Ring Main

[securespark]

A term often used for a Ring Final circuit. But looking at this Static Caravan board, it was used by manufacturers as well. No wonder Joe Public gets confused...


Talking of confused, this 4 way strip from the same 'van has 13A embossed on every outlet...

 

[Iggifer]

That looks like a nice woodscrew under the RCD

 

[phatboy]

I'm wondering how that second 'LIGHTS' MCB is operated!

 

[ericmark]

The ring final is rather a special system with special rules which allows us to use some predetermined figures.

In spite of having a 32A MCB we calculate at 26A that 20A at centre and 12A even spread across the ring.

As we drop the MCB size the 20A remains so using a 20A MCB we only reduce the current rating by 6A not 12A. So reducing the current does very little to the volt drop which is the limiting factor.

With a static caravan it is unlikely you will ever have a problem with volt drop so I see no point in using a ring with a B20 MCB.

However the question is why is there a B20 MCB it could well be so than MCB trips before the supply MCB/Fuse opens. It could have been designed to use a 32A MCB but swapped to a B20 latter.

It could also be the other type of ring which allows for a section to be isolated without turning off the whole system.

But I would guess it is simply the consumer unit comes with pre-printed labels and the installer has just selected the most appropriate.

 

[333rocky333]

That looks like a nice woodscrew under the RCD

I think hager do use countersunk threaded machine screws

 

[Adam_151]

I think hager do use countersunk threaded machine screws

They might do, however unless I'm mistaken, and I am hoping SS will confirm, that CU will have a name along the lines of "plug-in-systems" moulded into it. Wood screws to secure the front and a lack of space are standard features and 90% of the time they use Hager devices.

 

[Simon35]

A term often used for a Ring Final circuit. But looking at this Static Caravan board, it was used by manufacturers as well. No wonder Joe Public gets confused...


Talking of confused, this 4 way strip from the same 'van has 13A embossed on every outlet...

I don't think Joe Public gets confused, more likely it's of no importance to them...

 

[JohnW2]

The ring final is rather a special system with special rules which allows us to use some predetermined figures. ... In spite of having a 32A MCB we calculate at 26A that 20A at centre and 12A even spread across the ring.

Although you frequently quote those figures, and although they seem to make very reasonable sense as a 'rule of thumb', I don't think anyone has ever seen them in writing, have they? Logically speaking, if there is such an officially-accepted 'formula', one would probably expect essentially the same 'formula' to also apply to a 32A radial circuit - have you heard that suggested?

As we drop the MCB size the 20A remains so using a 20A MCB we only reduce the current rating by 6A not 12A. So reducing the current does very little to the volt drop which is the limiting factor.

I can't think of any real reason why anyone would design a 2.5mm² ring protected by a 20A OPD, since the whole point of a ring final is that the regs give a special dispensation to allow the use of smaller CSA cable than a 30/32A OPD could normally protect. If VD (or EFLI) would be a problem with a 20A 2.5mm² radial, then one would presumably design with higher CSA cable, rather than change it to a ring, wouldn't one?

Kind Regards, John

 

[securespark]

I don't think Joe Public gets confused, more likely it's of no importance to them...

Beg to differ. Many DIY folk call Ring Finals Ring Mains and many DIY folk think that each 3 pin outlet is rated at 13A.

What I'm saying is that it is not surprising that people get the wrong idea when manufacturers mislead this way.

 

[Simon35]

I don't think Joe Public gets confused, more likely it's of no importance to them...

Beg to differ. Many DIY folk call Ring Finals Ring Mains and many DIY folk think that each 3 pin outlet is rated at 13A.

What I'm saying is that it is not surprising that people get the wrong idea when manufacturers mislead this way.

So are you saying you think it's important that the general public call ring finals by their correct name? Personally, I don't.

No doubt that there are many fields of work where the non-specialist in that field/general public doesn't have quite the correct terminology, no doubt we all use the wrong term for something, but because this is an electrical forum then you attach more importance to it.

 

[JohnW2]

I don't think Joe Public gets confused, more likely it's of no importance to them...

Beg to differ. Many DIY folk call Ring Finals Ring Mains ...

They do, but it doesn't result in any confusion - we all know what they mean. The same when they talk about 'bulbs', 'plugtops', 'plug sockets','low voltage lights' or 'transformers' etc. etc.

....and many DIY folk think that each 3 pin outlet is rated at 13A.

Those outlets in the picture probably are 'rated at 13A', aren't they?

What I'm saying is that it is not surprising that people get the wrong idea when manufacturers mislead this way.

It's hard to disagree with that. The ideal would obviously be for everyone to use 'correct terminology' (as determine by someone!) and Joe Public cannot be blamed for taking his cues from what terminology manufacturers, wholesalers and retailers use. Mind you, it doesn't help when the industry itself uses questionable terminology (like 'continuity testing' for a quantitative measurement!)!

Kind Regards, John

 

[EFLImpudence]

So are you saying you think it's important that the general public call ring finals by their correct name? Personally, I don't.

So are you saying you see no requirement for any form of education?

What a ridiculous attitude but it explains a lot.

 

[Simon35]

So are you saying you think it's important that the general public call ring finals by their correct name? Personally, I don't.

So are you saying you see no requirement for any form of education?

What a ridiculous attitude but it explains a lot.

So you have extrapolated my saying that I don't think it's important whether the public calls ring finals ring mains, because it leads to no confusion, to me saying I see no requirement for any form of education?

Clearly, that is not what I have said.

Thanks for the insult by the way.

 

[JohnW2]

So are you saying you think it's important that the general public call ring finals by their correct name? Personally, I don't.

So are you saying you see no requirement for any form of education?

Since we're being pedantic, even "ring finals" (which is what most electricians seem to call them) is actually sloppy (aka 'incorrect') terminology - it should be "ring final circuits".

What a ridiculous attitude but it explains a lot.

So long as electricians persist in referring to quantitative low resistance measurement as 'continuity testing', I will reserve judgement on that one!

Kind Regards, John

 

[Simon35]

So are you saying you think it's important that the general public call ring finals by their correct name? Personally, I don't.

So are you saying you see no requirement for any form of education?

What a ridiculous attitude but it explains a lot.

So you have extrapolated my saying that I don't think it's important whether the public calls ring finals ring mains, because it leads to no confusion, to me saying I see no requirement for any form of education?

Clearly, that is not what I have said.

Thanks for the insult by the way.

Having just trawled through a few recent threads, I can see that correct terminology is quite a hot topic at present...

Anyway, it's no different electricians calling themselves electrical engineers. It leads to no confusion in the lives of the general public.