Have the rules for ring mains changed over the years?

[Mike Johnson]

For upstairs lights, I usually wire all the bedrooms on one lighting circuit, and landing and any passage lights on another. That way, you either have light in the room or just outside it.

That's fine, but the CU that needs to be found is usually on the ground floor.

 

[nicebutdim]

For upstairs lights, I usually wire all the bedrooms on one lighting circuit, and landing and any passage lights on another. That way, you either have light in the room or just outside it.

It's usual over here to supply landing light from ground floor circuit.

It makes sense in some ways, but I've never liked it. Your reasoning is sound and makes me question my thinking.

 

[brianmoooore]

If there are only two lighting circuits, then I would connect the landing and passage lights to the downstairs circuit. Any 2G switches will have both halves on the same circuit, and no 'borrowed' neutrals.

 

[narkedatninety]

You actually said "who's sole purpose is to detect a breach of the dielectric barrier within the run of cable"

Dielectrics are materials that don't allow current to flow. An insulator.

Dielectrics are classified based on molecular structure and polarisation mechanism. Classifications includes capacitors, transducers, photonic/ferroelectric devices but, yes, the insulation you mention does include a dielectric constant. It certainly forms part of the barrier.

 

[pc1966]

That's fine but i wasn't arguing that RoW uses radials because they can't use rings; more that the fact they don't use them proves they're not needed to install perfectly safe and operational installations. Rings are simply unnecessary.

They are not necessary. Neither are radials either.

But the RFC is efficient and effective for its intended purpose of general sockets around a larger area, it also lends itself to better fault coverage during testing.

The same logic can be applied to parallel feeds. They are not necessary but if you have every had the misfortune to try and wrangle cable like 120mm and above you would be cursing the designer for not use two that are not quite so " anaconda on ------" to deal with.

I also think it's preferable to have different rooms or different sections of the home on different breakers. We're encouraged to split between floor levels but imo splitting between sections or rooms is much more preferable.

It is a trade-off. How much more effort in running each circuit back to the CU? How much more cost in the RCBOs (or coming soon for a small premium AFDD for all)?

Also how often do you meet an installation with a fault in the fixed wiring that is not a direct result of botched DIY? It happens for sure, but probably less than faulty appliances.

And this leads back to another less considered aspect of the EU versus UK plugs. With fused plugs if there is a hard fault then often the fuse will go as well as the breaker tripping. Reset the breaker and all comes back on except the faulted appliance as it has been isolated by its fuse blowing.

With unfused EU plugs you would need to either know which on has faulted, or unplug all and go round plugging them back in until BANG!

That is another nice aspect of UK sockets, though sadly underused, they are (usually) switched. So you can plug in and switch on and have less of a brown trouser moment of plugging in to a live fault should it occur.

Finally on the UK sockets, they have the safety shutter that is lacking in most of the rest of the world. True, the determined child or idiot can defeat that protection but it raises the bar somewhat to poking stuff in to holed to find out what happens...

 

[mainline]

Dielectrics are classified based on molecular structure and polarisation mechanism. Classifications includes capacitors, transducers, photonic/ferroelectric devices but, yes, the insulation you mention does include a dielectric constant. It certainly forms part of the barrier.

You have steered away from the point i made about your incorrect statement of a cpc's sole purpose being to detect a breach of the dielectric barrier within the run of a cable.

 

[narkedatninety]

You have steered away from the point i made about your incorrect statement of a cpc's sole purpose being to detect a breach of the dielectric barrier within the run of a cable.

I believe you misunderstood and still misunderstand the point so we'll agree to disagree and move on.

 

[mainline]

I believe you misunderstood and still misunderstand the point so we'll agree to disagree and move on.

I like to learn so if you could explain what you meant when you said
“a cpc's sole purpose being to detect a breach of the dielectric barrier “

How can that statement be correct when a cpc has other purposes ?

 

[davesparks]

And that's the problem - even those with qualifications to design installations are still stuck on this idea that all power has to be on rings.

Maybe some people are, but not everyone.

Maybe those designers you are so critical of actually have a good reason why they chose a ring over a radial circuit.
Do you have full details of the design and all decisions made within that process or are you just working from the end result of that process?

I've never been on a site in the UK where a radial has been used for power outlets, it's always rings.

Wow, you have obviously had a very limited experience of installations in the UK.

I think there are very few installations I've worked on where there hasn't been at least one socket radial.

 

[rewireIT]

Wow, you have obviously had a very limited experience of installations in the UK.

I think there are very few installations I've worked on where there hasn't been at least one socket radial.

I've been on site since i left school in the early 2000's.

I've obviously seen radials but they are the odd one out of a thousand - my point was (put badly, yes) that the design choice for the main power is always a ring. Yeah there might be some cupboard on the 5th floor with a couple of sockets on, on a radial. But it's 99%+ of the time rings in the design choice.

When designers are putting 2 sockets on ring finals, when said sockets are literally going to be used to run nothing but a hoover now and again, i question the competency of the designer.

 

[davesparks]

Adding an insulated layer to a dead conductor who's sole purpose is to detect a breach of the dielectric barrier within the run of cable is nonsensical from a safety perspective let alone an additional increased cost. Hence, there is a very good reason why we do not sleeve the CPC throughout the entire cable.

Yes there is a very good reason we don't insulate the CPC in T&E, in fact there are 2 reasons.
1, it's cheaper to manufacture
2, it would make the cable bigger overall and that is undesirable.

The CPC doesn't have a sole purpose of anything, it has more than one purpose.

I'm not following with your idea that the CPC is there to detect a breakdown in the dielectric barrier, could you expand on this please?
If this was the case then surely a metal tape/foil would be included in the cable which emcompases the insulated live conductors? In a T&E cable the bare cpc would only be capable of detecting this for a small part of the dielectric barrier wouldn't it?

Plus monitoring equipment is never installed to make use of this function of the CPC that you suggest.

 

[davesparks]

I've obviously seen radials but they are the odd one out of a thousand - my point was (put badly, yes) that the design choice for the main power is always a ring.

I still find this surprising, all of the installations I work on have both rings and radials used where suitable for general use power.

Recently I've even had a job where I converted 2 radials into 1 ring circuit as the radials just couldn't supply the required power for the evolving use of the offices.

When designers are putting 2 sockets on ring finals, when said sockets are literally going to be used to run nothing but a hoover now and again, i question the competency of the designer.

Undoubtedly that is lazy design but I wouldn't call someone's competence into question over it!
If its a large installation then that kind of lazy design work may be a result of over-reliance on software for design.
It could also be a general spec put in place by someone higher up that makes it more cost effective to install a ring.

 

[littlespark]

I must be a bad designer.

When i converted the back of my garage to a utility room, i put in a 32A rfc for a washing machine, tumble dryer and one double socket.... For the sake of a few inches of cable between the two isolator switches, and the hassle of wresting 2x 4mm's in the back of a grid switch.
I chose rfc over radial for that particular circuit where either would have done, purely for my own selfish needs.

 

[nicebutdim]

Undoubtedly that is lazy design but I wouldn't call someone's competence into question over it!
If its a large installation then that kind of lazy design work may be a result of over-reliance on software for design.
It could also be a general spec put in place by someone higher up that makes it more cost effective to install a ring.

A colleague once mentioned that completing their design qualification was both a waste of time and also a real eye opener where choice of circuit design was concerned. Primarily it helped them understand why certain choices might have been made, where previously they could ascertain no logic.

At my age it's likely not something I'll ever bother completing, but that comment has stuck with me and has since prompted me to try to look at circuit design from many more perspectives than before - admittedly, many choices still appear to make little sense

 

[davesparks]

The same logic can be applied to parallel feeds. They are not necessary but if you have every had the misfortune to try and wrangle cable like 120mm and above you would be cursing the designer for not use two that are not quite so " anaconda on ------" to deal with.

The worst case of this I have seen is the feed to the dimmer room in a theatre.

400A supply via a 400mm 4 core SWA, one of many questionable electrical design decisions in that theatre!

 

[Mike Johnson]

Those UK electricians with OCD would love the French staggered RCD and MCB's connected together with a staggered busbar, it is very neat, even vertical bus bars to connect RCD's above each other in different rows.

The only thing I can think that could be a compromise on UK plugs, if using a mobile appliance when you reach to limit of the cord It puts a strain on the connection, plug and socket, in the French flat plug it just pulls out of the socket and stops the machine working, would seem a bit safer.

 

[nicebutdim]

Those UK electricians with OCD would love the French staggered RCD and MCB's connected together with a staggered busbar, it is very neat, even vertical bus bars to connect RCD's above each other in different rows.

Pictures?

 

[Mike Johnson]

Been looking, but I can't find my L'installation électrique - David Fedullo , Thierry Gallauziaux will have another looks later.

 

[Mike Johnson]

The picture on the front of this book illustrates the idea: Installer ou rénover un tableau électrique - Thierry Gallauziaux ,... - Librairie Eyrolles - https://www.eyrolles.com/BTP/Livre/installer-ou-renover-un-tableau-electrique-9782416004360/