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.

 

[pc1966]

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.

But (most of) the rest of the world does not use fused plugs. Hence the advantage of the ring in terms of high number of sockets and loading diversity from many appliances and a supply MCB well above what would safe for the appliance wiring alone don't really apply.

Testing is another long drawn debate as well. The ring final has its own peculiar test strategy as you have both ends to play with (and to verify), but doing so it often a more through test than easily done with a radial set. Also if the radial test is half the time (as Mike suggested) but you have 3 times the number of final circuits you don't gain much!

Both circuits have their places so I don't really get the anti-ring/radial intensity of feelings as usually it comes from not seeing where each is best used.
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In reality, the rating factors as Davesparks says may go up or down.

Just like investments. Usually down!

Obvious one that appears from time to time are 16mm tails on a 100A supply fuse - plenty good enough as they are well ventilated and not bunched in a common sheath so getting the heat out is not like most folk remember for 16mm SWA, etc.

 

[davesparks]

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.

There is no requirement to factor in 'common sense' in cable calculations.
Carry out the calculations correctly and you will get the correct size cable.
You can factor in known future changes, but you cannot factor in unknowns.

You cannot be 'future proof' as the future is unknown, you can only guess at what the future might be.

As for installing only 16A socket circuits, we'll, I suspect my opinion of that idea would get me banned.

 

[LastManOnline]

But (most of) the rest of the world does not use fused plugs. Hence the advantage of the ring in terms of high number of sockets and loading diversity from many appliances and a supply MCB well above what would safe for the appliance wiring alone don't really apply.

Testing is another long drawn debate as well. The ring final has its own peculiar test strategy as you have both ends to play with (and to verify), but doing so it often a more through test than easily done with a radial set. Also if the radial test is half the time (as Mike suggested) but you have 3 times the number of final circuits you don't gain much!

Both circuits have their places so I don't really get the anti-ring/radial intensity of feelings as usually it comes from not seeing where each is best used.
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Just like investments. Usually down!

Obvious one that appears from time to time are 16mm tails on a 100A supply fuse - plenty good enough as they are well ventilated and not bunched in a common sheath so getting the heat out is not like most folk remember for 16mm SWA, etc.

Firstly the "feelings of intensity" I personally don't have. And I hope by some of my language I have, nt inspired them. I actually joined this forum because of the quality of the posts. I noticed the tendency to back arguments up with hard facts and that is where I like to be.
One point I would like to make. The fused plugs are a direct consequence of the ring circuit with its 32 amp OCPD. The rest of the world does not need them and its very convenient that way.

Your comment on the 16mm tails is spot on. I agree comeplelty. I dare not use the phrase "common sense" again as davesparks won't get a wink of sleep?
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There is no requirement to factor in 'common sense' in cable calculations.
Carry out the calculations correctly and you will get the correct size cable.
You can factor in known future changes, but you cannot factor in unknowns.

You cannot be 'future proof' as the future is unknown, you can only guess at what the future might be.

As for installing only 16A socket circuits, we'll, I suspect my opinion of that idea would get me banned.

Regarding the statement, there is "no requirement to factor in common sense". Perhaps not in your world, but there certainly is in mine. You are entitled to your own opinion here dave but as, has oft been said, you not entitled to your own facts. New regulations and requirements tend to appear as individuals use common sense and insight rather than just "follow the regs". You have contributed some significant and educational posts on a number of topics, but the above is not one of your finest

 

[nicebutdim]

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.

Pete and Dave would apply rating factors and would likely have a decent amount of common sense, whereas I'm enquiring from the position of someone trying to increase their understanding.

One thing I don't get is the idea of 16A circuits being a means of future proofing - while appliances have (and will) become more efficient, it's also likely that they will continue to become more numerous in homes. Surely a better way of future proofing would be to continue to provide a 20A (or higher) supply to those sockets, but using installation methods that are compatible with the sort of insulation you envisage. Downrating the supply sounds more like keeping costs down than future proofing.

 

[davesparks]

Regarding the statement, there is "no requirement to factor in common sense". Perhaps not in your world, but there certainly is in mine. You are entitled to your own opinion here dave but as, has oft been said, you not entitled to your own facts. New regulations and requirements tend to appear as individuals use common sense and insight rather than just "follow the regs". You have contributed some significant and educational posts on a number of topics, but the above is not one of your finest

Please explain how you factor common sense in to the calculations then? How to you translate common sense in to a numerical value to be used in calculations?

I am fully in support of the use of common sense where needed, and mourn its demise. But I don't see how it factors in to a calculation. Unless you mean you just arbitrarily adjust the cable size without calculation?

 

[Mike Johnson]

France and Germany do not run washing machines, dish washers, tumble dryers, water heaters off a radial circuit, but on their own dedicated supply, lots of other appliances have their own dedicated supply as well, so the potential of overloading the socket supply is reduced.

 

[LastManOnline]

Pete and Dave would apply rating factors and would likely have a decent amount of common sense, whereas I'm enquiring from the position of someone trying to increase their understanding.

One thing I don't get is the idea of 16A circuits being a means of future proofing - while appliances have (and will) become more efficient, it's also likely that they will continue to become more numerous in homes. Surely a better way of future proofing would be to continue to provide a 20A (or higher) supply to those sockets, but using installation methods that are compatible with the sort of insulation you envisage. Downrating the supply sounds more like keeping costs down than future proofing.

Pete and dave are clearly scrupulous in their application of regs etc. End of. However, regs must always be seen as a minimum standard. If possible, it's best to be ahead of the curve rather than behind it..We decided to downgrade to a 16 amp mcb for a number reasons. One, as you mentioned appliances are becoming increasingly more efficient. Seven or 8 years ago we either ran a 6mm to the utility to allow washing machine and drier etc to run simultaneously or 2 x 2.5 t& e, depending on the rating of appliances. In the most recent kitchen we did, the entire load of W. M. and Drier was 3.3 KW. That trend will almost certainly continue. General sockets circuits are no longer used for electric heating like they used to be. Down rating the supply does, nt save us any money but it dies "future proof" the installation regarding the installation of more insulation (which is the norm here).
Your point about the increase of appliances, is a valid one. The solution is also simple.As standard we always run in an extra 2.5. to utility/kitchen. Future proofing.

 

[pc1966]

Firstly the "feelings of intensity" I personally don't have. And I hope by some of my language I have, nt inspired them. I actually joined this forum because of the quality of the posts. I noticed the tendency to back arguments up with hard facts and that is where I like to be.

My comment was not directed at you, just an observation about how often the ring/radial topic comes up and how divisive it appears to be.

One point I would like to make. The fused plugs are a direct consequence of the ring circuit with its 32 amp OCPD.

No, they were deliberately created together.

The UK used to have two common plugs, rated at 5A and 15A (and a further two uncommon at 2A and 30A) , each on a radial circuit. This is wasteful of wiring for a large number of plugs, and inevitably you will end up with the wrong one for your application.

So the IEE (as the IET was then) came up with a proposal post-WW2 to keep costs down, safety up, and allow a large number of sockets as they foresaw the growing need for electrical power.

Hence the idea of a "universal" plug for most applications, but with a selectable fuse rated for the appliance. Today you can get that easily in 3A, 5A and 13A but from suppliers like RS also 1A, 2A, 7A and 10A. With such a fuse you don't care (within reason) what the supplying feed is rated at, so the committee finally settled for a typical 30A fuse behind this (also ensuring total selectivity with a 13A fuse in the event of a fault).

Of course the modern 32A B-curve MCB fails on selectivity but that is a topic for another day (see many posts on garage/out-building supplies)!

The rest of the world does not need them and its very convenient that way.

It is convenient, but wasteful.

The lack of a fused plug means the appliance cable has to meet the disconnection ratings of the main supply. For a typical MCB in the 10-20A range the adiabatic limit requires 1mm cable. So even for a small power demand you are wasting copper simply to meet the supply characteristics instead of, say, 0.5mm and a 3A fuse.

And as you can't sensibly push this supply up due to the final flex issue, you might need several circuits instead of the one ring.

Yes, it works perfectly well and most EU countries, etc, are quite safe, but it is a waste of the Earth's resources in doing so!

 

[LastManOnline]

Please explain how you factor common sense in to the calculations then? How to you translate common sense in to a numerical value to be used in calculations?

I am fully in support of the use of common sense where needed, and mourn its demise. But I don't see how it factors in to a calculation. Unless you mean you just arbitrarily adjust the cable size without calculation?

That's is a question I would love to have an answer for but I don't. It's a great idea.. a numerical value for common sense. My last post to "nicebutdim" is perhaps an example of the application of common sense. I cannot supply a numerical value, but perhaps a definition "factoring in the likely direction of the society we live in". In mine the focus on improved insulation in the home is very clear. The implication for electrical circuits is thus also very clear. So what is the wisest course of action..... Hence the 16amp.socket circuit.
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France and Germany do not run washing machines, dish washers, tumble dryers, water heaters off a radial circuit, but on their own dedicated supply, lots of other appliances have their own dedicated supply as well, so the potential of overloading the socket supply is reduced.

Correct, strictly speaking it's recommended that any circuit over 1500 watt should be on its own circuit

 

[davesparks]

r. The implication for electrical circuits is thus also very clear. So what is the wisest course of action..... Hence the 16amp.socket circuit.

How is that the wisest course of action? Limiting socket circuits to 16A does not seem like a sensible plan.
If you had said you calculate cable size as if there was more insulation than there actually is I could understand it. But to make an arbitrary decision to put all socket circuits on 16A OCPDs seems daft to me.

What size cable do you use for the 16A socket circuits usually?

Do you make the circuits smaller and run more of them to compensate for the reduction in available current?

 

[LastManOnline]

My comment was not directed at you, just an observation about how often the ring/radial topic comes up and how divisive it appears to be.


No, they were deliberately created together.

The UK used to have two common plugs, rated at 5A and 15A (and a further two uncommon at 2A and 30A) , each on a radial circuit. This is wasteful of wiring for a large number of plugs, and inevitably you will end up with the wrong one for your application.

So the IEE (as the IET was then) came up with a proposal post-WW2 to keep costs down, safety up, and allow a large number of sockets as they foresaw the growing need for electrical power.

Hence the idea of a "universal" plug for most applications, but with a selectable fuse rated for the appliance. Today you can get that easily in 3A, 5A and 13A but from suppliers like RS also 1A, 2A, 7A and 10A. With such a fuse you don't care (within reason) what the supplying feed is rated at, so the committee finally settled for a typical 30A fuse behind this (also ensuring total selectivity with a 13A fuse in the event of a fault).

Of course the modern 32A B-curve MCB fails on selectivity but that is a topic for another day (see many posts on garage/out-building supplies)!


It is convenient, but wasteful.

The lack of a fused plug means the appliance cable has to meet the disconnection ratings of the main supply. For a typical MCB in the 10-20A range the adiabatic limit requires 1mm cable. So even for a small power demand you are wasting copper simply to meet the supply characteristics instead of, say, 0.5mm and a 3A fuse.

And as you can't sensibly push this supply up due to the final flex issue, you might need several circuits instead of the one ring.

Yes, it works perfectly well and most EU countries, etc, are quite safe, but it is a waste of the Earth's resources in doing so!

Yes, they were created together. But they belong together as they are interdependent.

 

[davesparks]

Your point about the increase of appliances, is a valid one. The solution is also simple.As standard we always run in an extra 2.5. to utility/kitchen. Future proofing.

What do you do with the extra 2.5?
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Yes, they were created together. But they belong together as they are interdependent.

They are not interdependent, the fused plug is not dependant on a ring circuit.

 

[LastManOnline]

My comment was not directed at you, just an observation about how often the ring/radial topic comes up and how divisive it appears to be.


No, they were deliberately created together.

The UK used to have two common plugs, rated at 5A and 15A (and a further two uncommon at 2A and 30A) , each on a radial circuit. This is wasteful of wiring for a large number of plugs, and inevitably you will end up with the wrong one for your application.

So the IEE (as the IET was then) came up with a proposal post-WW2 to keep costs down, safety up, and allow a large number of sockets as they foresaw the growing need for electrical power.

Hence the idea of a "universal" plug for most applications, but with a selectable fuse rated for the appliance. Today you can get that easily in 3A, 5A and 13A but from suppliers like RS also 1A, 2A, 7A and 10A. With such a fuse you don't care (within reason) what the supplying feed is rated at, so the committee finally settled for a typical 30A fuse behind this (also ensuring total selectivity with a 13A fuse in the event of a fault).

Of course the modern 32A B-curve MCB fails on selectivity but that is a topic for another day (see many posts on garage/out-building supplies)!


It is convenient, but wasteful.

The lack of a fused plug means the appliance cable has to meet the disconnection ratings of the main supply. For a typical MCB in the 10-20A range the adiabatic limit requires 1mm cable. So even for a small power demand you are wasting copper simply to meet the supply characteristics instead of, say, 0.5mm and a 3A fuse.

And as you can't sensibly push this supply up due to the final flex issue, you might need several circuits instead of the one ring.

Yes, it works perfectly well and most EU countries, etc, are quite safe, but it is a waste of the Earth's resources in doing so!

Pc1966. If you were to stand in a room of (for arguments sake) Dutch electricians and present your argument as you have to me they would listen to you, realised you knew exactly what you were talking about, respected your point of view re. waiting earth's resources etc but would not be "converted" to the ring circuit. They don't have fused outlets or fused plugtops and it really is more convenient that way. They are happy to pay a little more (as, you see it) for that convenience. If you worked in their system for a little while you would feel the same.
On the other hand if a Dutch spark came to the UK he would quickly realise that polarity at sockets is a "great idea". And the sockets switches etc are much more robust than he is used to. Swings and roundabouts
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What do you do with the extra 2.5?
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They are not interdependent, the fused plug is not dependant on a ring circuit.

The extra 2.5 we run in for, as "nicebutdim" said the likely possibility of increasing appliances in the future.

Interdependent was the wrong choice of word. I meant to imply that a fused plugtops was inevitable if you have a 32 amp breaker/fuse

 

[davesparks]

The extra 2.5 we run in for, as "nicebutdim" said the likely possibility of increasing appliances in the future.

But what do you actually do with it? Do you leave it unteeminated somewhere or what?

 

[pc1966]

@Edmond Noonan The UK's post-WW2 situation was unusual as so much reconstruction was needed and not that many places actually had electricity outside of major conurbations, and so changing systems in use was practical and advantageous at that point. No one now is going to change the plug/socket type in use due to the massive headache it would cause! (I remember it was still common to see the round-pin outlets in to the 70s)

So really the ring/radial debate is limited to the UK and countries with a shared electrical background where both types are possible.

I remember many years ago there was some discussion about the goal of an common EU-wide electrical socket. Which as you can see got nowhere. What was the most promising choice was the IEC "kettle" style of connector as it is polarised, in widespread use already, and available at 10A (but often only 5A!) so probably enough for the majority of applications.

But then you get in to the details of local fuse/switch or not, and even the issue of shutters. The IEE was not willing to have open sockets and other standard bodies were not bothered as they never had shutters to keep kids from poking stuff in, etc.