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.

 

[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?

 

[ebee]

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

LOL.

yes it is a ring final cct not a ring main.

You might find a ring main in the street.

You might find a ring main at a power station etc (although not really the type you find in the street.

A ring final in installtions - domestic or otherwise

 

[Dustydazzler]

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?

 

[Soi disant]

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

I haven't used the term "ring main".

I've used "ring final" and just "ring".

 

[DPG]

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

Pete, I think you might have quoted the wrong person.

 

[Pete999]

Pete, I think you might have quoted the wrong person.

probably did in my state of mind, going to give up for a while far to much goin on in my bonce at the moment might even have to resign?

 

[DPG]

probably did in my state of mind, going to give up for a while far to much goin on in my bonce at the moment might even have to resign?

You can't do that Pete, you're an institution!

 

[ipf]

probably did in my state of mind, going to give up for a while far to much goin on in my bonce at the moment might even have to resign?

Don't jump, mate. Have a laugh, we still want ya.

 

[littlespark]

That’s what being in a hive mind does to you. Pete the Borg.

 

[telectrix]

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?

i was referring to the poster who drew all those figure 8 etc. circuits.

 

[Soi disant]

Pete, I think you might have quoted the wrong person.

probably did in my state of mind

It happens. A few times (not here) in the past I've had "discussions and debates" (ahem...) lasting multiple posts where I've misattributed what had been said. The arguments over what had been said were valid, but with the wrong person.

Worse things happen at sea.

 

[Soi disant]

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.

Bring back (and uprate) the octopus....

 

[Soi disant]

i was referring to the poster who drew all those figure 8 etc. circuits.

That'll be me.

And I would like to get out more.

But I'd probably still have done the drawings - they only took a few minutes and were easier to use to make my point than words. ?

 

[littlespark]

Worse things happen at sea.

Yeh.... like Sea Shanties....

 

[James]

Yeh.... like Sea Shanties....

Your day in the barrel?

 

[ebee]

So we are all agreed then?