably no one would do it.

However, I think you will find that the bridge, depending on where it is, significantly reduces the problem with ring balancing, especially by primarily reducing the length of the ring for close to origin sockets.


No, it isn't.
It is just a 'normal' spur only connected to one leg of the ring.

The green figures are basically how far round the ring the load is, where 0.0 is the CU, 0.5 is the mid point, and 1.0 would be back at the CU again. Clearly 0.0 and 0.5 are ideal, because the load is shared evenly between the legs, and <0.01 would be worst, because >99% of the current would flow through the shorter leg.

I think by saying things like "depending where [the bridge] is, you're emphasising the role of careful design. Agree a shorter ring is certainly better for close sockets, but in the general case, a ring intersecting with arbitrary point on a ring would need careful design (and be unnecessary).

I am specifically referring to:

I will say, every time I mention 4mm² spurs as a simple solution to connect two single sockets on a spur instead of the allowed double,
I do expect some debate regarding the regulations and electrical consequences - of which there is none.

I'm saying there are (change in balancing of the ring and therefore possibly changes needed to return the risk of overload of one of the legs)
=====
I do feel like we're going in circles a bit, I see your point that every circuit has to be designed and checked on its own merits. And I'm with you on the regs now.
But the only place I feel we differ is this which my diagram, although unclear, was trying to address

In this case, with the sockets on the shorter leg, it would actually better the balance as the long leg is now shorter.

My example showed that's not the case (although I now realise you pointed out that it can sometimes make things better, sometimes worse, which I realised is true) but it's not correct to say there are no electrical consequences without knowledge of the rest of the circuit.

 

[EFLImpudence]

Yes, we agree.

I've done another diagram.
This may not be practical but it is just an illustration.

Left is a bungalow with the ring in loft and drops to sockets.

Right is how it could be wired with 4mm² drops.
This could actually make it better for the ring when there are high load on outer sockets:

Obviously - connecting the 4mm² 'L's the other way round would not be a good idea - you have to think about it.

 

[JohnW2]

Hi folks. It has been suggested that I might have something to offer this discussion, so I have come out of hibernation (severe busy-ness) to see if that's true. I haven't yet read the whole thread, but, in terms of this recent posting ...

However, I think you will find that the bridge, depending on where it is, significantly reduces the problem with ring balancing ....

I think Mr Kirchoff would agree with you. If one connects a 'bridge' between two parts of a ring (or, indeed, multiple bridges between parts of a ring), then I think it is inevitable that the current will reduce in the leg of the ring which was previously ('pre-bridge') carrying the higher current, and that the the current will increase in the leg of the ring which was previously ('pre-bridge') carrying the lower current - i.e. 'balance' of the ring would be improved.

We've discussed this matter many times before, and I think the consensus has generally been that, in functional terms, turning a ring into a figure-of-eight is advantageous, the main downside being the nightmare that may result in terms of testing and fault-finding, particularly for someone unaware of the presence of the bridge(s).

Kind Regards, John