Ring Final Circuit (RFC) versus Radial. Yes, again.

[pc1966]

Once a Ring is Infected with numerous spurs on spurs on spurs , it can no longer be called a Ring and must be called a Spider circuit which needs to added to the 19th Edition assuming Rings aren't outlawed before that

If you have a badly butchered RFC where properly fixing it is impractical then simply dropping the OCPD to 20A is a fix.

Yes, there might be an issue of total load but unless folks rely on heaters off sockets (instead of fixed electric, or gas/ASHP sort of system) it is unlikely. I have seen 20A RFC before off rewirable fuses, I guess due to high-ish Ze at the original design time, and they worked fine for decades.

 

[pc1966]

I hope my point has come over correctly, I'm not condoning broken rings, high resistance connections, or undersized cables, and I fix them all. I'm just pointing out that in reality having a 2nd chance of getting back to the CU safely isn't a bad thing and even a broken ring (while not technically safe) usually comes to no harm in practise.

Those are good points about fault tolerance. In these days of RCD everywhere it might be less of an aspect, but I have seen an RFC with open CPC (r2) and all sockets still had an acceptable CPC to meet ADS so remained safe.

On a radial with open CPC the first you would know (other than a sparky testing it) might be last you ever knew!

 

[Dustydazzler]

If you have a badly butchered RFC where properly fixing it is impractical then simply dropping the OCPD to 20A is a fix.

Yes, there might be an issue of total load but unless folks rely on heaters off sockets (instead of fixed electric, or gas/ASHP sort of system) it is unlikely. I have seen 20A RFC before off rewirable fuses, I guess due to high-ish Ze at the original design time, and they worked fine for decades.

Come across ALOT of old Council houses in my area which have 1 Ring for the entire houses sockets, which have been seriously infected now with multiple spurs on spurs etc.
De rating the OCPD to 20amps will often cause nuisance tripping when the house is just one Ring for every socket in the house.
I call these completely fooked Rings

 

[pc1966]

De rating the OCPD to 20amps will often cause nuisance tripping when the house is just one Ring for every socket in the house.

If it includes a modern kitchen then you have trouble. The fact the kitchen fitters did it badly is sadly par for the course

 

[telectrix]

all depends on the load. up to 27A ( less if derated of a ring. arting factors involved) a radial is king. personally, 'd rather have 2/3 radials i advanta

 

[telectrix]

using your knowledge of regs, and design of a circuit/s , you install radial or ring accordingly. not bloody rocket science, is it? 2nd ywar apprentice should know all this.

 

[pc1966]

2nd year apprentice should know all this.

They should, the evidence is they don't.

Also a lot of courses teach folk to do and not always to think. I was hoping to cover the why of some choices and methods here.

 

[telectrix]

i refer my learned friend to post #16.

 

[pirate]

I am grateful to @pc1966 for starting this thread in a non-adversorial manner and summing up many factors for consideration.
I'm a radial man...but can see ring advantages... I don't have the experience of many of you, so maybe the "simple" radial appeals. I like a long "wander" lead, it makes testing a bit easier, but on a small installation there's maybe a good reason to go radial all the way.
Whatever, I look forward to the discussion!

 

[mainline]

Those are good points about fault tolerance. In these days of RCD everywhere it might be less of an aspect, but I have seen an RFC with open CPC (r2) and all sockets still had an acceptable CPC to meet ADS so remained safe.

On a radial with open CPC the first you would know (other than a sparky testing it) might be last you ever knew!

Radial.

Break in CPC = socket outlet with no CPC = risk of electric shock = RCD disconnect when imbalance occurs.

Break in ring final = no detection of fault as only one line conductor has slipped out = 2 x 2.5 mm cables with a best case scenario current carrying capacity of 27A (surface clipped) protected by a 32A MCB = Overloaded cable = Possibility of a fire.