Ring and Radial

[crystal ball]

I just wonder how the rest of the world has managed without them, (with a few exceptions)

 

[JohnW2]

I just wonder how the rest of the world has managed without them, (with a few exceptions)

One obviously does not 'need' them. However, whilst we all know the theoretical potential problems, I'd be interested to know to what extent (if any) electricians have actually come across significant realisations of those theoretical potential problems. In other words, if they really do represent 'a problem' one could equally ask how we have managed for 60-70 years with them.

Kind Regards, John

 

[chivers67]

Is there any reason that a small 2 bedroom house can't be wired with a ring circuit upstairs and a radial circuit downstairs. Each would be fused to regulations. (The kitchen would be on a separate ring circuit).

I often run ring finals still.

Not everyone does but for Radials I also run a separate Earth cable to the last radial socket

 

[JohnW2]

Not everyone does but for Radials I also run a separate Earth cable to the last radial socket

Fair enough. As I wrote:

... what I would argue is that IF one would feel more comfortable with CPC redundancy, then one should implement it, one way or another (but should also take into consideration any downsides of the method of implementation one chooses).

Kind Regards, John

 

[EFLImpudence]

One obviously does not 'need' them. However, whilst we all know the theoretical potential problems, I'd be interested to know to what extent (if any) electricians have actually come across significant realisations of those theoretical potential problems. In other words, if they really do represent 'a problem' one could equally ask how we have managed for 60-70 years with them.

That's not really the point.

Rings were introduced to upgrade BS 3036 15A radials to 30A without replacing the existing wiring; merely extending it back to the fuse box including additional sockets. 15/0.725 = 20.68.

That this resulted in CPC redundancy (with 1mm² CPC) could only have been an consequential bonus and not a supplementary reason otherwise it would be required elsewhere.

 

[EFLImpudence]

Not everyone does but for Radials I also run a separate Earth cable to the last radial socket

I would just ask Why? Well, I know why it's done but why do you do it?

With that do you use separate earth terminals at each accessory?
Do you do the same on single load circuits?

 

[JohnW2]

Rings were introduced to upgrade BS 3036 15A radials to 30A without replacing the existing wiring; merely extending it back to the fuse box including additional sockets. 15/0.725 = 20.68.

Where does that come from? The usual story is that they were introduced (primarily for new builds and rewires) because of the (often fairly marginal) reduced copper usage at the time of the immediate-post-war copper shortage, isn't it?

Kind Regards, John

 

[EFLImpudence]

Is that not the same difference? Upgrade existing and install in new.

That was the result, either way.

 

[deadshort]

Actually you are both correct.

DS

 

[JohnW2]

Is that not the same difference? Upgrade existing and install in new.

I'm a bit confused. You make it sound as if it is relevant that one was upgrading a 15A BS3036 radial - but the same argument would surely have held if one had been upgrading a 16A or 20A MCB radial with 2.5mm² cable (had the MCBs or metric cable existed then). On reflection, I'm also a bit confused by:

Rings were introduced to upgrade BS 3036 15A radials to 30A without replacing the existing wiring; merely extending it back to the fuse box including additional sockets. 15/0.725 = 20.68.

Was this perhaps just because it didn't require an additional fuseway? If one had a spare fuseway available, one could have done as you say, connecting the new cable to a separate (new) 15A BS3036, but not bothering to connect the new cable to the existing circuit - one would then have two 15A radials - and 15A x 2 = 30.

KInd Regards, John

 

[chivers67]

Not everyone does but for Radials I also run a separate Earth cable to the last radial socket

I would just ask Why? Well, I know why it's done but why do you do it?

With that do you use separate earth terminals at each accessory?
Do you do the same on single load circuits?

EFLI - Regarding Radials I do this just in case someone in the future decides to change their accessories or another owner down the line a CPC pops out and the sockets further along are still protected. I think it's good practice, just like earthing back boxes with one fixed lug with a plastic accessory. Someone comes along one day changes it for metal and even if they "don't know" what they're doing one would hope they place this CPC into the earth terminal into the new accessory still. I do that it might stop someone dying in the future due to another persons mistake?

Ring finals: separate CPC from back box earth terminal to adjacent/nearest accessory terminal and other two CPCs into other side. Single CPC at both ends doubled over or normally I'd use a reel of braided Earth cable to save the bother of messing about with sleeving.

Single load circuits? No - should I

 

[EFLImpudence]

I believe the additional fuse way was a factor.

To upgrade (or install) a 30A radial would have required an increase in cable csa of two cable sizes of what was available.
As it would be today if still using 3036 fuses - 15A,2.5mm²; 30A, 6mm².

 

[EFLImpudence]

EFLI - Regarding Radials I do this just in case someone in the future decides to change their accessories or another owner down the line a CPC pops out and the sockets further along are still protected. I think it's good practice, just like earthing back boxes with one fixed lug with a plastic accessory. Someone comes along one day changes it for metal and even if they "don't know" what they're doing one would hope they place this CPC into the earth terminal into the new accessory still. I do that it might stop someone dying in the future due to another persons mistake?

Ok. but future idiots are not really your concern however laudable.

Ring finals: separate CPC from back box earth terminal to adjacent/nearest accessory terminal and other two CPCs into other side.

If installing HI earthing, which is what you are doing, then the ring CPC should be connected to separate terminals otherwise the occurrence against which you are protecting may still happen.

Single load circuits? No - should I

Can the same thing not happen on single load circuits.?

 

[Risteard]

I often run ring finals still.

I too support the ring final circuit.

 

[JohnW2]

I believe the additional fuse way was a factor.

As far as I can see, it was probably the only factor, because ....

To upgrade (or install) a 30A radial would have required an increase in cable csa of two cable sizes of what was available. As it would be today if still using 3036 fuses - 15A,2.5mm²; 30A, 6mm².

Indeed - but, as I said, if one had a spare fuseway, one could have installed a second (or installed two, if starting from scratch) 15A radial without the need for any increase in cable size at all.

Kind Regards, John