Ring final circuit vs Radial final circuit

[mandinga1975]

Hello all

I am sure there is an easy explanation but I am curious ...

Would be interested to know whether there is any major differences between the Ring final circuit and the Radial final circuit.

I am currently studying my NVQ 2330 level 2 and the only difference I can see from the wiring diagrams is that the phase, cpc and neutral go back to the consumer board with the Ring and doesn't with the Radial.

Is there something that the phase, cpc and neutral do when they are wired back to the consumer board on the Ring circuit?

If they don't then why is it used as it seems that it's just a waste of wiring!!

Cheers and apologies if it's something very simple (it's not explained very well in my course notes).

Mandinga

 

[simonatlondon]

Hello mandinga,

the point of a ring final circuit is to use a particular size cable to carry more current than it would if it was a radial circuit. This idea apparentley came about after the 2nd world war. To save on copper wires.

Now the maximum amount of current a 2.5mm T&E is 24 amps. If we are using 2 cables to go to each point of that circuit, then in theory, you can pull twice as much current. Its actually a little less, thats why we use a 32a mcb for a 2.5mm ring circuit not a 40a or 45a. Remember we must always protect the cable from exceeding its current carying capacity.

So 20a mcb for a 2.5mm radial and 32a mcb for a 2.5mm mcb.

Also because the circuit is a ring, the resistance of that circuit is half that of a radial (in theory) and therefore providing a lower r1 + r2.

Hope that helps mate. Sorry, not too great at wording things I want to say.

 

[simopesh]

Ring final circuit has virtually no voltage drop and it is mainly used in dwelling larger than 100 square meters. (If my memory serves me correctly)
However, if you use a 4.0mm twin and earth as radial the specs are almost the same as on a 2.5mm ring final circuit.

 

[hughesy]

a ring is also one of 2 instances in a domestic premises where diversity is allowed ie a a 2.5 protected by a 32a mcb the other is the 0.5 flex on a ceiling rose protected by whatever protects the lighting circuit ie 10a mcb this is allowed as the light bulb wont pull more current than allowed on a 0.75/0.5 2c flex from a ceiling rose.Hope ive not confused things not very good at using the right words.

 

[simopesh]

The radial's phase,cpc,neutral does go back to the consumer unit otherwise it would not work.

Its not a waste of wiring but a valid point on cost. Interesting to note wether 4mm radials would equate to the same cost as rings. AND alot less hassle and confusion.

4.0 mm twin ant earth cost twice as 2.5mm twin and earth. The trick is that you are using only half the length when building a radial with it and it is also quicker to build. Majority of my rewires in the last 6 years are done with 4.0mm radial - 32amp fuse. No faults found!

 

[sivoodoo]

2.5mm is easier to work with too

 

[JulesHurley]

I have done some research into this, and from distant memory, the english love of ring mains being able to supply 32A, is to enable us to use "two bar electric fires", just as our Gran had!

I am a strong beliver that the only area that needs 32A ring main is the kitchen / utility. I prefer to fit circuits for bedrooms etc as 16A radials. May need one or two more MCbs.

From memory, we are one of the only countries that still exist on using Ring mains.

 

[marshr02]

Totally agree with JulesHurley. There is however a lot of resistance to moving away from the ringmain cct. It was an excellent ecomomic solution after the war to design ccts that could be used for heating while using least copper. Now we would use radial on Economy7 if using electrical heating...

 

[sivoodoo]

...so, whats the negative aspects of a ring cct? Apart from more cable clips.

 

[marshr02]

- It's overkill in terms of cable runs, when a 32A cct not required i.e. bedroom. Sometimes the topography of a building can make a cable ring uneconomic, and the cable run stops being a ring, more like a doubled up loop.

- the ring can become broken, say due to intermittent connection. The cct is now dangerous, but the fault is not apparent. I wonder how many ring ccts are in this fault condition?

- this is a minor one, but maybe of increasing issue; in a radial cct with no borrowed neutrals etc the flow & return currents are alongside each other - in the ring there can be a large area between flow & return currents, hence increasing EMI interference within the home.


Don't get me wrong. The ring circuit can be an excellent solution in a true 'power' cct where the topology suits a ring cable run..

 

[mrloy99]

...so, whats the negative aspects of a ring cct? Apart from more cable clips.

Radials are easier to test,can tee off with less restrictions than on a ring,easier to wire,less cable(sorry these are all positive aspects of a radial,just turn that about)

 

[PhaseShift]

A ring circuit would be the equivalent of running conductors in parallel. If one conductor becomes open on one side, then more current must flow in the other wire. Seems like the potential exists for more current to flow on a wire that isn't rated for it. The circuit would appear to operate normally until it failed completely or catastrophically.

In the U.S, we aren't allowed to parallel conductors unless they are 1/0 or larger. I don't know what that translates to in mm^2. And when we do, they must be the same length, same material, same insulation, same size, and terminate in the same manner. This is usually only done for services, or large equipment in industrial applications.

 

[PhaseShift]

Strange coz flex has multiple strands for each conductor and in effect they are in paralel

By flex, do you mean stranded wire? If so, each strand is in intimate electrical contact with every other strand, forming effectively one conductor. I would say that a stranded conductor, and two insulated conductors in parallel, are different animals altogether.

 

[lawsonium]

Hello, first post on here for me

Sorry to hijack your post but it is related... Promise ;-)

This is a perfect thread for me. I have just bought my first house and I am really excited about doing most of the work myself.
I'm not a newcomer to DIY and have installed a few additions to several electrical installations since I was quite young.

I googled my first big question about my newly acquired house circuit just now which was Ring versus Radial circuits haha.

I have identified that my house has been wired in the last 10 - 15 years by the local authority before it was bought by the previous owners and they appear to have installed a radial setup.

I was thinking that this was probably insufficient if I wanted to expand the usage of the system (e.g. new sockets, lights, spurs to outhouses etc) but after reading this thread I am now thinking that the radial setup is actually better suited to increasing the installation.

What are everyone's thoughts on this and what limitations should I consider?

There is also an Economy 7 system installed which is also on a radial circuit. One of the things I'd like to do with this is run an extension from one of the storage heaters into the outhouse to run the washing machine after 12 midnight. What are your thoughts on this?

Kindest Regards,

Matt.

 

[Guest123]

Do you intend to notify local building control before you do any electrical work on your house???

Dont get me wrong I dont mind giving anyone a few pointers but technically your not allowed to do much more than change a plug without notifying these days.

As for spurring off an existing storage heater circuit - definately not!!!! those heaters use a lot of power which is why it's one circuit per heater.

 

[LukeScotty]

lawsonium, lenny theloon is intitled to his opinion, Im not saying he is right or wrong, but does share a valid point

 

[lawsonium]

Thanks for your replies...

Do you intend to notify local building control before you do any electrical work on your house???

Is it really necessary to notify them when you are simply wiring in a couple of lights in an outhouse? Surely the proliferation of kits for outside security lights etc etc in popular DIY stores flies in the face of this idea?

As for spurring off an existing storage heater circuit - definitely not!!!! those heaters use a lot of power which is why it's one circuit per heater.

Well, the property I have is ex local authority and subsequently has been wired and re-wired by the local authority.
There are three separate economy7 circuits in the house, two of them are just a single heater per circuit but the third has (or should I say had) two large storage heaters on it.
I have removed both heaters as they were either side of a wall I needed to put a doorway through. I now have a single circuit with nothing on it (i.e. not spurring off another appliance).

My question was/is, does anyone here think it is a good idea to run this, now unused economy7 circuit, to the outhouse laundry to run the washing machine/drier after 12 midnight?
Also, can you purchase some kind of automatic switch to switch over to economy7 on a timer basis for a fridge freezer?

Kindest Regards,

Matt.

 

[Guest123]

Thanks for your replies...



Is it really necessary to notify them when you are simply wiring in a couple of lights in an outhouse? Surely the proliferation of kits for outside security lights etc etc in popular DIY stores flies in the face of this idea?


quote]

Hey Matt.

Probably without knowing it you have hit upon the biggest problem with the whole part P thing since it began.

What you have said is absolutely bang on, how can anyone take part P seriously when all the DIY stores continue to sell electrical equipment to anyone but technically, depending on what your doing and where your doing it it's against the law!!!!!

I'm sure if you look through the forum you will find numerous threads on this very topic.

Anyhow if the circuit is unused I dont see a problem with extending it providing that you make sure the earthing is upto standard and all disconnection times are still met. Bear in mind that the circuit will only be "live" between 12 + 7am so it wouldn't really be practical for a fridge.

Also you would need to check the loading of the washing machine and the drier if they are to be used at the same time, to make sure you dont exceed the current carrying capacity of the cable used in that circuit.

Cheers.

 

[mrloy99]

Thanks for your replies...



Is it really necessary to notify them when you are simply wiring in a couple of lights in an outhouse? Surely the proliferation of kits for outside security lights etc etc in popular DIY stores flies in the face of this idea?




Well, the property I have is ex local authority and subsequently has been wired and re-wired by the local authority.
There are three separate economy7 circuits in the house, two of them are just a single heater per circuit but the third has (or should I say had) two large storage heaters on it.
I have removed both heaters as they were either side of a wall I needed to put a doorway through. I now have a single circuit with nothing on it (i.e. not spurring off another appliance).

My question was/is, does anyone here think it is a good idea to run this, now unused economy7 circuit, to the outhouse laundry to run the washing machine/drier after 12 midnight?
Also, can you purchase some kind of automatic switch to switch over to economy7 on a timer basis for a fridge freezer?

Kindest Regards,

Matt.

I don't know how technical you are but your fridgefreezer changeover could be performed with a simple relay,suitably rated and installed beside your consumer unit,if you have a dedicated circuit.

 

[lawsonium]

Hey Matt.

Probably without knowing it you have hit upon the biggest problem with the whole part P thing since it began.

What you have said is absolutely bang on, how can anyone take part P seriously when all the DIY stores continue to sell electrical equipment to anyone but technically, depending on what your doing and where your doing it it's against the law!!!!!

Hi Lenny, thanks for the input. I have to say I tend to get infuriated by all the red tape in the world. Over complicates things. Virtually everything is against the law these days or offends someone.

Anyhow if the circuit is unused I dont see a problem with extending it providing that you make sure the earthing is upto standard and all disconnection times are still met. Bear in mind that the circuit will only be "live" between 12 + 7am so it wouldn't really be practical for a fridge.

Also you would need to check the loading of the washing machine and the drier if they are to be used at the same time, to make sure you dont exceed the current carrying capacity of the cable used in that circuit.

I haven't calculated it yet but I can't see that a washing machine and a drier are going to out load two big storage heaters. I will check the values and cable ratings before I install though, thanks for the warning.

As for the fridge/freezer, I am hoping to implement some kind of relay as per mrloy99 has suggested to automatically switch the power over at the point of changeover.
I don't know exactly how this is to be acheived but I can imagine it is readily available.

I don't know how technical you are but your fridgefreezer changeover could be performed with a simple relay,suitably rated and installed beside your consumer unit,if you have a dedicated circuit.

Hi mrloy99, thanks for your reply. I am keen to know more about this relaying idea. I assumed there would be a device available for this very application as I can imagine it would be commonly required.
Is it better to run an E7 circuit AND a normal circuit to the laundry and have a switch/relay near the utilities or as you have said near the CU, which I am guessing would require using the same cabling to the laundry for both types of supply?

Kindest Regards,

Matt.

 

[mrloy99]

Hi Matt,Reference your changeover relay,I don't know of a device specifically for this application as such but this might be something you could get an electrician to do for you but basicly if you connect this at the consumer unit you won't have to install another circuit.Your relay should be available at major electrical wholesalers(suppliers to the trade).
You would require an 8 pin plug in relay and base and a suitable mounting enclosure with din rail.You have 2 normally closed contacts and 2 normally open contacts and 2 commons and a coil contact(known as A1 andA2).The 2 sets of contacts would enable double pole switching.You mentioned previously that you have now a spare E7 circuit.Whenever you apply power to your coil say whenever the E7 comes on the relay would change over from normal tarrif to off peak and thence out to your circuit.The connections are straight foreward.Pm me if you need more detail.

 

[lawsonium]

You would require an 8 pin plug in relay and base and a suitable mounting enclosure with din rail.You have 2 normally closed contacts and 2 normally open contacts and 2 commons and a coil contact(known as A1 andA2).The 2 sets of contacts would enable double pole switching.You mentioned previously that you have now a spare E7 circuit.Whenever you apply power to your coil say whenever the E7 comes on the relay would change over from normal tarrif to off peak and thence out to your circuit.

Hi mrloy99, this sounds perfect, just what I require. I will ask some local sparks if they fancy the job perhaps. Thanks for the offer to PM as well.

As for my standard socket/light radial circuit, what do I need to think about when extending these?
For example, I have a circuit with JUST a twin socket point, what should I be looking for if I wanted to extend this by adding another twin socket?

From what I have read on this site, it is as straight forward as wiring another spur and taking note not to exceed the cable loading.

Kindest Regards,

Matt.

 

[mrloy99]

The circuit could most likely be extended useing 2.5mm cable to your additional socket,then if you wanted to supply your lighting also from this circuit,the normal practice would be to install a switched fused spur unit,also fed with 2.5 cable,and then come out of your switched/fused spur unit with 1.5mm cable to your lights,protecting your cables with conduit or mini trunking as required. Of course you should also take heed of the previous posters comments,regarding notification and testing etc.You should also ensure that any sockets are supplied via 30ma rcd.The same would apply for your other altered circuits.ie fit 30ma rcd
on E7 board also.

 

[lawsonium]

Of course you should also take heed of the previous posters comments, regarding notification and testing etc.You should also ensure that any sockets are supplied via 30ma rcd.The same would apply for your other altered circuits.ie fit 30ma rcd
on E7 board also.

Of course, I don't intend to ignore the sensible warnings. I will be getting all works checked by an electrician.

All sockets are on 30ma rcd's so I would only be extending from these. With regards the lights I doubt I will be adding to the lighting circuit but if I do I will probably extend the existing circuit rather than spurring off the sockets.

There is only one CU on the system currently and I am only assuming at this point (haven't checked yet) that the spare E7 circuit is being fed from rcd's installed in the CU. What are the rating likely to be for storage heaters? Surely they must be at least 30ma's?

Another thing is that the CU is now full and I'm wondering if I should be thinking about replacing it with a newer, bigger one or if I should be getting the local board to install an isolation switch and feed a second CU from a split tail?

Any thoughts?

Regards,

Matt

 

[mrloy99]

sorry,didn't realize you had existing lights out there.
Not sure what set up you have there,if you only have one c.u.
The ones I've seen before have twne for ordinary tarriff and another for off peak.Maybe the whole lot is on a dual tarriff supply.You might be getting in over your head here,but I will go on.As far as I know and am sure the learn'd brothers will correct me,but I believe that any new work has to comply to 17th edd.So if you extend your "E7" circuit to become a socket,all sockets need 30ma protection. However if you change the consumer unit,protection to 30ma will be required on all circuits in bathroom and all circuits with cables buried in a wall at a depth of less than 50mm,which in effect normally means all circuits.A dual rcd system is commonly employed,with the object being that you are not left without SOME power in the house.For instance it has become normal practice to install upstairs lights and downstairs sockets on one rcd and downstairs lights and upstairs sockets on another rcd.It would also require that your main earth bonds are checked and upgraded as necessary at this time.
All circuits should then be tested and readings noted on appropriate form for submission to council who will then charge you their fee to have work inspected...If you could include a photo of your c.u and meter it might help.

 

[brs73]

one of the tutors at college told us that one of the reasons for a ring was that if one leg of the earth was broken/disconnected ,then you'still have an earth from the other leg of the ring.

err, this post shouldn't be here. i was quick replying to another thread!!??

many,many,many moons ago,one of the tutors at college told us that one of the reasons for a ring was that if one leg of the earth was broken/disconnected ,then you'still have an earth from the other leg of the ring.

 

[mrloy99]

one of the tutors at college told us that one of the reasons for a ring was that if one leg of the earth was broken/disconnected ,then you'still have an earth from the other leg of the ring.

err, this post shouldn't be here. i was quick replying to another thread!!??

many,many,many moons ago,one of the tutors at college told us that one of the reasons for a ring was that if one leg of the earth was broken/disconnected ,then you'still have an earth from the other leg of the ring.

Yes,and same for a neutral or a live!!---everything would apparantly "work" but,if the cable, say live,was broken at the consumer unit,your full load perhaps up to 32amp would have to flow through the 2.5mm cable,which isn't rated to carry this load,causing overheating and thus a possable fire risk where the rat has made its nest with the sawdust and debris from the electrician cutting his holes in the joists and forgetting to clean up.

 

[lawsonium]

Interestnig stuff mrloy99, I haven't spent much time studying the system, only a quick look around, I intend to get to this and really concentrate on what's what when I've finished more of the structural work.

sorry,didn't realize you had existing lights out there.
Not sure what set up you have there,if you only have one c.u.
The ones I've seen before have twne for ordinary tarriff and another for off peak.Maybe the whole lot is on a dual tarriff supply.

My first thought was that 2 CU's wuold be sensible but there isn't. I will take a picture tonight and put it up for yuo to have a look at. I'll try and describe as much of the systyem as I can too.

Thanks,

Matt.

 

[lawsonium]

Hi there,

Sorry it's taken me a few days to get this to you. Been very busy working on the house. Replacing lead pipes with plasic, fixing dodgy joints in clay waste pipes, getting the plastering done, sanding floodboards etc etc etc...

Here is a picture of my switch box, if you need me to enlarge anything or describe the wiring of anything, please let me know. Any comments about this setup and how to improve it will be greately appreciated.

Regards,

Matt.

 

[mrloy99]

Hi there,

Sorry it's taken me a few days to get this to you. Been very busy working on the house. Replacing lead pipes with plasic, fixing dodgy joints in clay waste pipes, getting the plastering done, sanding floodboards etc etc etc...

Here is a picture of my switch box, if you need me to enlarge anything or describe the wiring of anything, please let me know. Any comments about this setup and how to improve it will be greately appreciated.

Regards,

Matt.

Hello Matt,
I would suggest that you post this as I new thread starter as this is all getting a bit long winded and off topic.(but you should be bringing things up to 17th spec if you are doing major renovations at this time)

 

[kevster]

there was talk of the ring final circuit being done away with when the 17th edition was being drafted but nothing, maybe its on the cards for the near future, the rest of europe are on radials with DP breakers i believe

 

[lawsonium]

Hello Matt,
I would suggest that you post this as I new thread starter as this is all getting a bit long winded and off topic.(but you should be bringing things up to 17th spec if you are doing major renovations at this time)

True, I will do later today hopefully, thanks. (Sorry for hyjacking this thread )

Matt.

 

[jimwee79]

Jesus none of you came up with the most obvious answer. if you get a fault on a ring it is a lot harder to find than on a radial. I aint even gonna explain why unless somebody asks but it`s pretty simple if you just apply a little common sense.

 

[ian.settle1]

Jesus none of you came up with the most obvious answer. if you get a fault on a ring it is a lot harder to find than on a radial. I aint even gonna explain why unless somebody asks but it`s pretty simple if you just apply a little common sense.

Why? the only difference between them is the extra leg back to the board.

 

[jimwee79]

Think if you have a fault on a ring you still have 2 live ends to test and a lot of live skts. where as on a radial wherever ur break is all skts thereafter are dead.

 

[Tokyo Joe]

...so, whats the negative aspects of a ring cct? Apart from more cable clips.

Don't forget the aspect of.......... Diy ers... kitchen fitters etc ....... cocking up ring mains over the years
As I have seen on lots of occasions.......... Then try to solve it !..... at least it is really hard to cock up a radial
Ps I am A 4.00mm radial fan !!! ....... So much easier to work with ... forget the cost !!!

 

[Mac]

Don't forget the aspect of.......... Diy ers... kitchen fitters etc ....... cocking up ring mains over the years
As I have seen on lots of occasions.......... Then try to solve it !..... at least it is really hard to cock up a radial
Ps I am A 4.00mm radial fan !!! ....... So much easier to work with ... forget the cost !!!

I did post something a while back,can't find it at the mo.Do away with rings and just use 4mm radials.The way to go

 

[leekemp85]

If for example you were rewiring a house would you still use the same method with the 4mm radial (kitchen, down stairs and up stairs) for the power circuits or would there be more circuit ie one circuits per room

 

[Mac]

If for example you were rewiring a house would you still use the same method with the 4mm radial (kitchen, down stairs and up stairs) for the power circuits or would there be more circuit ie one circuits per room

Kitchen on it's own circuit,rest of downstairs and upstairs on it's own circuits.Upstairs and downstairs circuits literally use nothing.

 

[supertoad]

a 16 A radial is easier to test /run/and idiot proof for uncle bill the was an electrician for the years ago and diy using the home electrics books. most important it allows seperation of cks for customer conveniance in case of a fault, its basicly foolfroof, for plugs 2xrad + kitchen+lts is enough for av 3bed flat-most important-cant make a ring a hazard-cable run up to 30 m no problems

 

[Andy78]

Really ?

 

[Guest55]

holy freakin thread resurection !!!!!!!!!
lol.

 

[supertoad]

4mm rad ideal in gally kitchens where kitchen fitters/etc need all high load appliances on one leg of a 2.5 mm ring /or any other kitchen

 

[supertoad]

yes!!!!!

 

[supertoad]

yes! and the rest-potential disaster

 

[Toonlad]

Price of copper these days??

 

[Engineer54]

4mm rad ideal in gally kitchens where kitchen fitters/etc need all high load appliances on one leg of a 2.5 mm ring /or any other kitchen

That just smacks of bad design, than anything else!! Tell us what potential disaster your trying to sell us on??

 

[supertoad]

typical kitchen fitter design, one leg of ring ofted overloaded, if it looks flash ok, nevermind the electrics

 

[Engineer54]

typical kitchen fitter design, one leg of ring ofted overloaded, if it looks flash ok, nevermind the electrics

Well they aren't electricians are they!! So what's this potential disaster your on about??

 

[mrloy99]

RING ISSUES AGAIN...I'm sure I've said this before but not on this thread...Anyway.I had to do some work in a house,moving a socket for the tv amp or something.My apprentice was at the consumer unit switching off,then back on again,the mcbs one at a time coz nothing was labled at the consumer unit. But the socket tester's neon indicators failed to extinguish. My apprentice was also leaving me in the dark as he was switching off 6amp mcbs too.So we swopped,me at the board end and him at the socket.I switched all the mcbs off except one 32amp and it was still live,then I flicked the last one off too and he yelled down to me that,that was it.So I flicked everything back on except that last mcb,only to find when I'd got back to the socket that it was live again(the hard way)...swearing profusly at my"thick" apprentice,I made my way back down to the cu and knocked the other 32amp mcb off and the first one back on again,then back up to the attic again,the attic socket(still live?) just had one cable at it...a spur off the house ring..It took a wee while before it sunk in that in order to isolate this circuit it was necessary to operate two breakers and later found out the same applied to the kitchen ring too.....The two ring legs had been interconnected,outgoing house ring leg connected to return leg from kitchen,at the mcb and return house ring connected to outgoing kitchen leg.It was impossable to switch off any socket via a single mcb. Ever since that I've gone off rings...Pity someone wouldn't enlighten the designers and engineers who do the drawings for us to follow, of the HAZZARDS of(improperly tested) ring circuits.