Are people moving away from rings

[MG201]

hi all I’m just wondering are the forum members moving away from doing ring circuits and doing radials instead ? I have been reading that this may be the way industry is going wether this is to aid in the introduction of AFDDs I don’t know , obviously AFDDs won’t work in rings, that’s why I recon radials will have to be standard before AFDDs are used.
There will no doughy be some sparks who install AFDDs on rings which will defeat the purpose of them , ( if I’m right )
Should all new builds now be installing radials ??

 

[Taylortwocities]

Its a matter of circuit design. Most domestic circuits can be satisfied with radial circuits, but you may need more than one to satisfy the higher-current requirements of today's houses (washing machine+tumble dryer+dishwasher+ other stuff).
In the old days a single ring final was enough for yer average house. And that was the norm for decades, and new electricians were guided by the old crusty sparks who said "that's the way its always been done"

Personally, I'm a fan of radials. Easier to install, test, and to fault find. What's not to like?

 

[Pauls0212]

am I missing something here... why wont an afdd work on rings???

 

[JAWS]

am I missing something here... why wont an afdd work on rings???

I found this..

AFDD’s have another blind spot – Ring circuits. A ring circuit, is, as the name suggests a circuit that forms a ring, starting and finishing at the consumer unit, they are commonly used in the U.K. The chances are all the sockets in your property are part of a ring circuit. The problem with ring circuits is as follows; you won’t know that the ring has a break in it. If the electricity tries to flow round the cable and comes to the break it won’t try and jump it and create an arc, it will take the long way round the rest of the ring. You’re not aware there’s a problem as all your sockets still work, the AFDD’s not aware there’s a problem as there’s no arc. Please note though this will only apply to a series arc fault in a ring circuit not a parallel arc fault.

 

[HappyHippyDad]

Its a matter of circuit design. Most domestic circuits can be satisfied with radial circuits, but you may need more than one to satisfy the higher-current requirements of today's houses (washing machine+tumble dryer+dishwasher+ other stuff).
In the old days a single ring final was enough for yer average house. And that was the norm for decades, and new electricians were guided by the old crusty sparks who said "that's the way its always been done"

Personally, I'm a fan of radials. Easier to install, test, and to fault find. What's not to like?

I must admit I'm never too sure why we install rings.

A few things put me off one type of radial though (or at least makes me think twice about it). With regards a 4mm radial protected by a 32A MCB:

1. The 4mm has a CCC of 37A with reference method C, with all other reference methods it's <32A so if anything changes in the house which alters the ref method then there could be problems.

2. It will likely cost more as the only extra cable used with a ring will be from the final socket back to the CU, compared to the 50% extra price of 4mm cable compared to 2.5mm.

3. Having never tried 3 x 4mm conductors in a socket terminal I am not sure if they fit. Do they? If not, this will limit the versatility that makes a radial attractive.

 

[Silly Sausage]

Personally, I'm a fan of radials. Easier to install, test, and to fault find. What's not to like?

A problem with radials with multiple points on them is, if you get cpc discontinuity part way along, every point downstream has no Earth, which will only be revealed by testing or someone has the misfortune to discover a L-E fault.

 

[Boing89]

I must admit I'm never too sure why we install rings.

A few things put me off one type of radial though (or at least makes me think twice about it). With regards a 4mm radial protected by a 32A MCB:

1. The 4mm has a CCC of 37A with reference method C, with all other reference methods it's <32A so if anything changes in the house which alters the ref method then there could be problems.

2. It will likely cost more as the only extra cable used with a ring will be from the final socket back to the CU, compared to the 50% extra price of 4mm cable compared to 2.5mm.

3. Having never tried 3 x 4mm conductors in a socket terminal I am not sure if they fit. Do they? If not, this will limit the versatility that makes a radial attractive.

Going back into the mists of time I remember being told during my initial electrical training that ring circuits were standard because you could use smaller cable. It was a resource thing following WW2 and it meant limited copper stretched further. I never looked into it any further and it could have been complete bobbins from my instructor at the time but it sounds plausible.

 

[Pete999]

I must admit I'm never too sure why we install rings.

A few things put me off one type of radial though (or at least makes me think twice about it). With regards a 4mm radial protected by a 32A MCB:

1. The 4mm has a CCC of 37A with reference method C, with all other reference methods it's <32A so if anything changes in the house which alters the ref method then there could be problems.

2. It will likely cost more as the only extra cable used with a ring will be from the final socket back to the CU, compared to the 50% extra price of 4mm cable compared to 2.5mm.

3. Having never tried 3 x 4mm conductors in a socket terminal I am not sure if they fit. Do they? If not, this will limit the versatility that makes a radial attractive.

Wire the radial in 2.5mm2 on a 20 Amp OCPD As per Appendix 15 BS 7671

 

[SJD]

Most new builds I see still have the sockets mostly wired as RFCs. Perhaps with odd exceptions e.g. something you want on a separate circuit wired as a radial.

Mostly I'm doing the same, though the last two ELECSA annual visits, the assessor has extolled the virtues of radials.

But as/when AFDDs do become affordable for domestic use, that might indeed be one reason to change.

 

[Flanders]

AFDD wil not work on a ring but will dectect an arc coming from an appliance such as dishwashers, tumble driers, washing machines, fridges etc , so may be of some use as there is always a story of one of these burning a house down , I wounder if there was An AFDD at Grenfell tower the fire might not of started in the first place. , I beleave they will also detect an ark between live and neutral on a ring .

 

[Deleted member 26818]

Perhaps Grefel tower wouldn’t have happened if the Council had installed AFDDs.
Then again, would they have been willing to splash out the cost of AFDDs, considering they couldn’t be arsed to pay the few pennies extra for non-flammable cladding?

 

[Deleted account]

3. Having never tried 3 x 4mm conductors in a socket terminal I am not sure if they fit. Do they? If not, this will limit the versatility that makes a radial attractive.

Some do some don't. Crabtree do, but click doesn't.

I'm a fan of radials and often do 2.5mm radials on 20A mcb and 4mm on 32A mcb for kitchens. At fsu's I enter as 4 mm leave as 4mm and take a 2.5mm after fuse to appliance. I never put three 4mm in one socket or FSU. It's a bit tight.

 

[Harry_P]

hi all I’m just wondering are the forum members moving away from doing ring circuits and doing radials instead ? I have been reading that this may be the way industry is going wether this is to aid in the introduction of AFDDs I don’t know , obviously AFDDs won’t work in rings, that’s why I recon radials will have to be standard before AFDDs are used.
There will no doughy be some sparks who install AFDDs on rings which will defeat the purpose of them , ( if I’m right )
Should all new builds now be installing radials ??

Regardless of afdds the modern technological efficiency of appliances means in an average house the only place where it makes sense to install a ring is in the kitchen,a radial circuit is usually more than adequate for the sockets outside of the kitchen.

 

[littlespark]

Re Grenfell.
Blame the appliance, blame the wiring, blame the cladding, blame the council, govt and fire service!

What about all the other fires that happen when it comes down to some prat, a lighter and the bin store? The blame will land on everyone but the prat.

Ring V Radial?
I'm afraid i'm still with the 2.5mm ring... and ill still call it a ring main circuit when im talking to customers.
I'm sure both designs have their plus points, as well as their negatives.

 

[Dave OCD]

I'll occasionally wire a 4mm ring as well.

 

[MG201]

I'll occasionally wire a 4mm ring as well.

What circumstances would you choose this option , I have a good idea but just reassuring my thoughts

 

[Dave OCD]

Well if the overall length was close to max Zs values, or in a kitchen with a lot of appliances- and also installation methods where insulation is everywhere for example. And I also like a bit of 4mm

 

[Toneyz]

The layout of outlets would be a design consideration.

 

[Dave OCD]

Yes that's what I was getting at in a roundabout way.

 

[Lucien Nunes]

I don't install general purpose circuits so I don't have to make this choice, but I would use 32A rings where appropriate if I did. They are an effective and flexible means of providing for a high total loading over a large area with a minimum number of redundant or little-used circuits. Whilst open to some theoretical objections, in practice they have served reliably for over 70 years.

It's important to make the distinction between two choices:
20A circuits vs. 32A circuits.
Ring circuits vs. radial circuits.

Obviously there is no difference in usability between a 32A radial and a 32A ring. But there is a difference between say two 20A circuits and a 32A circuit. Although the total current available from two 20A circuits is higher, you cannot plug two 13A loads in wherever you please, only one can be on each circuit, whereas on a 32A circuit they can be anywhere i.e. there is greater diversity so you can do more with a given total circuit capacity.

Horses for courses, I would say. And there you've got the betting ring, the parade ring...

 

[gnuuser]

Going back into the mists of time I remember being told during my initial electrical training that ring circuits were standard because you could use smaller cable. It was a resource thing following WW2 and it meant limited copper stretched further. I never looked into it any further and it could have been complete bobbins from my instructor at the time but it sounds plausible.

correct and the benefit of the ring circuit was that you didn't have as much voltage drop in the circuit because you had 2 points of supply on the circuit.
this effectively halved the distance calculations for voltage drop that you required for a radial circuit.
less voltage drop= smaller sized conductor being suitable for the job

 

[Deleted member 26818]

Not forgetting of course, that when RFCs were introduced, they were replacing multiple single point radials (each individually sized for the expected load) with a single multi-point circuit that could be used for a variety of loads.

 

[Shoei]

So RFCs aren't compatible with AFDDs because a break in a ring doesn't create an arc. Doesn't that make the ring safer because it's more fault-tolerant?

You don't want a break but better to find it on a routine inspection, rather than wire to increase the likelihood of an arc just so the AFDD can detect it.
Open to interpretation but I'd have thought protection against arcing with a single break is an argument in favour of rings.

 

[Deleted member 26818]

So RFCs aren't compatible with AFDDs because a break in a ring doesn't create an arc. Doesn't that make the ring safer because it's more fault-tolerant?

You don't want a break but better to find it on a routine inspection, rather than wire to increase the likelihood of an arc just so the AFDD can detect it.
Open to interpretation but I'd have thought protection against arcing with a single break is an argument in favour of rings.

Taking on board, that arcs can cause fires, then yes it would appear that an RFC is safer.
However, the fact that a break in the circuit would be undetectable and could cause one of the legs to be overloaded, which could also cause a fire, kind of negates the safety side of no arcs.

 

[Shoei]

Taking on board, that arcs can cause fires, then yes it would appear that an RFC is safer.
However, the fact that a break in the circuit would be undetectable and could cause one of the legs to be overloaded, which could also cause a fire, kind of negates the safety side of no arcs.

Fair point, but in real life it's not obvious whether more fires would result from arcs or overloads, worst case for a 2.5mm cable at 32A would be 15.2W/m which is warm but not catastrophic. I don't know, but arc faults could be a greater fire risk than overloads in most real installations. I'd like to see UK research-based evidence before calling it either way.

 

[Lucien Nunes]

Has anyone ever seen hard evidence of correctly-installed ring cables damaged by overheating specifically due to a break in the ring? (Obviously discounting localised heat damage from a faulty termination.) I haven't, and I suspect that far from causing a fire, the usual result of a broken ring is that the cables run a few degrees hotter than normal but still less than rated temp. Exceptional outliers where the full 32A load is all on one leg, and the cable installation method pushed the rating in the first place, might get warm enough to have their useful life slightly shortened.

By contrast, we've all seen connections burn up, which is what AFDDs are looking for.

 

[Deleted member 26818]

If we discount the overloading of one of the legs in the event of a break in a conductor, as being a safety issue.
Can we then discount the advice to ensure an RFC is not overloaded during normal use?

 

[Shoei]

If we discount the overloading of one of the legs in the event of a break in a conductor, as being a safety issue.
Can we then discount the advice to ensure an RFC is not overloaded during normal use?

No one has discounted overloading as a safety issue, the observation was about comparative risk from a fault condition. RFCs have a useful safety feature that they suppress arcing if a conductor breaks, but now we are asked to make an arc more likely so an AFDD can detect it. It's fair to ask whether that improves or degrades electrical safety.

What's the greater hazard, a 5000 degree plasma in part of a PVC cable, or a temperature rise of a few degrees along it's length? I don't know the answer but I'd like to see some UK evidence before dumping RFCs and adopting a solution designed for the hazards of American domestic wiring.

 

[Marti]

One of the most informative discussions I've read in here - thank you folk.

 

[Pete999]

Fair point, but in real life it's not obvious whether more fires would result from arcs or overloads, worst case for a 2.5mm cable at 32A would be 15.2W/m which is warm but not catastrophic. I don't know, but arc faults could be a greater fire risk than overloads in most real installations. I'd like to see UK research-based evidence before calling it either way.

Don't protect a 2.5mm2 socket radial with a 32 Amp OCPD should be a 20 Amp, 32 Amp radial will require 4mm2 Amendment 15 BBB.

 

[Flanders]

Deleted duplicate post

 

[Flanders]

No one has discounted overloading as a safety issue, the observation was about comparative risk from a fault condition. RFCs have a useful safety feature that they suppress arcing if a conductor breaks, but now we are asked to make an arc more likely so an AFDD can detect it. It's fair to ask whether that improves or degrades electrical safety.

What's the greater hazard, a 5000 degree plasma in part of a PVC cable, or a temperature rise of a few degrees along it's length? I don't know the answer but I'd like to see some UK evidence before dumping RFCs and adopting a solution designed for the hazards of American domestic wiring.

Looks like we need John Ward to do one of his experiments

 

[Mike Johnson]

I suppose eventually we will adopt the EU standard of dual MCB's and spur's, together with dedicated spur's for appliances, Brexit accepted.

 

[Mike Johnson]

Duplicate post?

 

[Pete999]

I suppose eventually we will adopt the EU standard of dual MCB's and spur's, together with dedicated spur's for appliances, Brexit accepted.

By Dual CBs I presume you mean DP CBs, as for appliances on their own dedicated circuit, a good idea in my book especially for the larger appliances greater than 2KW as an example.

 

[Shoei]

Don't protect a 2.5mm2 socket radial with a 32 Amp OCPD should be a 20 Amp, 32 Amp radial will require 4mm2 Amendment 15 BBB.

Agree, those numbers illustrate worst case if you have a 32A protected 2.5mm RFC, and it breaks somewhere, putting max current on one sector of the ring.

 

[Mike Johnson]

Most of the special circuits, that should be on an individual DP CB if I can remember them all are:
Washing Machine
Tumble Dryer
Oven
Hob
Dish Washer
Water Heater
UFH
Fridge On separate RCD
Freezer On separate RCD
Alarms
Outside dependancies
Garage
Electric heating inc ASHP
Towel Rails
Extract Fans
Max of eight sockets on 1.5mm protected by 16A
Max of twelve sockets on 2.5mm protected by 20A
No ring mains allowed
All lighting to have an earth running to them even if not used
Everything metal has to be earthed even if built into the walls
No T & E allowed all cables must be double insulated and of the same cross section
That's all I can think of at the moment, but if anyone is interested PM me and I can direct to the best information source.

 

[chrisdungan]

I'm a Kiwi sparkie ( actually a registered electrical inspector). I've worked in Eire and the UK 2007/8. in our part of the world ring circuits are almost completely unknown in domestic. Probably for the same reason you guys do rings. "Because that's the way we've always done it........"
There are pluses and minuses in both systems.
Here we usually wire our radial circuits in 2.5 stranded, the cheapskates will use 1.5. Yes I know seems weird to you guys but we wire domestic lighting circuits in 1.0mm. the only time we use solid conductor is in 1.omm all the other sizes are stranded!
So modern kitchens usually have 2 circuits with a separate circuit going to the separate laundry. In kiwi land we don't put clothes washers in the kitchen, they go in a serarate laundry room or a laundry space in the garage ( usually a double or treble in a bigger house)
These days that 2.5mm circuit will often be rated at 16amp rather than 20 because of our derating factors due to thermal insulation. RCDs are required and now AFDDs are becoming the norm.
Faultfinding and testing with radials is a breeze.
The only downside with a house full of radials and a switchboard full of CBs, RCDs and AFDDs is you need a minimum of 45 ways. 60 ways if you have PV and you live in the country with a water pump and septic disposal system. There are even some councils that now require rain water storage and pumping for non potable water like toilet flushing and garden watering in town.

 

[Deleted member 26818]

Have they done away with Licencing for Electricians now?

 

[Mike Johnson]

No you don't need a licence to be a SA

 

[Pete999]

No you don't need a licence to be a SA

What's an SA?

 

[Mike Johnson]

S as in Smart A as in, use your imagination, but your avatar has a plug attached to it.

 

[Deleted member 26818]

I was enquiring as to whether New Zealand had done away with licencing for Electricians.
I’ve been informed that they have, thought I’d ask a Kiwi whether it is in fact the case.

 

[Midwest]

I was enquiring as to whether New Zealand had done away with licencing for Electricians.
I’ve been informed that they have, thought I’d ask a Kiwi whether it is in fact the case.

That saw wrist is making you unusually cranky.

 

[Mike Johnson]

I was enquiring as to whether New Zealand had done away with licencing for Electricians.
I’ve been informed that they have, thought I’d ask a Kiwi whether it is in fact the case.

In that case you could have worded your original post better, it looks like one of those SA comments you get on here when someone ask's for advice.

 

[Deleted member 26818]

In that case you could have worded your original post better, it looks like one of those SA comments you get on here when someone ask's for advice.

Yep, I probably should have done.
Any chance of an answer to my question?

 

[Silly Sausage]

Most of the special circuits, that should be on an individual DP CB if I can remember them all are:
Washing Machine
Tumble Dryer
Oven
Hob
Dish Washer
Water Heater
UFH
Fridge On separate RCD
Freezer On separate RCD
Alarms
Outside dependancies
Garage
Electric heating inc ASHP
Towel Rails
Extract Fans
Max of eight sockets on 1.5mm protected by 16A
Max of twelve sockets on 2.5mm protected by 20A
No ring mains allowed
All lighting to have an earth running to them even if not used
Everything metal has to be earthed even if built into the walls
No T & E allowed all cables must be double insulated and of the same cross section
That's all I can think of at the moment, but if anyone is interested PM me and I can direct to the best information source.

Most of the first 15 items on that list is over engineering and a complete waste of resources and money.

 

[Deleted member 26818]

If it’s anything like the US, dryers are often 20A.

 

[Mike Johnson]

Most of the first 15 items on that list is over engineering and a complete waste of resources and money.

Well that's certainly one individual's opinion.

 

[Pete999]

Most of the special circuits, that should be on an individual DP CB if I can remember them all are:
Washing Machine
Tumble Dryer
Oven
Hob
Dish Washer
Water Heater
UFH
Fridge On separate RCD
Freezer On separate RCD
Alarms
Outside dependancies
Garage
Electric heating inc ASHP
Towel Rails
Extract Fans
Max of eight sockets on 1.5mm protected by 16A
Max of twelve sockets on 2.5mm protected by 20A
No ring mains allowed
All lighting to have an earth running to them even if not used
Everything metal has to be earthed even if built into the walls
No T & E allowed all cables must be double insulated and of the same cross section
That's all I can think of at the moment, but if anyone is interested PM me and I can direct to the best information source.

Need a big CU to fit all those DPCBs Mike