Mixed brand MCBs and EICR coding

[EFLImpudence]

However, what stillp is talking about is the theoretical possibility that differing products, which had not been tested together, might conceivably influence one another to an extent which was 'of consequence'.

Isn't that the crux of the matter?

If they have all been tested to the same standard then that is, surely, not the case.

 

[JohnW2]

However, what stillp is talking about is the theoretical possibility that differing products, which had not been tested together, might conceivably influence one another to an extent which was 'of consequence'.

Isn't that the crux of the matter? If they have all been tested to the same standard then that is, surely, not the case.

No. To address stillp's theoretical (at least, as far as my knowledge is concerned!) concerns, the particular combination of devices concerned would have had to have been tested.

Kind Regards, John

 

[ban-all-sheds]

Fair enough. It may appease the professional conscience of an inspector by making them feel that they have "exhibited the highest standards of professional responsibility and duty of care", but it would really be a pretty meaningless gesture.

On the contrary - it would mean a great deal wrt the duty of care held by the inspector, his legal obligations, what his insurers require him to do and to the transfer of liability for any losses which arise from a fault associated with the mixed devices in the DB.

As you say, "nobody really knows", and you have yourself admitted that very few people would be able or competent to undertake the required 'investigation' called for by your FI code. In other words, in practice no-one would be able to do anything about your FI code.

Also not the case. When the "duty holder" has been formally notified that he should engage an expert to investigate an aspect of the installation there are 3 things he could do:

1. Ignore the recommendation, and hope that he is never held to account for any bad consequences of that decision
2. Implement it
3. Just get the thing replaced if that would be more practicable than (2)

 

[JohnW2]

...but it would really be a pretty meaningless gesture.

On the contrary - it would mean a great deal wrt the duty of care held by the inspector, his legal obligations, what his insurers require him to do and to the transfer of liability for any losses which arise from a fault associated with the mixed devices in the DB.

Yep, it would also have 'CYA' value for the inspector but, in reality, would almost certainly achieve nothing in terms of electrical safety

In other words, in practice no-one would be able to do anything about your FI code.

Also not the case. When the "duty holder" has been formally notified that he should engage an expert to investigate an aspect of the installation there are 3 things he could do: ....[/quote]Indeed - but, in practice, I strongly suspect that in the vast majority of cases, that 'recommendation' would be 'ignored', not the least because it would be next-to-impossible to find a suitable expert to engage. IMO, the FI code is intended for situations in which further investigation (inspection/testing) of the installation is required, not when the issue has been fully identified but an academic opinion is required as to whether it requires any action. The inspector is expected to be competent to decide whether or not to "recommend improvement" (C3).

Kind Regards, John

 

[ban-all-sheds]

Yep, it would also have 'CYA' value for the inspector but, in reality, would almost certainly achieve nothing in terms of electrical safety

It would only achieve nothing if the responsible person decided to do nothing having been advised that he should do something.

Indeed - but, in practice, I strongly suspect that in the vast majority of cases, that 'recommendation' would be 'ignored', not the least because it would be next-to-impossible to find a suitable expert to engage.

That is indeed an option open to the responsible person. If he decides that he will do nothing about a recommendation in a report he has commissioned because it is easier than doing what was recommended then so be it.

IMO, the FI code is intended for situations in which further investigation (inspection/testing) of the installation is required, not when the issue has been fully identified but an academic opinion is required as to whether it requires any action.

You are entitled to have that opinion.

The inspector is expected to be competent to decide whether or not to "recommend improvement" (C3).

The inspector is expected to be competent to decide which code to allocate to each of the observations he makes.

Using the model EICR in BS 7671 he has 4 codes available to him.

C1
C2
C3
FI

You may not tell him which one he has to use, or which ones he may not use, for any of his observations.

 

[JohnW2]

IMO, the FI code is intended for situations in which further investigation (inspection/testing) of the installation is required, not when the issue has been fully identified but an academic opinion is required as to whether it requires any action.

You are entitled to have that opinion.

I suspect that I'm not alone in having that opinion, and certainly would be interested to hear the opinions of others.

Kind Regards, John

 

[stillp]

Even in central London, let alone other places, if you walk down any 'high street' I think you'd struggle to find any precautions against terrorist attacks

Perhaps, but you mentioned buildings, not streets. I have to check in and out of a number of buildings in London and elsewhere, one of the reasons being concern about possible terrorist attacks. You must lead sheltered life in leafy Bucks. There are also CCTV cameras in the streets of most towns and cities in the UK.

the satisfactory performance of an MCB is not dependent upon the presence (and nature) of other MCBs

Yes it is, of those other MCBs (and other devices) are in the immediate vicinity, as they would be in a CU.

Whether deliberately or not, you are still misunderstanding me - either that or your statement is ridiculous. You are surely not suggesting that the satisfactory performance of an MCB requires that there are other MCBs in the same enclosure?!!!!
[/QUOTE]What on earth leads you to imagine that? This whole discussion is about an assembly of MCBs and other devices, in an enclosure, the whole being referred to as a consumer unit. The performance of each of those MCBs will be affected by the presence of the others, hence the need for type-testing of the assembly, to ensure that the interaction of the MCBs on each other is not sufficient to cause any of them to fail to function within their specification.

 

[stillp]

As I said before, that could lead to ridiculous situations - like reinforcing our roofs in attempts to at least reduce the effects of impacts from very small micro-meteorites. We would all be taking anti-malarial tablets in the UK, just in case an infected mosquito manages to hitch a ride on an aircraft from an area where the disease is endemic (despite the airline's insecticide sprays!). More topically, most buildings, certainly non-domestic ones, are theoretically potentially at risk of terrorist attacks, but very few of them take any precautions to reduce that risk. ... etc. etc. etc.

We could, and if any of those vanishingly-small risks could be alleviated by precautionary measures that have vanishingly-small costs, we could and should take those precautionary measures.

 

[stillp]

However, what stillp is talking about is the theoretical possibility that differing products, which had not been tested together, might conceivably influence one another to an extent which was 'of consequence'.

No, what stillp is talking about is the fact that testing products together with similar products from different manufacturers has been demonstrated to cause unwanted effects on the performance of those products.

 

[JohnW2]

What on earth leads you to imagine that? This whole discussion is about an assembly of MCBs and other devices, in an enclosure, the whole being referred to as a consumer unit. The performance of each of those MCBs will be affected by the presence of the others, hence the need for type-testing of the assembly, to ensure that the interaction of the MCBs on each other is not sufficient to cause any of them to fail to function within their specification.

Yes, that's what "the discussion" is about, but it's not what my comments your are taking to task were about.

Ironically, this side-discussion arose because I supported you in relation to the automotive analogies that EFLI was proposing! I was merely pointing out to him that tyres and brake pads cannot be considered in isolation from one another, since they only perform satisfactorily in 'compatible sets of four'. A car with only one tyre or one pair of brake pads will not function satisfactorily, even if the component is compliant with all relevant Standards, whereas an MCB does not similarly depend upon 'another three compatible ones being present' in order to function
satisfactorily.

I have even (subsequently) further supported your view (about MCBs) by explaining to EFLI why what he was proposing would not satisfactorily address the concerns you have been talking about!

Kind Regards, John

 

[JohnW2]

No, what stillp is talking about is the fact that testing products together with similar products from different manufacturers has been demonstrated to cause unwanted effects on the performance of those products.

So you keep telling us - but I would hope that you don't expect me to have 'blind faith' in your unsupported assertions, any more than I would expect you to have 'blind faith' in anything I asserted without any supporting evidence!

Kind Regards, John

 

[JohnW2]

We could, and if any of those vanishingly-small risks could be alleviated by precautionary measures that have vanishingly-small costs, we could and should take those precautionary measures.

True - but, as I said, it's very unusual for any 'measures' to have 'vanishingly small cost'.

In the case of 'wrong make' MCBs, it's pretty unlikley that they arise 'deliberately', or 'for the hell of it'. The situation most often arises if a 'wrong make' device is all that is immediately available, in which case there would be time/trouble (hence finite cost) in obtaining a 'correct make' one - or, of course, the 'wrong make' one might sometimes be used because it is cheaper, hence an obvious additional cost in using a correct-make one. If the degree of risk of mixed-makes is sufficiently high to justify those costs, then fair enough - but, as you are well aware, I haven't a clue as to the magnitude of the risk, so cannot comment.

Kind Regards, John

 

[stillp]

I would suspect that the usual reason for mixing is ignorance (such as a belief that if they fit, they must be OK) and/or lower cost. However, MCBs are pretty cheap anyway, so the amount that can be saved is small. Perhaps not vanishingly small, but certainly small.

I haven't a clue as to the magnitude of the risk, so cannot comment.

Hasn't stopped you so far!

 

[JohnW2]

I haven't a clue as to the magnitude of the risk, so cannot comment.

Hasn't stopped you so far!

I may have voiced my suspicions, but I can't comment on whether the degree of risk justifies the (not zero, or even 'vanishingly small') cost without having some handle on the level of risk.

Kind Regards, John

 

[stillp]

Stop commenting then!