Ring main.

[Mike Johnson]

Then why are diagrams 3 & 4 there.

 

[nicebutdim]

That's explained in the text.

 

[Soi disant]

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.

Didn't Marbo (?) used to make a plug designed to take more than one flex?

 

[DPG]

Didn't Marbo (?) used to make a plug designed to take more than one flex?

That rings a vague bell, but not sure. Need to have a Google me thinks.

 

[ebee]

Soi disant,
Nice diagrams and well put.
Yes I like it.

Ok the point I was making.

With a bridge that makes a ring final become a "fig 8" it means that we tend to lose control of which leg gets more of the current x usage factor. A I said we don`t usually go to great lengths do control this however we do a quick approx to see if it looks badly slanted in favour of one leg or the other and then perhaps re-adjust our plan in order to balance it up a bit. This helps with heating issues and therefore aging of cables and helps reduce overloads of cables.

I`m not suggesting that fig 8 or indeed that lovely matrix thingy you drew for use is going to cause fires and threaten life everytime it`s used, far from it.

It is complicated enough to make predictions even with a well designed ring final and the fig 8/matrix complicates this further.
In reality, much of the time, no great problems should arise from it and if every ring final was done that way I don`t think we`d find streets littered with dead bodies.

However, of all the differing combinations of power drawn at various points around the ring then this arrangement is far more difficult to follow, calculate and therefore enjoy the most reasonable aspects of ring benefits as originally conceived for current flow considerations. It also makes it difficut to test properly too (OK that one can be said, to a degree, about the 2, 3, 4, umpteen rings on one ring final circuit too!)

 

[Soi disant]

It's testing which is the problem, I think. Without the predictability/consistency of readings from a proper, single, ring it's harder to spot problems such as multiple socket spurs.

But as for loading and balance - I won't mind if I prove myself wrong with some worked examples, (or if someone else does to save me the effort ?), but my initial feeling is that any cross-connections which make a figure of 8 or anything else just add current paths and thus lower the current flowing in them, not increase it.

I can sort of envisage a scenario where a section near the origin of the ring could become unbalanced, but I'm not sure how improbable it is. Need to do some sketches.

Anyone out there with circuit design software which could be used to analyse different scenarios?

 

[Pete999]

It's testing which is the problem, I think. Without the predictability/consistency of readings from a proper, single, ring it's harder to spot problems such as multiple socket spurs.

But as for loading and balance - I won't mind if I prove myself wrong with some worked examples, (or if someone else does to save me the effort ?), but my initial feeling is that any cross-connections which make a figure of 8 or anything else just add current paths and thus lower the current flowing in them, not increase it.

I can sort of envisage a scenario where a section near the origin of the ring could become unbalanced, but I'm not sure how improbable it is. Need to do some sketches.

Anyone out there with circuit design software which could be used to analyse different scenarios?

Not really other than it's not called a ring main a ring main is a distribution circuit it's ring final circuit if you get your terms correct you may get some better responses

 

[telectrix]

If I start with this:

View attachment 84116

and add a loop like this:

View attachment 84117

or if I start with this:

View attachment 84118

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:

View attachment 84122

?


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

View attachment 84124

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.

youneed to get out more. don't the pubs open soon?

 

[Dustydazzler]

Ringadingadong

 

[Pete999]

youneed to get out more. don't the pubs open soon?

If you are referring to me Tel, then nothing gets up my snout more than Wannbee's quoting something they know little or nothing about post ban waiting, still no one likes the truth these days do they?