Crossover in ring circuit

[KeenPensioner]

HI, as my profile says I'm not a sparky and know my limitations. I'm trying to learn (for the sake of it only as I'll never do it) what tests for "Ring Final Circuits" are. I understand how the Tests 1, 2 and 3 are done but in one of the videos I watched the presenter (John Ward) mentions a "crossover" see image and says that this "could lead the current being shared in an undesirable fashion. I don't understand that.

 

[Pete999]

I got a 'dumb' from a bloke that joined in 2010, never posted or started a thread. Mind you, he must be a good judge of character.

In fact looking at his/her profile, he's done 6 dumbs, closely followed by 3 bad spellings & 3 olds.

Bit of a prat then? is he

 

[Deleted member 26818]

It should be its a ring, looks like this ( O), if you cut in to the Ring and measure ring continuity( R1 for example) it would be the same at the Fuse board and if we measured it at every socket as well it should be the same, providing you close it back to a ring at the Fuse board. When the Current hits the Ring it see the same resistance in the conductors and Flows accordingly,

My understanding is that the current is divided equally around the ring, therefore allow us to use a 2.5mm cable to be used on a 32amp MCB, if it took the shortest leg back, then surely you would have over current issue on the shortest section of of the Ring?..

Ok.
If you have a ring that is 4m long with 3 sockets each 1m apart, the middle socket would have the same resistance on each leg. The other two sockets would have different resistance on each leg at a ratio of 3:1.
A 20A load connected to the middle socket would see 10A on each leg.
A 20A load connected to either of the other two sockets would see 15A on the short leg and 5A on the long.

 

[kingeri]

Upton, if a load is half way round a ring final, the current will flow 50/50 along each leg, but if the load is closer to the DB on one leg, more current will flow on the shorter leg due to that shorter leg's lower impedance.
Beaten to it by Spinlondon who did a better job than me anyway..!

 

[Upton Sparks]

well I figure I'll throw you an informative, makes up for the Dumb!

I got a bad Spelling the a couple of weeks ago, it didn't bother me to much .., I thought it was quite funny as it was 5 months after the posting.

I guess he was slow at reading..

 

[Pete999]

well I figure I'll throw you an informative, makes up for the Dumb!

I got a bad Spelling the a couple of weeks ago, it didn't bother me to much .., I thought it was quite funny as it was 5 months after the posting.

I guess he was slow at reading..

Or just Slow???

 

[Taylortwocities]

, it didn't bother me to much ..

You got another one!
Just havin’ a larf …

 

[Pete999]

You got another one!
Just havin’ a larf …

None of my dumbs bother me and I have had a few some deserved some not

 

[elsparko]

You got another one!
Just havin’ a larf …

and another though technically it would be grammar error but there is no option.

 

[Upton Sparks]

Thanks Tatlor, I'm feeling the Love today mate I can tell yeah!

I Know What saying Peter, there just Words. But that's what you get for putting your head above the Parapet.

any off to read electrical science books, I Know what an exciting life I have!.

 

[Midwest]

Bit of a prat then? is he

I haven't a scobby dooh Pete, each to their own. I do get a bit tired & emotional now and then, often reflected in my spelling & grammar, and chat of total tosh, but I'm of the camp, that if you have something to add positive or not, just have the balls to say it, as opposed just ticking a little box

Incidentally, there was another member recently, who gave me a 'bad spelling', which was correct or wrong dependant on how arsed you are, but also never posted, started a thread or otherwise contributed, YOU KNOW WHO YOU ARE!

 

[Deleted member 9648]

I don't mind a dumb now and again..in fact I see I've got two on this thread now!
Another point regarding the current sharing thing, Zs is always highest at the furthest point on the ring, not what you'd expect if the resistance was equal at each point. (anticipating another dumb coming my way!!)

 

[Ian1981]

It’s why it’s good practice to have the heavier loads like in a kitchen in the middle part of the ring final circuit so current will flow equally through both legs and keeping the first 2 legs from the consumer unit short as possible, in practice it’s not always feasible tho.

 

[Ian1981]

I don't mind a dumb now and again..in fact I see I've got two on this thread now!

Have a like

 

[Upton Sparks]

Ok a Big apologies to all you clever clogg's I acknowledge my miss leading post and inaccurate comment, thank you for schooling to the correct position.

Top of the Class for Spinlondon and DPG!. well done boys,

Marconi sent me a private message yesterday explaining it very elegantly, what a nice guy!...

Any back to work and school for me...

 

[elsparko]

humour is often the remedy to problems, nobody should take anything personal that is said on here, i dont see it as any different to ribbing the guys i work with, not everyone gets a stellar apprenticeship where they cover a variety of works, i certainly dont know everything about the trade, everyday is a schoolday as they say