Ring Circuits and Current Carrying Capacity theory?

[ban-all-sheds]

You should not accuse people of lying without proof.

But then that's you all over, isn't it, as well as thinking that it is somehow the act of an intelligent and mature person, and of value to the forum, to post things with the intention of winding other people up.

Me, I consider that sort of thing very childish and pathetic.

 

[JohnW2]

I'm tempted to try this magic "Ignore" button above Ban All Sheds name .... I wonder out of all those thousands of posts you have made, how many were actually contributing to this forum in a positive way other than nit-picking what people say in order to make yourself feel good or whatever other motive you have.

This is another problem. As you imply, if his only contributions to the forum were 'negative' (as well as tedious and sometimes unacceptably unpleasant), then it would be very easy for the rest of us (and maybe also the forum's moderators) to decide how to deal with the situation. However, he is very knowledgeable, intelligent and quite capable of making very valuable contributions to discussions when he wants to. Apart from the 'amusement value' (the novelty of which wears off quite quickly), I imagine that's probably one of the reasons why many/most people continue to read his posts (or, at least, 'scan' them for sensible content). I do, however, worry about his effect of the image of the forum, particularly in the eyes of newcomers - who often disappear and never return once he shows his face.

Kind Regards, John.

 

[stillp]

particularly in the eyes of newcomers - who often disappear and never return once he shows his face.

What about the many who never return even without comments from BAS?

 

[JohnW2]

What about the many who never return even without comments from BAS?

Yes, of course there are some of them - quite possibly more than the ones I was mentioning. However, common sense suggests that it's inevitable that some of those who experience an 'unwelcoming' (or worse!) response to their forum debut will dissapear as a consequence. Whilst I wouldn't suggest that BAS has a monopoly on this, I cannot think of any other forum regulars who would come even close to him in their potential to have this effect. You may, of course, disagree.

Kind Regards, John.

 

[ban-all-sheds]

This is another problem. As you imply, if his only contributions to the forum were 'negative' (as well as tedious and sometimes unacceptably unpleasant), then it would be very easy for the rest of us (and maybe also the forum's moderators) to decide how to deal with the situation.

The problem, actually, is your inability, or refusal, to read what I write, and only what I write, and not start thinking "Hmm - I wonder what he really meant by that".

 

[Mrdjc]

We are all entitled to our own opinions, and we can choose to read or ignore whatever we like, I completely agree with that.

What I do not agree with however, is how you have completely derailed and attempted to undermine this thread by asking irrelevant questions, upon receiving answers to those questions you go out of your way to argue against those answers.

I say A you say B.

Yes I am a new member on this forum, it inspires me to see people helping each other in life giving tips and advise.

What I can not stand is people nit picking on "beginners" over terminology, or attempting to bully members off the forum by attempting to outsmart them with this kind of behaviour.

It doesn't contribute anything positive to the forum, and as mentioned causes people to think to themselves sod this, and never return.

Imagine the collective knowledge this place could have if you didn't try to one-over members constantly intimidating them off the forum.

I am British, but I am studying in Slovakia.

If you wish, we can continue this discussion and I'll answer all of your latest questions/observations/conclusions you have made, because quite frankly, they are completely wrong as you have misinterpreted my answers into what you think is wrong.

You asked for Ze values. I do not have Ze values, there is no current earth system implemented in the house, therefore I have not measured anything related to it.
You turned that into something completely different, in an attempt to make me look like an idiot who has no clue.

That kind of behaviour, is why I called you a smart arse.
Manipulating text and taking it out of context in order to make yourself "be right" over someone else.

 

[stillp]

What about the many who never return even without comments from BAS?

Yes, of course there are some of them - quite possibly more than the ones I was mentioning. However, common sense suggests that it's inevitable that some of those who experience an 'unwelcoming' (or worse!) response to their forum debut will dissapear as a consequence. Whilst I wouldn't suggest that BAS has a monopoly on this, I cannot think of any other forum regulars who would come even close to him in their potential to have this effect. You may, of course, disagree.

Kind Regards, John.

Unfortunately many of those who post a question on here are really asking for the forum's blessing for something they've already decided to do anyway, and then they get upset when they're told that either a) what they're trying to do is stupid and/or dangerous, or b) they're not competent (in the legal sense) to perform that work, or c) they clearly don't even have the necessary skill sets to do whatever it is. I suspect that many of those would either get upset, or disappear for ever, whatever the language used to tell them what they don't want to hear.
Whether BAS's choice of language drives people away I have no idea, but I must say I'm a little shocked sometimes at his choice of language.

 

[JohnW2]

Unfortunately many of those who post a question on here are really asking for the forum's blessing for something they've already decided to do anyway, and then they get upset when they're told that either a) what they're trying to do is stupid and/or dangerous, or b) they're not competent (in the legal sense) to perform that work, or c) they clearly don't even have the necessary skill sets to do whatever it is. I suspect that many of those would either get upset, or disappear for ever, whatever the language used to tell them what they don't want to hear.

No argument with any of that.

Whether BAS's choice of language drives people away I have no idea, but I must say I'm a little shocked sometimes at his choice of language.

I would think (hope) that most people are shocked by his language at times - but it's not really 'bad language' that I'm talking about.

Whilst I have completely agreed with what you said above, its' not really pertinent to what has happened in this thread. This thread did not start with someone "asking for the forum's blessing for something they've already decided to do anyway" - it was a question, followed by some discussion, about the theory underlying ring circuit design - yet it still resulted in an only-too-familar evolution and 'tirade'.

Kind Regards, John

 

[ban-all-sheds]

But the tirade didn't come from me.

It came from people who thought that I had some devious ulterior motives and/or hidden meanings in what I wrote. Apart from one (pretty obvious, IMO) use of sarcasm, what I wrote was, as always, straightforward, and to be read as written, not overlayed with other people's inventions.

I could, justifiably, complain, that the "only-too-familar evolution" is people doing just that.

You, I know, have not failed to notice that if I think someone is a t**t I'll tell them so. If I think they're ignorant or incompetent and should not be doing whatever it is they want to do I will say so in plain and unambiguous terms. If I think that they have behaved like an idiot I will point that out in a way which cannot be misunderstood. Yet you still seem to think that I feel the need to deliver coded messages.

And when it reaches the ridiculous stage where I am criticised for editing something I wrote because I thought "hmm - shouldn't have written that", and am accused of doing it to make other people look foolish I'm not going to give a **** what people think, so clearly flawed are their judgements.

 

[ban-all-sheds]

What I do not agree with however, is how you have completely derailed and attempted to undermine this thread by asking irrelevant questions,

Nothing was irrelevant - it all arose from questions you asked or statements you made.

upon receiving answers to those questions you go out of your way to argue against those answers.

No - I disagree if I think they are wrong.

I say A you say B.

Yes, if I think A is wrong and B is right.

Yes I am a new member on this forum, it inspires me to see people helping each other in life giving tips and advise.

And the first reply in this thread answered your two questions

"How does a ring circuit affect current carrying capacity? Would it be 2x 27A?"

"what kind of theory do you apply to calculating maximum current for a ring circuit?"

And I asked you if ring finals were allowed in Slovakia because that's a very important consideration to anyone in Slovakia considering installing them.

What I can not stand is people nit picking on "beginners" over terminology, or attempting to bully members off the forum by attempting to outsmart them with this kind of behaviour.

I did none of those things.

I don't care whether you called them spurs or branches - your analysis of what a radial circuit is was flawed, and your example of why there's something wrong with them was also flawed, as it ended up actually being a critcism of a circuit which was never right in the first place, and that can be true of a ring final as well as a radial. Yes you can add outlets to a radial and end up with too much load on it, but you can also do that (and it's easier to do it unwittingly) with a ring as well.

You made a proposal for a circuit design which I thought was flawed, so I told you so - you know, as in "giving tips and advice".

You asked for Ze values. I do not have Ze values, there is no current earth system implemented in the house, therefore I have not measured anything related to it.
You turned that into something completely different, in an attempt to make me look like an idiot who has no clue.

I didn't turn it into something completely different, for any reason.

You said, and you've just said it again, that because you don't have a separate earth in your house, i.e. because you have TN-C rather than TN-C-S, you've not measured Ze. Well, sorry, but that's nonsense - of course you can do that - Ze has nothing to do with what's in your house.

That kind of behaviour, is why I called you a smart a**e.
Manipulating text and taking it out of context in order to make yourself "be right" over someone else.

I didn't manipulate anything, or take anything out of context, for any reason.

 

[ericmark]

I know this will seem strange but first we must ask why do you want the current carrying capacity?

If you want to work out the load you can place on the circuit then there is a problem with power sharing. If you were to take a double socket with two kettles plugged in for this we will assume 26A and with your 50 meters of cable you were to place it one meter from one end then at 0.018 ohms per meter you have a 0.018 ohms and a 0.882 ohms resistors in parallel giving 0.01764 ohms. This will give a volt drop of 0.45864 volts using this to calculate current in each leg we get 25.48A and 0.52A and considering the normal max of 21A for 2.5mm cable reference method 100 then clearly one leg is overloaded.

However if you want to know the current carrying capacity in order to complete other calculations as for example correction for operating temperature (equation 6 page 258 in red book) then you simply add the two figures together.
Appendix 10 covers conductors in parallel and it is complex. From memory it refers to pastel’s triangle. Good bit of A level maths. May also involve imaginary numbers think that comes under further pure maths. Anyway I would not want to work it out. So in the main we hide behind the historical limits for a final ring.

Current carrying capacity is a problem as in the main we rely on the fact it will rarely hit the tripping current which is why any fixed appliance over 2kW should not be supplied from a ring main. We all realise the immersion heater which could run at maximum for hours on end is a problem. But any other fixed appliance oven, dishwasher, washing machine, or tumble drier will fall in the same category. Hence with modern house dedicated circuits are provided for these items normally supplied from a grid switch array. I have questioned many times the supply to this. I have seen where two 2.5mm cables are run in parallel to feed these as to use a 4mm cable will cause problems in terminating. But really this is not a ring circuit but just two cables in parallel which are equal length so really come under another set of rules. I have done the same with large generators using 2 x 150mm rather than one 240mm cable as 150mm is so much easier to work with.

The whole idea of our ring circuit is hinged around the fused plug. The reyrolle plugs had fuses built into the pins and were used a lot with 110v supplies there was also a similar type without fuses and a key cut so fused type will fit either type of socket but un-fused type will only fit fused socket. The 16A plug used in the rest of Europe would need local fused connection units next to each socket so not really a practical method.

I was always taught to consider a spur as a non-fuse protected cable with a fuse at it’s termination and a radial has the fuse at the origin. However it seems that has been now lost and the words seem to have merged to mean the same thing.

Although with long cable runs the ring circuit will reduce volt drop and has some advantages it is not really worth while without the British fused plug. On a 16A MCB I think we are allowed somewhere like 150 meters of cable in a single circuit. But we would normally work with a 32A MCB (B type) which would limit cable used to 106 meters mainly due to volt drop.

In the UK there are still electricians who do things because they have done it that way for years rather than working out what they are really doing. To change from standard is a problem even if it’s within the regulations. Cables running horizontal or splitting house side to side rather than top to bottom does not break the regulations but does cause problems when people assume rather than check. If I was to rewire my daughters flat in Turkey I may well use British 13A sockets. But it would still be on 16A radials I would not install a ring as local electricians would likely make a mistake.

 

[Mrdjc]

I apologise for jumping to rash conclusions about ulterior motives and you appearing to be a smart arse.

I am now starting to think you are one of these people who genuinely thinks that their word choice and vocabulary and method of conveying information is the way it is supposed to be done, and you know no better than the method you use.

9 out of 10 people I have dealt with in the past that have acted like this, turned out to be trolls who did it for no other reason than to try to make themselves look clever.

The issue regarding Ze isn't to do with it not being measurable
It is to do with the fact that I have not measured it, nor has there been any need for me to measure it. I do not require the value in order to pull the wire I will be using in a new circuit.

I am simply renovating a house and ripping out the old wiring as I go along, and creating new circuits which will all be properly connected to a CU and have their own OPD's fitted.

As far as my design being "flawed" I simply take a 2.5mm2 cable, and calculate the Maximum CCC for its location. I then "design" the circuit so that the maximum load of the circuit does not exceed the Maximum CCC. 20A at 230V is still 4.6KW. I'm not going to cap a circuit at say 10A if its capable of 20A without issues.

The cable's CCC is the determining factor in designing the circuits maximum permissible load.

You may not agree with that, but that's what is going to happen.

The comment about my radial circuit being a Spur on a spur on a spur and it being pants came from the fact that the existing circuit was exactly that. 50 year old wiring with parts added left right and center over time.

 

[Mrdjc]

Thanks for your reply Ericmark.

Since quite a few people seem to be bent on writing off ring circuits for various reasons, perhaps I should do the same in light of what I read on the other thread today.

Only problem is, from end to end I have approximately 40M of cable in one room. It is 2.5mm2.

I could simply disconnect one end and leave it terminated at the last socket, and feed the other socket from the CU.

Only problem is, the circuit would be limited to 3.6KW / 16A maximum.
This due to voltage drop, which would be 11.3V (4.9%)

This as opposed to 4.6KW/20A and a voltage drop of only 7.2V (3.1%) using it as a ring.

3.6KW should be more than sufficient, but for that extra 10M of cable from the first socket to the last socket, is it really worth it?

 

[ericmark]

Don't think I talked about Ze but as far as a circuit goes it needs protecting at a value that will protect the weakest link. So if you use a 16A socket then even if the cable can take 100A the fuse/MCB needs to be 16A.

The same applies to lights. If the ceiling rose is rated at 6A then even if cable rated at 16A then you need to use a 6A fuse/MCB.

One could use fused connection units at each socket to reduce the maximum to 16A but problem is buying them. In the UK only 13A are available so to limit to 16A would require a enclosure and a MCB at each socket. Not really a good idea.

I would agree having a radial with 5 sockets all 16A and all from a 16A MCB does seem a little daft but so does installing a MCB at every socket.

So in real terms to use a final ring also means using fused plugs. You could use a reyrolle plug which is fused to 15A but the problem is both lives are fused not just the line.

So really your idea may be good but unlikely you can buy what you need to do it so better wiring same as all the other locals do.

 

[ericmark]

Sorry just seen reply to me.

As I did say using a ring to reduce volt drop is grand but will still need fusing to 16A.