what constitutes a new circuit?

[JohnW2]

For it to be a new circuit the MCB/Fuse/RCD or the slot where it is fitted must have not been used before....

That's not necessarily true - it can still be a new circuit if the "MCB/Fuse/RCBO or the slot where it its fitted" had previously been used for something else. A member of my family had that situation a year or two ago. She needed an extra ('new') circuit but had no spare ways in her CU. However, one way was being used just for smoke alarms. She had that moved onto a lighting circuit, thereby freeing up a way for the new circuit.

I don't think that most of us would usually have any difficulty in deciding whether or not a circuit originating from what I call the 'primary' CU was a 'new circuit'. The issue I've been discussing with BAS relates to the situation in which a second CU is fed from one of the ways in the first CU. The question then is that of whether final circuits originating from that downstream CU then count as 'new circuits' or not. We know that per the BS7671 definition of 'a circuit', they would be new circuits (just as would anything connected via a FCU), but what we don't know is what is the intention of the Building Regs as regards this (and hence notifiability).

Kind Regards, John

 

[ban-all-sheds]

That's where we differ. To me it makes no sense that a circuit is notifiable if it originates from an MCB or fuse within one sort of box but not notifiable if it originates from a fuse in another sort of box (assuming that both boxes get their supply from the same 'existing' circuit). I would be interested to know what makes you think that makes sense?

So you don't think that any new circuits should be notifiable?

What about the installation of a CU?

 

[ban-all-sheds]

I don't think that most of us would usually have any difficulty in deciding whether or not a circuit originating from what I call the 'primary' CU was a 'new circuit'. The issue I've been discussing with BAS relates to the situation in which a second CU is fed from one of the ways in the first CU.

Actually what you've been doing is failing to explain in what material way(s) a circuit (which you would have no difficulty in deciding if it was new if it came from a CU which was supplied directly from the meter tails, or from a switchfuse on those tails, or from an MCB/RCBO in a small enclosure on those tails) differs from a circuit from the same CU supplied from an MCB/RCBO in a large enclosure, and why you would suddenly have some difficulty in deciding whether or not is was a new one.

With reference to (c) and (d) below, what if the upstream CU in scenario (d) contained nothing but an MCB/RCBO supplying the other CU? No other devices, no other circuits supplied.

The only difference then between (c) and (d) would be the size of the plastic box containing the upstream device, so what material differences arise from that?

How large does the enclosure in scenario (c) have to be before you consider that it's now scenario (d)?

What happens at the transition between N modules and N+1 which makes a difference and means that you now have difficulties in deciding whether circuits from the CU being supplied from the device in the N+1 sized enclosure are new?

OK. ... So if we can put to one side for a moment the definition of "circuit" what is the material difference between the following:
(a)... A circuit originating at an MCB in a CU which is directly downstream of the service fuse.
(b)... A circuit originating at an MCB in a CU which is directly downstream of a switchfuse.
(c)... A circuit originating at an MCB in a CU which is directly downstream of an MCB or RCBO in a small enclosure containing nothing else and supplying nothing else.
(d)... A circuit originating at an MCB in a CU which is directly downstream of an RCBO or MCB in another CU.

I agree that there is not a lot of difference. Scenarios (a), (b) and (c) are certainly effectively identical - in all cases you are talking about a final circuit originating from an MCB/RCBO in what I would call a 'primary' CU.

How does such a final circuit differ materially from one originating at an MCB in a CU which is directly downstream of an RCBO or MCB in another CU?

How do these differences result in different parameters for circuit design, different testing or a different form of BS 7671 certification?

 

[ericmark]

I circuit is made when some item is switched on. In the main these are not new so you don't require to notify. However buy a new oil filled radiator and plug it in and you have formed a new circuit but not as part of the fixed installation so you don't need to notify.

So if you use that oil filled radiator in another 13A outlet you have modified the circuit not made a new one.

As I has said the phrase needs a definition other wise it's a load of nonsense. As soon as it was declared that a FCU did not require notifying it resulted in not following BS7671 definitions so we revert to the dictionary so fit a new immersion heater and that is clearly a new circuit even though we would consider it's not notifiable. The writers likely wrote the law with the whole idea of allowing the courts to decide.

Many of the laws seem rubbish when you read them. In the beginning it was written on a TV licence that it was required to have a device able to receive TV radio signals when I went to school that would be the aerial but painting aerial black and white did not mean you only needed a black and white licence.

Originally having a TV set required a licence even if not used, court cases have changed that and now you can own one it's only the using which requires a licence. It has also been modified to include recorders you don't need a TV set and today we don't look at what the licence says but at case law.

This is the same with Part P until some one is taken to court for installing a new circuit without notifying we can only guess. I have seen court cases where some one claims to be a scheme member and is not. And for dangerous work. But for a court case to be brought it would seem the property has to be rented the LABC do not seem interested in starting procedures against private owners. Once rented there are it would seem many laws which faulty installations fall foul of and it seems when there is a death it's the HSE who bring the case. Of the cases reported for bad workmanship it does not seem to be anything to do with Part P notifying.

With the Emma Shaw Case for example it was the wrong person being given the task of inspection and testing which was what resulted in fines being awarded.

I have said before I do not want to be in court making case law so I tend to play safe but until that case law is made then no one knows what a new circuit really is.

Maybe it was made like this with the whole idea that it would be unworkable as with the famous law on ground nuts.

 

[ban-all-sheds]

Try not to invent conspiracy theories to explain things which are far more likely to be down to sheer bl**dy incompetence.

 

[JohnW2]

That's where we differ. To me it makes no sense that a circuit is notifiable if it originates from an MCB or fuse within one sort of box but not notifiable if it originates from a fuse in another sort of box (assuming that both boxes get their supply from the same 'existing' circuit). I would be interested to know what makes you think that makes sense?

So you don't think that any new circuits should be notifiable? What about the installation of a CU?

It's not for you or I to say what should be notifiable. 'They ' have decided that they want 'new circuits' to be notifiable, and, in the absence of a satisfactory explanation from 'them', we are trying to guess what was their intent. I think we're agreed that they are not talking about everything which would constitute a 'new circuit' per BS7671 definition (since that would include FCU-supplied items, which we do not think was part of their intent) but, beyond that, we really have no idea.

In fact, the more I think about it, the more difficult it becomes for me to see what sensible 'rule' they could come up with in which you/we would not be able to find some seemingly silly 'loopholes', illogicalities or inconsistencies. If one were prepared to accept a maximum OPD In of 13A, one could 'simulate' a CU with a 'line of FCUs' and it would not be very logical for them to say that one approach created 'new circuits' but the other did not.

As we've seen, even trying to apply 'common sense' is not very easy/successful. Taking the garage example, I think the first thing one has to do is decide whether or not new wiring in the garage which originates at a new OPD within the garage should be notifiable. If the answer is 'yes', then I don't think there is any logical choice but to say that the wiring remains notifiable whether the garage OPD is in a CU enclosure or in an FCU - to do otherwise would be electrically irrational. If one does that, then (in terms of what we think of their intent) one has got to find a way of defining that situation which does not result in every FCU in the installation creating a 'circuit' whose installation would be notifiable - and I struggle to see how they could find words to do that. Mind you, if one did decide that (because it was acting as a 'quasi-CU') an FCU in the garage did create a 'new (notifiable' circuit') then one might again struggle to find a logical and consistent argument as to why all FCUs did not create 'new (notifiable) circuits'.

Kind Regards, John

 

[JohnW2]

Actually what you've been doing is failing to explain in what material way(s) a circuit (which you would have no difficulty in deciding if it was new if it came from a CU which was supplied directly from the meter tails, or from a switchfuse on those tails, or from an MCB/RCBO in a small enclosure on those tails) differs from a circuit from the same CU supplied from an MCB/RCBO in a large enclosure, and why you would suddenly have some difficulty in deciding whether or not is was a new one.

I realise that but, as I've just written, my problem is with finding a logical and consistent way of looking at things which does not result in any FCU creating a 'new' (hence notifiable) circuit.

It is, as I've just written, difficult to see any logic in saying that, say, one or two 6A or 10A MCBs in an enclosure would create (notifiable) 'new circuits', whereas one or two FCUs supplying the same wiring would not. Maybe our mistake is in trying to stick to our intuitive feeling that FCUs should not, in general, create (notifiable) 'new circuits'.

If things were to be such that all FCUs created notifiable new circuits, I suspect we would see a marked increase in the use of plugs and sockets, unless the rules tried to make that practice notifiable as well!

As I recently wrote, I can't really see a solution with is sensible, logical and consistent - can you?

Kind Regards, John

 

[ban-all-sheds]

I would say "Yes; mandate compliance with BS 7671 and make notifiable anything which needs an EIC."

Were it not for the fact that by its own definitions BS 7671 says that an MEIWC is not appropriate for the installation of a fused spur.

[ASIDE]

If anybody apart from us is still reading this, and they are registered with the IET forum, I'd be interested if they could post a topic there about the fact that the definition of "circuit" in BS 7671 clearly encompasses a fused spur, and equally clearly the heading on a MEIWC says "To be used only for minor electrical work which does not include the provision of a new circuit". Do the people there think that an EIC is required for a fused spur?

[/ASIDE]

 

[JohnW2]

I would say "Yes; mandate compliance with BS 7671 and make notifiable anything which needs an EIC."

Well, in terms of notifiability, that's effectively the same as what it says now, simply with addition of the invocation of the BS7671 definition of 'circuit' (hence 'new circuit'). However, as you go on to say ....

Were it not for the fact that by its own definitions BS 7671 says that an MEIWC is not appropriate for the installation of a fused spur.

Exactly - and, as I keep saying, that's the problem. ... The more I think about it, the more I realise that the illogicality/inconsistency which is causing most of this problem is probably the 'intuitive view' of you and I (and probably most others) that wiring connected via an FCU should not be notifiable.

Is our intuition just wrong - and is it therefore us who are being illogical? It does seem difficult to argue that a fuse in an FCU does not create a (new) 'circuit', whilst any sort of OPD (even a fuse) in an enclosure we choose to call "a CU" (or switch-fuse etc.) does create a (new) 'circuit', doesn't it?

If we want new wiring originating from an FCU to be non-notifiable, but any new wiring originating from an OPD in a box we choose to call "a CU" (or switch-fuse etc.) notifiable, we are probably asking for some (electrically) very illogical rules, aren't we?

Kind Regards, John

 

[EFLImpudence]

Are you remembering that the previous rules for notification -

Schedule 4,2 (c) (ii)adding socket outlets and fused spurs to an existing ring or radial circuit.

specifically exempted fused spurs from the need to notify.


Can it be feasible that the new rules which removed a lot of 'serious' work from notification would intentionally ADD fused spurs to the list?


Just for the record, I agree that a cable installed as a new fused spur IS a new circuit.
I had an argument with an annual assessor about this once because, if it is not, then the certificate doesn't make sense as the OPD is, say, 32A but the Zs can be, with a 3A fuse, up to 15.6Ω.

 

[JohnW2]

Are you remembering that the previous rules for notification - Schedule 4,2 (c) (ii)adding socket outlets and fused spurs to an existing ring or radial circuit. specifically exempted fused spurs from the need to notify.

Yes, we are remembering that - and BAS referred to it:

Which it used to, until they "improved" it.

Can it be feasible that the new rules which removed a lot of 'serious' work from notification would intentionally ADD fused spurs to the list?

Who knows - although it would seem very odd (alongside all the other 'relaxations'). BAS and I had been assuming that such was not their intent, but now I'm starting to wonder. As I've said, it would be difficult/illogical to create rules which rendered wiring originating from, say, a 10A fuse in an FCU non-notifiable but wiring originating from a 10A MCB (or even fuse) in an enclosure notifiable.

Just for the record, I agree that a cable installed as a new fused spur IS a new circuit. I had an argument with an annual assessor about this once because, if it is not, then the certificate doesn't make sense as the OPD is, say, 32A but the Zs can be, with a 3A fuse, up to 15.6Ω.

In an electrical sense, it probably has to be regarded as a separate circuit, for the reason you describe, but that doesn't necessarily tell us what (undefined) meaning of 'new circuit' the Building Regs had in mind as regards notifiability - that is a legal/bureaucratic question (which should have been dealt with by definitions and/or greater clarity), not an electrical one..

Mind you, even your argument goes a bit wrong in 'silly' situations - if, irrationally, one connected a 13A FCU to a circuit protected by, say, a B6, then you presumably would not have to regard the bit downstream of the FCU as a separate circuit which had to comply (Zs-wise) in relation to the 13A OPD, since it was actually protected by a 6A OPD!

Kind Regards, John

 

[EFLImpudence]

Mind you, even your argument goes a bit wrong in 'silly' situations - if, irrationally, one connected a 13A FCU to a circuit protected by, say, a B6, then you presumably would not have to regard the bit downstream of the FCU as a separate circuit which had to comply (Zs-wise) in relation to the 13A OPD, since it was actually protected by a 6A OPD!

Well, yes, but inserting needless accessories would lead to silly situations

What if ...?

 

[ban-all-sheds]

Maybe it would have helped if the Building Regulations had used the term "new final circuit"?

If you add a fused spur to a final circuit you are not creating a new final circuit, you are just extending an existing one.

 

[JohnW2]

Maybe it would have helped if the Building Regulations had used the term "new final circuit"?

If you add a fused spur to a final circuit you are not creating a new final circuit, you are just extending an existing one.

Again we are really down to (the absence of) definitions. If a 'final circuit' were defined as that part of a wiring system which was downstream of the most downstream OPD, then I suppose the bit beyond a new OPD (e.g. FCU) would become a 'new final circuit', wouldn't it?

Kind Regards, John

 

[ban-all-sheds]

Final circuit as per the BS 7671 definition.