lollypop circuit

[JohnW2]

You have two things a lollipop and conductors in parallel. If either of the two 2.5mm² feeding the lollipop circuit have even a single socket then it's a figure of 8 and not permitted although I can't recall the rule it breaks only remember it was something we should test for.

We've discussed this before. A figure-of-eight is arguably theoretically 'safer' than a single ring, and I don't think you'll find any regulation which explicitly prohibits it. However, it can make testing a nightmare, particularly before one has worked out what one is dealing with!

Using two 2.5mm² in parallel is common for feed to grid switch in a kitchen which in turn as multi spurs ...

IME, it's not usually done quite like that, although the distinction may be a little pedantic If there are several grid switches the two arms of the ring usually go to the two end switches, with all the switches being 'daisy-chained' - hence a true ring, with spurs, not 'parallel cables'. Indeed, there are often other sockets in the ring, as well as the spurs supplied by the grid switches - so, again, in that case, definitely not 'parallel cables'.

I had a heated argument with my son also an electrical engineer about standard methods. I said it's down to the electrician to read the paperwork and to adapt his testing procedure to comply with the way wired however odd that system may be. He said to wire in a way any other electrician would not expect to find is wrong even if it complies with the regulations as future electricians may as a result make mistakes.

I'm with you on that one. For your son to say that something compliant can be 'wrong', simply because it is not common, is, IMO not appropriate.

Kind Regards, John

 

[Monkeh]

We must never do anything innovative or clever, we may confuse the younguns.

 

[deadshort]

We must never do anything innovative or clever, we may confuse the younguns.

We won't hold our breath then

DS

 

[JohnW2]

We must never do anything innovative or clever, we may confuse the younguns.

I'm not sure it's necessarily always going to be the younguns that are the problem. Some of those long in the tooth may be confused by, or not understand, things which have not been done "in the way wot we've always done 'em"!

The problem with many of the younger generation is, of course, that many of them have been taught in a "cook book" fashion, and don't have the background knowledge or understanding to be able to think about or understand anything which deviates by an inch from what is in the cook book (Appendix 15 of the regs perhaps being a case in point in this discussion ). However the solution is (should be) to educate them properly, rather than to 'ban' anything which is remotely unusual!

Kind Regards, John

 

[Monkeh]

I meant it figuratively, not literally. I AM one of the younguns - but not so easily confused!

 

[JohnW2]

I meant it figuratively, not literally. I AM one of the younguns - but not so easily confused!

Fair enough but, as I said, unfortunately a good few of the more recent recruits into the industry have 'enjoyed' the 'cook book' education, which leads to a lack of flexibility/adaptability (which requires background knowledge and understanding).

Kind Regards, John

 

[ericmark]

We all at some point take what we are told as being correct when we respect the teller for their superior knowledge. My old copy of "Book 3" tells me to test for figure of 8 and I accepted what it said as published by the IEE as it was then.

As I also said can't see what rule it breaches other than it could if too near the end of one leg cause an over load in the short leg.

If one expects something for example lighting circuits being as a radial when some one does something different like running a lighting circuit as a ring final because of volt drop one does not unless the plans are available even consider it may be a ring.

This was my sons argument where he said where every possible we should follow standard methods.

I have run two 150mm² cables instead of a single 240mm² simply as the 240 would not bend to radius required this is common with larger cables. But two 1.5mm² instead or one 2.5mm² is in theroy the same but in practice you would not expect to find it and 433.1.5 would seem to forbid it.

 

[JohnW2]

We all at some point take what we are told as being correct when we respect the teller for their superior knowledge. My old copy of "Book 3" tells me to test for figure of 8 and I accepted what it said as published by the IEE as it was then.

Indeed. I haven't actually checked but, for all I know, even present-day guidelines might tell one to test for a figure-of-8 - but, if we can't think of a reg that it breaches, I'm not sure what one is meant to do if one's testing detects such a circuit!

As I also said can't see what rule it breaches other than it could if too near the end of one leg cause an over load in the short leg.

I need to think about that one, and do some scribbling, but my intuition is telling me that that is not correct. Thinking aloud, if one starts with a ring with certain loads attached, if one joins two of the sockets (no matter where those sockets are on the ring) to create a figure-of-8 then (unless the situation is totally balanced, in which case no currents will change) I would have thought that the currents in the two legs of the ring would actually become more equal than they were - i.e. current will decrease in the leg which previously had the higher current, and increase in the leg which previously had the lower current. In other words, it would reduce the risk of overloading either leg. I'll think about it more, but is that not correct?

If one expects something for example lighting circuits being as a radial when some one does something different like running a lighting circuit as a ring final because of volt drop one does not unless the plans are available even consider it may be a ring. This was my sons argument where he said where every possible we should follow standard methods.

I understand his viewpoint. However, I think it fails because if we were always to assume that things had probably (or 'almost certainly') been done by standard methods, that would probably reduce our chances of detecting situations in which that was not the case. We need to 'expect the unexpected', and we would probably become complacent about that if the unexpected virtually never occurs.

Whatever, as I said, IMO it's ridiculous to have a situation (such as your son suggested) in which things can be reg-compliant but 'wrong'. If the authors of the regs regard non-standard methods as 'wrong', they should 'ban' them! If they don't do that, they are not 'wrong'!

Kind Regards, John

 

[kai]

Place a laminated diagram of any unusual circuit arrangements next to the main fuse box or consumer unit, highlighting any unusual situations for any future users or maintainers.

 

[ericmark]

I agree a circuit diagram is all that is required. And the regs do require them or some other means of identifying circuits.

As to the ring the new thinner cable 2.5mm² is smaller than the 7/0.029 cable that was used and the current ratting is lower we are told it must be 20A or over but using 106 meters of 20A cable if you were to start with a bank of sockets near to consumer unit then you could draw 26A from one leg and 6A from the other so over loading the cable.

One would hope near the consumer unit one would not fit an array of sockets but where some one has used a double socket box and extended the ring close to the consumer unit then the extra cable inserted will reduce the chance of overload at one end. However if it is figure of 8 then there is a good chance of overload.

Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying, capacity (Iz) of the cable is not less than 20 A and if. under the intended conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz) of the cable.

I suppose this means if you have a figure of 8 near either end then it will not comply.

In theroy one could connect a 4mm² cable to a ring final and spur off as many sockets as you wanted and if done around the centre of the ring it would not cause an overload on any cable.

However Appendix 12 does not show this as an option it seems to show every other option but does not show a lollipop, 4mm² spur or fig of 8.

I found a radial wired in 7/0.036 on a 30A fuse. In the third room however it had been split and 2.5mm² cable had been used for 6 extra sockets then it went back to 7/0.036 for 2 more rooms. It was in industrial premises so not a DIY job. Clearly the electrician thought he was working on a ring and clearly he did not test the work.

I swapped the 30A fuse for a 20A fuse. However had I connected the two 7/0.036 cables then I would have also removed the possibility of overload.

 

[JohnW2]

As to the ring ... we are told it must be 20A or over but using 106 meters of 20A cable if you were to start with a bank of sockets near to consumer unit then you could draw 26A from one leg and 6A from the other so over loading the cable.

I'm not sure what the 106m has got to do with it but, yes, we know that can happen with heavy loads near to one end of the ring. However, as you go on to quote, the designer is required to satisfy him/herself (as far as is possible) that such a situation in unlikely to occur "for long periods".

In fact (if my calculations are correct), with your example, a 26A load within 39.75m of one end of the ring would, in itself, result in a current >20A in that leg, even if there were no other loads on the circuit.

One would hope near the consumer unit one would not fit an array of sockets but where some one has used a double socket box and extended the ring close to the consumer unit then the extra cable inserted will reduce the chance of overload at one end. However if it is figure of 8 then there is a good chance of overload.

Although I haven't yet given deep thought to the matter, I still don't understand that. As I said, I would expect that converting a ring into a figure-of-8 would tend to make the current in the two legs of the ring more equal, thereby reducing current in what was previously the higher-current end of the ring. Put another way, the effect of adding the link to create a figure-of-8 is to make loads 'close to the end of the (sub) ring' actually 'further from the end of the (sub) ring' (in proportionate terms).

In theroy one could connect a 4mm² cable to a ring final and spur off as many sockets as you wanted and if done around the centre of the ring it would not cause an overload on any cable.

Indeed. That is not materially different from having multiple 2.5mm² spurs connected at, or very close to, the mid-point of the ring. Even if it were near to one end of the ring, it would be no worse than multiple 2.5mm² spurs connected to the ring in that vicinity.

However Appendix 12 does not show this as an option it seems to show every other option but does not show a lollipop, 4mm² spur or fig of 8.

You presumably mean Appendix 15. It clearly is not exhaustive, and is only a guide. Provided that the designer satisfies him/herself that "... the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying capacity (Iz) of the cable", there is no reason why they should not use designs which do not appear as examples in Appendix 15. For example, the designer might decide that it was appropriate to use 4mm² cable for the initial parts of the ring (at one or both ends), the rest being in 2.5mm² in order to satisfy the requirement.

Kind Regards, John

 

[scousespark]

Ericmark posted the following

To my mind the EICR should not have anything in it which does not breach a regulation or that is of a non permanent nature. Attaching an amendment which highlights areas of concern is OK but it to my mind should not appear in the main document. But the ESC takes a different view.

I also still consider anything permitted before BS7671 was added to the regulations name as not anything to do with any condition report today. We were at one time allowed knife switches but that was well before BS7671 started. So anything permitted before 1992 forget it. BS7671 did not exist then. Again the ESC takes a different view.

To my mind we have had three editions of BS7671, 1992, 2001 and 2008 and even to go back two editions is questionable with a PIR we looked at the previous edition so BS7671:2001 would still be considered as complying. It's stretching it to include BS7671:1992 but to include the 15th Edition and lighting without an earth to my mind is going too far.

Lets see is I have disturbed a hornets nest?

Read more: //www.diynot.com/diy/threads/lollypop-circuit.434493/#ixzz3aOZPlRd6

My response is

I read this and think it is saying that you would apply the regs at the time of installation. That's not correct, as you apply the regs in effect today. A non-RCD potected circuit will have been okay in 2003, but it's potentially a C3 today. if we started retrospectively applying regs, we'd have a nightmare of a job carrying out an inspection.

 

[scousespark]

Normally a lollipop circuit would be defined as a radial serving a ring.
If the the two 2.5mm2 cables in parallel are not loading any appliances on route, I suppose it could be considered a radial.

I would say this is a ring, by virtue of the fact that the end-to-end test shows continuity, even if the run is so short the reading is very low.

 

[JohnW2]

To my mind we have had three editions of BS7671, 1992, 2001 and 2008 and even to go back two editions is questionable with a PIR we looked at the previous edition so BS7671:2001 would still be considered as complying. It's stretching it to include BS7671:1992 but to include the 15th Edition and lighting without an earth to my mind is going too far. ... I read this and think it is saying that you would apply the regs at the time of installation. That's not correct, as you apply the regs in effect today. A non-RCD potected circuit will have been okay in 2003, but it's potentially a C3 today. if we started retrospectively applying regs, we'd have a nightmare of a job carrying out an inspection.

Good to see you. I think I agree with what you are saying, although I thought it was what people were doing, anyway. Does not something which is non-compliant with current regulations but which was compliant with the regs at the time of installation (no matter how recent/old those previous regs were) always deserve at least a C3?

Kind Regards, John

 

[JohnW2]

Normally a lollipop circuit would be defined as a radial serving a ring. If the the two 2.5mm2 cables in parallel are not loading any appliances on route, I suppose it could be considered a radial.

I would say this is a ring, by virtue of the fact that the end-to-end test shows continuity, even if the run is so short the reading is very low.

In the case described, I suppose that is strictly true - in the sense that any situation of parallel cables going from a CU to some point could be regarded as a ring. However, in relation to what I would call a 'true lollipop circuit', there would be a single, usually larger CSA, cable (rather than two parallel cables) from the CU to the origin of the main ring, in which case (as I said at the time), I think that PBoD's description as 'a radial serving a ring' would be essentially correct.

Kind Regards, John