EICR - please advise

[EFLImpudence]

Nope - but those obsessed with "what it actually says" might point out that it says nothing about being "a special dispensation" (although we 'all' know that it is) - since it merely says that BS1363 accessories may be supplied through a ring circuit protected by a 30/32A OPD

Yes, but the main point of that regulation is the 'undersized' conductors.

It obviously would not be compliant as a radial if it were wired in 2.5mm² cable with a 30/32A OPD - but, as you say, when the far end is connected back to the OPD, it becomes compliant by virtue of the "special dispensation"..

no, but it has a 15A OPD. That was the original query.
There is no need to tell the OP that it would be dangerous/non-compliant if it had this or that; it doesn't.

If one wanted to get technical, I suppose one could observe that if all the socket outlets were sufficiently near the middle of the ring, it would be possible to show that, say, a 2.5mm²/32A ring would be compliant with 433.1 even without that "special dispensation".

Not sure "get technical" is the right phrase.

 

[ban-all-sheds]

He never suggested it contravened any - in fact he emphatically stated that it does not.

Yes - sorry - my bad. Seems I repeatedly missed either the 'not' or the 'non-'.

 

[ban-all-sheds]

Nope - but those obsessed with "what it actually says" might point out that it says nothing about being "a special dispensation"

It doesn't use those words, but given that without 433.1.204 the traditional 2.5mm² 30/32A ring final would not be compliant with 433.1.1, and with it the circuit is compliant, then 433.1.204 is a dispensation.

If a ring complies with 433.1.1 directly, without needing to rely on the provisions of 433.1.204, then 433.1.204 is of no relevance.

It really is not a difficult concept to grasp.

 

[JohnW2]

It's certainly not a concept which any of us involved in this discussion find difficult to grasp, but I never cease to be amazed by how difficult some people seem to find it to 'grasp concepts'!

 

[JohnW2]

Yes, but the main point of that regulation is the 'undersized' conductors.

As I've just written, some people seem to have difficulty in 'grasping concepts', and that includes working out what the 'main point of a regulation' is.

However, to be fair on this occasion, there is nothing in the regulation which explicitly says anything about 'undersized' conductors. On the contrary, it says that the conductors must be at least 2.5mm² (unless MICC), so those of limited thinking ability might believe that the regulation is 'about' any ring with cable ≥2.5mm², and not realise that it really exists only for cables which are 2.5mm²!

Not sure "get technical" is the right phrase.

Maybe not - but, as I said, it's perfectly possible to design a 32A ring circuit which uses 2.5mm² cable which is compliant with 433.1 without having to invoke the 'special dispensation' of 433.1.204. Anyone who subsequently added sockets to the ring might, of course, then need to invoke that dispensation.

Whilst that might be 'academic', it does theoretically open the possibility of designing a 433.1-compliant ring circuit using (Method C) 1.5mm² T+E (which cannot enjoy the 'dispensation' of 433.1.204) with a 25A (or even probably 32A) OPD. However, in that case, someone who subsequently added sockets could end up with a non-compliant circuit, without any 'dispensation' to fall back on.

Kind Regards, John

 

[EFLImpudence]

Some people are not good a grasping the concept that we cannot, in a BS standard for example, cater for those of limited thinking ability.
Also, at the start of 433.1.204 is "Accessories to BS1363 may be supplied...". I suspect that those of limited thinking ability do not know what may really means.

Ignoring MICC, those of substantial thinking ability may have difficulty with a regulation which states that the minimum allowed CCC of conductors is 20A but the minimum allowed to be used are ones of 27A.
The fact is rings were designed with BS3036s in mind and are no longer logical with MCBs. There is so little between 27A and 32A, and not that much between 2.5mm² and 4mm² that the ring today is virtually unnecessary as it is regulated.

 

[JohnW2]

Ignoring MICC, those of substantial thinking ability may have difficulty with a regulation which states that the minimum allowed CCC of conductors is 20A but the minimum allowed to be used are ones of 27A.

That's not really true. 2.5mm² T+E does not necessarily have a CCC of 27A. As we know, it seems that Table 4D5 was deliberately 'tweaked' so that Method A (and Methods 100 and 102) 2.5mm² T+E would become eligible for the dispensation of 433.1.204!

The fact is rings were designed with BS3036s in mind and are no longer logical with MCBs. There is so little between 27A and 32A, and not that much between 2.5mm² and 4mm² that the ring today is virtually unnecessary as it is regulated.

I think that we, and a good few others, are agreed on that. I haven't done the sums, but I imagine that if the regs wanted today to 'take as big a risk/gamble' as was taken when they were first conceived, then they would probably now allow 2.5mm² rings with 40A (conceivably even 45A) MCBs ... and I can't see why they don't allow Method C 1.5mm² (T+E) rings with 32A MCBs, since that's no worse/different from Method A 2.5mm².

Kind Regards, John

 

[EFLImpudence]

That's not really true.

Yes, it is.

2.5mm² T+E does not necessarily have a CCC of 27A.

Yes, it does.

As we know, it seems that Table 4D5 was deliberately 'tweaked' so that Method A (and Methods 100 and 102) 2.5mm² T+E would become eligible for the dispensation of 433.1.204!

I believe that is so, but it does not detract from the fact that the regulations state a minimum CCC but don't allow the use of conductors with that CCC.
Cable derating applies whatever one does.

I think that we, and a good few others, are agreed on that. I haven't done the sums, but I imagine that if the regs wanted today to 'take as big a risk/gamble' as was taken when they were first conceived, then they would probably now allow 2.5mm² rings with 40A (conceivably even 45A) MCBs

They might (and could) but it is not necessary and there is no point.
Apart from the fact that no one's 32A ring in normal use seems to cause the MCB to trip, using 4mm² (which is much nicer than 2.5), two 32A circuits could be installed - or two 25A.
My 16A kitchen circuit hasn't tripped yet. Admittedly the kitchen is very small but the appliances are the same.

 

[JohnW2]

Yes, it does.

Eh? The "CCC" surely means "the CCC with the installation method used", not what it would be with Method C (or 'in free air', which is usually even higher).

When 433.1.204 requires a CCC of at least 20A, it surely means "with the the installation method employed"? That is, after all, seemingly why they tweaked 4D5 to get Method A 2.5mm² up to 20A, hence OK for the 'ring final dispensation'.

Kind Regards, John

 

[JohnW2]

I believe that is so, but it does not detract from the fact that the regulations state a minimum CCC but don't allow the use of conductors with that CCC.

As I said, I really don't understand why they don't allow 1.5mm² T+E rings on a 32A MCB - as I said, no different from a Method A 2.5mm² one, which they do allow.

The fact that they do allow 1.5mm² MICC is seemingly even more strange.

Kind Regards, John

 

[EFLImpudence]

Eh? The "CCC" surely means "the CCC with the installation method used", not what it would be with Method C (or 'in free air', which is usually even higher).

Oh, come on John. I know you like a discussion but thinking up instances where something might be different is irrelevant.
433.1.204 does not mention installation methods.
It says you must have a CCC of 20A and then says you can't use a cable that does.

When 433.1.204 requires a CCC of at least 20A, it surely means "with the the installation method employed"? That is, after all, seemingly why they tweaked 4D5 to get Method A 2.5mm² up to 20A, hence OK for the 'ring final dispensation'.

Of course it does but that is the same for any circuit.

It still does not justify demanding 2.5mm² when all method C.

 

[JohnW2]

Oh, come on John. I know you like a discussion but thinking up instances where something might be different is irrelevant. 433.1.204 does not mention installation methods. It says you must have a CCC of 20A and then says you can't use a cable that does.

I have agreed, more than once (including in my most recent post), that it makes no sense that it will not allow Method C 1.5mm² T+E - and, as I said, that they do allow 1.5mm² MICC (if CCC, as installed is at least 20A) is even more bizarre.

Kind Regards, John

 

[Adam_151]

As I said to EFLI, I hadn't thought about Type 1/2/3/4 ones. However, as I asked him, were they still being installed during rewires in the 80s? I've personally never seen or handled one.

Breakers to BS3871 persisted into the 90s, John, BS3871 was withdrawn in July 94, however equipment certificed to the standard before this date could be manufactured upto 99. 60898 was introduced in 91. I can't recall seeing any installations newer than 94 with BS3871* breakers, it would be normal for an installation from say '92 to have BS3871 breakers.

*Memshield 1 might be an exception?, they might have continued up until it was replaced with memshield 2 in '97, though you can now get 60898 breakers for them, sit down before you get a price on them though.....

.... but...

The switch to the renard series of ratings had been effected by most manufacturers prior to this, and an "16A type 2 BS3871" would not be uncommon in the early 90s. I'm not sure there was any requirement to switch the rating series tho... you can get 60898 to the old british ratings in some ranges: https://www.rbstarelectrical.co.uk/collections/crabtree/products/cra53-30 that is old stock but I don't think it was that long ago they stopped production. Note that it is a 60898 type C, but appears identical to the old 3871 type 2, one would generally conclude that as type two is IM between 4-7 x In and type C is 5-10 x In , that it is probably somewhere between 5 and 7 for that breaker and it has simply been re-certified to 60898. You can't readily tell the difference when fitted in a distribution board. So a 30A cerified as 60898 - C looks identicial to a 30A 3871 type 2, however the max zs is quite different.... So is that an original breaker from 1986 when the board was fitted, or was it changed twenty years later when the re-fit happened? or do we not care and are confident that they are all really type 2?

 

[JohnW2]

Breakers to BS3871 persisted into the 90s, John, BS3871 was withdrawn in July 94, however equipment certificed to the standard before this date could be manufactured upto 99. 60898 was introduced in 91. I can't recall seeing any installations newer than 94 with BS3871* breakers, it would be normal for an installation from say '92 to have BS3871 breakers.

Thanks for clarifying. I wasn't sure (hence I asked the question), but I thought that 3871s 'went' and 60898s 'came' a few years earlier than that.

One interesting thing that BAS recently reminded us is that BS3871 MCBs were/are, to the best of my knowledge, the only OPDs with a 'fusing factor' less than 1.45. However, I'm not sure that makes any difference since, although the lower I2 (for a given In) means that 433.1.1(iii) could be satisfied for a lower Iz cable than would be the case with a 60898, 433.1.1(ii) would not be satisfied unless the cable had at least the Iz that would be required for a 60898 [which I personally think is probably silly - but I may be wrong]

Kind Regards, John