Ring main.

[JKMRK1]

Question I have is, is it ok to have x2 ring main circuits on one 32amp type B MCB??

If so does this meet the current regs.

TIA.

 

[James]

I stayed in a Spanish rental for 2 weeks on holiday.
All the lightning circuits were just a single run of live, looped round all the switches.
The switched lives went off to there respective light pendants and instead of running a neutral to the fittings, they just connected the neutral of the fitting to the nearest bit of structural metalwork

 

[Mike Johnson]

Obviously the person who did that was wearing a Stetson.

 

[Pete999]

I stayed in a Spanish rental for 2 weeks on holiday.
All the lightning circuits were just a single run of live, looped round all the switches.
The switched lives went off to there respective light pendants and instead of running a neutral to the fittings, they just connected the neutral of the fitting to the nearest bit of structural metalwork

At what voltage?

 

[Mike Johnson]

As far as I know Spain is 220/230v @ 50htz.

 

[LastManOnline]

[ Citation required ]

Hi Guys. Just wanted to say I have read your replies so far with interest.This morning am a bit tied for time and want to give a reply to

Advantageous in what way?


Is this part of a move to closer alignment with EU wiring practice (similar to your T&E going for equal-size CPCs)?

Or any other specific reason(s) for the preference?

I am not aware of any moves to reduce use of rings in order to more closely harmonise with Europe (the increased size of the CPC in t&e was I understand). I think the appeal of the radial over the ring swung the balance. I personally find them simpler from an installation and testing point of view. The wiring saved in the omitted leg of the ring in many cases pays for the extra mcb. The customer now has 2 circuits of 20 amp rather than 1of 32. Radials not easily overloaded.
What's not to like?
[automerge]1596457633[/automerge]

Ok now you've got my dander up! Ring circuits will probably disappear eventually. But the reason is not some technical reason it is because of the dumbing down of the population in general. As regards the origins of the ring circuit it was maybe ahead of it's time ecologically as it was to save copper, ergo the natural environment. As you know I am an advocate of the ring circuit as per the other thread you referred to. Perhaps you are an agent provocateur insidiously dripping non reasons for getting rid of the ring circuit? It seems you don't like them with a vengeance. Which is a bit strange not to be dispassionate about a bit of wire and solely concentrate on the science and reasoning of each circuit type. Both have their merits and application, you just jolly well leave our ring circuits alone chappy.

Interestingly I was on a forum here locally for Irish sparks (cost me 50 euro) and tried to start a debate on some areas of Irish work practices which I felt (still do) could be upgraded. I pointed to the UK and basically said "they are ahead of the curve here, could we learn from that?" The reactions?? Take a guess. I think it's understandable we all get a little protective about our own regs and work practices.
One post kindly suggested I move to the UK.
I think to move forward its important to stand back and look objectively at the accepted norms whatever in whatever environment we are in and ask "is this still acceptable".
Now the ring circuit is in fact a very innovative wiring system which cleverly made use of limited resources getting the maximum out of the minimum of copper. In my view it still has a role to play but in a limited role. By the way my use of the word" dinosaur " was disrespectful and I did, nt intend that.
[automerge]1596457981[/automerge]

Does EU practice mandate that radial circuits run simply from point to point? If any branches are permitted then surely inspection and fault finding becomes less straightforward.

I ask this because I remember reading about some European countries where it was common to find radial circuits that branched off in many directions - sort of like a tree.

I have worked on radials in several countries and they all followed the same loop in, loop out system. To branch of off like a tree is not a system I have seen, but even if they did remember that a radial is never vulnerable to overloading in the way a ring is
[automerge]1596458310[/automerge]

I support and endorse the ring final circuit.

That's fine Risteard. Do you also still "support and endorse" the installation of a 4ft earth rod (as we are both required to install under Irish regs) but as has been demonstrated here on this forum by multiple sparks in multiple posts is actually less than useless?
[automerge]1596459002[/automerge]

As far as I know Spain is 220/230v @ 50htz.

The cotinent all tends to be somewhere between 220 and 240 at 50htz
[automerge]1596459227[/automerge]

I stayed in a Spanish rental for 2 weeks on holiday.
All the lightning circuits were just a single run of live, looped round all the switches.
The switched lives went off to there respective light pendants and instead of running a neutral to the fittings, they just connected the neutral of the fitting to the nearest bit of structural metalwork

That really surprises me. I also stayed in one last year and like you can't resist having a good look at the electrics. I don't open anything up but it looked top notch. Rcbo, s on every circuit too.
Obviously the light switch and inevitable socket in the bathroom but quite honestly I think we here (British Isles) have a, thing or 2,to learn from them here. Now as Mike said "dive for cover"
[automerge]1596459373[/automerge]

In line with EU practice, Dual pole MCB's and radial circuits will halve the time taken for inspections and fault finding.

Dives for cover.

You are spot on here in my view. Did you mean rcbo, s when you mentioned dual pole mcb, s?
[automerge]1596459736[/automerge]

Does EU practice mandate that radial circuits run simply from point to point? If any branches are permitted then surely inspection and fault finding becomes less straightforward.

I ask this because I remember reading about some European countries where it was common to find radial circuits that branched off in many directions - sort of like a tree.

If this "branches of a tree" system interferes in any way with the standard wiring method for a radial circuit, then yes, that would complicate faultfinding. However, while circumstances, might occasionally require a JB to be I stalled between to sockets to branch off for a third, this would be an exception rather than the rule in my exp.

 

[Mike Johnson]

Dual pole MCB's are just that, it would need an RCB as well for the row of MCB's, but you can use multiple RCBO's instead and not need the RCB.

 

[nicebutdim]

I have worked on radials in several countries and they all followed the same loop in, loop out system. To branch of off like a tree is not a system I have seen, but even if they did remember that a radial is never vulnerable to overloading in the way a ring is
[automerge]1596458310[/automerge]


If this "branches of a tree" system interferes in any way with the standard wiring method for a radial circuit, then yes, that would complicate faultfinding. However, while circumstances, might occasionally require a JB to be I stalled between to sockets to branch off for a third, this would be an exception rather than the rule in my exp.

I know little of the practices employed in other countries - in fact I have limited knowledge of UK practices and hoover up information where it is available - but had read threads that mentioned some fairly complex radial circuits. These may have been in very old properties and not the sort of circuit conventially installed, but the subject of easier inspection and testing was raised and I thought it a reasonable question to ask.

The radial/ring debate is something of a fascination for me and my untrained mind can see benefits and drawbacks to both. In general I tend to prefer the idea of radial circuits, but can also see instances where a ring seems the more practical option - one example would be a kitchen or utility room that houses multiple power hungry appliances. Even with the application of diversity there is a good chance of washer, dryer, dishwasher and kettle being used at once and potentially overloading a 20A radial, which I guess is why those rooms tend to be fed from a 32A breaker. Unless my understanding of BS 7671:2018 is flawed, a 32A radial, which is buried in plaster (or conduit in plaster) would need to be run in 6mm and not particularly convenient from the perspective of installation?

 

[Pete999]

I know little of the practices employed in other countries - in fact I have limited knowledge of UK practices and hoover up information where it is available - but had read threads that mentioned some fairly complex radial circuits. These may have been in very old properties and not the sort of circuit conventially installed, but the subject of easier inspection and testing was raised and I thought it a reasonable question to ask.

The radial/ring debate is something of a fascination for me and my untrained mind can see benefits and drawbacks to both. In general I tend to prefer the idea of radial circuits, but can also see instances where a ring seems the more practical option - one example would be a kitchen or utility room that houses multiple power hungry appliances. Even with the application of diversity there is a good chance of washer, dryer, dishwasher and kettle being used at once and potentially overloading a 20A radial, which I guess is why those rooms tend to be fed from a 32A breaker. Unless my understanding of BS 7671:2018 is flawed, a 32A radial, which is buried in plaster (or conduit in plaster) would need to be run in 6mm and not particularly convenient from the perspective of installation?

4MM2 MATE, ,

 

[davesparks]

4MM2 MATE, ,

That is the minimum size allowed but is still subject to calculation.
In a modern house where every void possible is stuffed full of insulation it is likely to affect the calculations and result in 6mm being required.

 

[nicebutdim]

4MM2 MATE, ,

That's what I'd always understood to be the case for a 32A radial, but checked the OSG while typing that previous post and it shows that 4mm would only be suitable when clipped direct - of course I may be reading this incorrectly or failing to take other factors into account...

I'm here to learn from better minds than mine and usually try to find answers from old threads, but sometimes a question arises that I can not reconcile on my own.
[automerge]1596480075[/automerge]

That is the minimum size allowed but is still subject to calculation.
In a modern house where every void possible is stuffed full of insulation it is likely to affect the calculations and result in 6mm being required.

Thanks for this clarification. I've been navigating my way through regulations for a while, but installation methods sometimes cause me to pause and this was one of those instances. The circuit I envisaged was buried an a wall where it dropped to outlets, but clipped direct in the ceiling void - in such instances does the lower rating count or the most prevalent installation method?

 

[davesparks]

Thanks for this clarification. I've been navigating my way through regulations for a while, but installation methods sometimes cause me to pause and this was one of those instances. The circuit I envisaged was buried an a wall where it dropped to outlets, but clipped direct in the ceiling void - in such instances does the lower rating count or the most prevalent installation method?

The most onerous set of conditions that the cable is exposed to is used for the calculations.

Don't forget you can't just read the current rating from the tables, they are intended to be used in conjunction with the rating factors.
Also note that the rating factors can increase as well as decrease the tabulated current carrying capacity.

 

[nicebutdim]

The most onerous set of conditions that the cable is exposed to is used for the calculations.

Don't forget you can't just read the current rating from the tables, they are intended to be used in conjunction with the rating factors.
Also note that the rating factors can increase as well as decrease the tabulated current carrying capacity.

That last sentence is something to bear in mind as I tend to look for limiting factors, rather than those which may improve a situation.

Really need to get started with C&G 2365 as I'm continually setting, and trying to answer, questions that I don't have sufficient understanding to properly resolve - often inspired by real world experiences posted on this forum.

 

[LastManOnline]

I know little of the practices employed in other countries - in fact I have limited knowledge of UK practices and hoover up information where it is available - but had read threads that mentioned some fairly complex radial circuits. These may have been in very old properties and not the sort of circuit conventially installed, but the subject of easier inspection and testing was raised and I thought it a reasonable question to ask.

The radial/ring debate is something of a fascination for me and my untrained mind can see benefits and drawbacks to both. In general I tend to prefer the idea of radial circuits, but can also see instances where a ring seems the more practical option - one example would be a kitchen or utility room that houses multiple power hungry appliances. Even with the application of diversity there is a good chance of washer, dryer, dishwasher and kettle being used at once and potentially overloading a 20A radial, which I guess is why those rooms tend to be fed from a 32A breaker. Unless my understanding of BS 7671:2018 is flawed, a 32A radial, which is buried in plaster (or conduit in plaster) would need to be run in 6mm and not particularly convenient from the perspective of installation?

The"radial /ring debate" is one you will only find discussed in the British Isles in my experience. The rest of the world appears to have drawn its own conclusions. My previous posts have made my own views clear. Seeing the advantages that each wiring method offers is really the way forward.

 

[davesparks]

That last sentence is something to bear in mind as I tend to look for limiting factors, rather than those which may improve a situation.

It's never made clear at college either, they always refer to the rating factors as de-rating factors when in fact they can go either way.

The CCC tables are for ambient temperature of 30C, usually ambient temperature is a bit less in the UK so the rating factor increases the tabulated value.

Further confusion can be had from the way a calculation is normally done, rating factors are usually applied to the nominal current rather than to the tabulated CCCs. This way when a de-rating factor is applied the nominal current is increased.

 

[LastManOnline]

That's what I'd always understood to be the case for a 32A radial, but checked the OSG while typing that previous post and it shows that 4mm would only be suitable when clipped direct - of course I may be reading this incorrectly or failing to take other factors into account...

I'm here to learn from better minds than mine and usually try to find answers from old threads, but sometimes a question arises that I can not reconcile on my own.
[automerge]1596480075[/automerge]


Thanks for this clarification. I've been navigating my way through regulations for a while, but installation methods sometimes cause me to pause and this was one of those instances. The circuit I envisaged was buried an a wall where it dropped to outlets, but clipped direct in the ceiling void - in such instances does the lower rating count or the most prevalent installation method?

Interesting post this because ....
1) Pete 999 is correct
2)you are correct, and
3)Davesparks is correct.

In reality, the rating factors as Davesparks says may go up or down. Then we need to factor in something not mentioned often enough in the regs (for my liking), "common sense". In reality the likely hood is that insulation in houses will become more used as time goes by. We have this year started to use 16 amp mcb, s as standard for general socket circuits to "future proof" current installation work.