Mixed brand MCBs and EICR coding

[ban-all-sheds]

I don't care who generates, or 'shows me' the evidence. I am being asked to believe something, without any reason (other than 'blind faith') why I should. I don't care whether the evidence/facts comes from manufacturers, academia, independent organisations, government bdioes or wherever, but if you want me to believe it, you have to show me some evidence.

That's a reasonable position to take, even if it is one ignored on a daily basis by billions of people around the world.

But in the absence of such evidence you have to show me why the right thing to do is to ignore what the manufacturers of the equipment say, and why, consequentially, it might be right to ignore what the Wiring Regulations say.

Stillp keeps suggesting that there are 'facts' (which could include information relating to actually measurable problems), but will not or cannot tell me what they are.

Oh come on - it's quite clear that presently it is "cannot".

 

[JohnW2]

Although your second point again brings up the "you don't know" problem, so it seems to me that there is only one question, and it applies equally to domestic and non-domestic.

I don't really understand that. If the DB is not under the control of "ordinary persons" (or if the supply is >100A) there is no requirement for it to be a 'type-tested' CU. My point/question was that if there is a perceived 'potential danger' in using something which is not a 'type-tested CU' when it is under the control of 'ordinary persons', why does that potential danger cease to be a concern if it is under the control of people who are not "ordinary persons" (or if the supply is >100A)?

And I would code it FI. The investigation required would probably be beyond the scope of the inspection, and quite possibly outside the competence of the inspector.

I don't really understand why you would think that any 'investigation' would be required. If the DB were not under the control of "ordinary persons" and was populated by components/devices which were compliant with the relevant Standards, what exactly would you feel required 'investigation'?

Kind Regards, John

 

[SimonH2]

But in the absence of such evidence you have to show me why the right thing to do is to ignore what the manufacturers of the equipment say

Well to start with, they have a vested interest in users not pick-n-mixing. As someone pointed out, by periodically EOLing a range of breakers they get to sell a new CU a few years down the line instead of selling a few replacement/upgrade parts.
Therefore, what the manufacturer says must be treated with "a certain amount of scepticism" as to whether it came from the engineers who know what they are talking about, or the beancounters and marketers who don't.

, and why, consequentially, it might be right to ignore what the Wiring Regulations say.

Says the person who has previously stated that (in relation to a different bit of the regs) that some bits "must" be ignored as a matter of principle.

 

[JohnW2]

... but if you want me to believe it, you have to show me some evidence.

That's a reasonable position to take, even if it is one ignored on a daily basis by billions of people around the world.

It's interesting that many of the countless millions (probably billions) with appreciable religious faith nevertheless expect/demand that evidence-based approaches are exercised in relation to matters affecting their healthcare and countless other safety-critical (or even legal) issues.

Kind Regards, John

 

[ban-all-sheds]

I don't really understand that. If the DB is not under the control of "ordinary persons" (or if the supply is >100A) there is no requirement for it to be a 'type-tested' CU.

Did we not establish that type testing was required for any CU/DB no matter which standard applied to it?

My point/question was that if there is a perceived 'potential danger' in using something which is not a 'type-tested CU' when it is under the control of 'ordinary persons', why does that potential danger cease to be a concern if it is under the control of people who are not "ordinary persons" (or if the supply is >100A)?

I can't answer the supply size question (nor, I suspect could most "ordinary" electricians - did you see what I said above about something being quite possibly outside the competence of the inspector?).

As for whose control it is under, I could hazard a reasonable guess that maybe the expectation is that extraordinary persons would have the necessary expertise to implement a heterogeneous solution.

I don't really understand why you would think that any 'investigation' would be required.

FGS.

You have agreed that, generically, it is not known that mixing is guaranteed to be problem free. It is not known that devices will never fail to operate as required. It is not known that devices will never be damaged. What is known is that the makers say not to do it.

And yet you still ask why a situation advised against by the makers and which is not known to be safe should be looked into?

Words fail me.

 

[ban-all-sheds]

Well to start with, they have a vested interest in users not pick-n-mixing.

Maybe they do.

And maybe using the swings'n'roundabouts principle Hager would pick up as many sales for their devices to go into MEM boards as they would lose to MEM devices going into theirs.

As someone pointed out, by periodically EOLing a range of breakers they get to sell a new CU a few years down the line instead of selling a few replacement/upgrade parts.

Indeed, but that is not something which is unique to or even more prevalent in the CU industry.

Therefore, what the manufacturer says must be treated with "a certain amount of scepticism" as to whether it came from the engineers who know what they are talking about, or the beancounters and marketers who don't.

By all means be sceptical.

Can you show me where the regulations say that scepticism is a valid exemption?

Says the person who has previously stated that (in relation to a different bit of the regs) that some bits "must" be ignored as a matter of principle.

Please tell us which regulations or "bits" I've said that about. In doing so please note that you may not cite regulations or parts thereof which cannot be complied with because they are meaningless.

 

[JohnW2]

Did we not establish that type testing was required for any CU/DB no matter which standard applied to it?

Not that I am aware of, at least as far as what BS7671 requires. The BS7671 requirement for a DB to be a CU (defined by BS7671 as a type-tested DB) applies only to installations with a single-phase supply ≤100A under the control of "ordinary persons". What did you think had been established which is different from that?

I have a 3-phase supply (3 x 80A). Does that mean that, as far as BS7671 is concerned, I do not need to use "CUs" (type-tested DBs)?

As for whose control it is under, I could hazard a reasonable guess that maybe the expectation is that extraordinary persons would have the necessary expertise to implement a heterogeneous solution.

We're not talking about implementation/installation of a 'heterogenous' DB - but, rather, to being 'in control of' the installation over a protracted period of service. The suggestion appears to be that, with such a 'heterogenous' DB, there is potential danger due to the risk of a protective device not performing as intended if/when called on so to do (or otherwise to become damaged) at some point during its in-service life. That failure to perform satisfactorily would presumably occur unexpectedly, possible years or decades down the road from when the DB was installed - and I can't for the life of me see how the fact that the installation was under the control of "non-ordinary persons" (no matter how expert they may be) could in any way prevent or mitigate such a postulated occurrence - can you?

Kind Regards, John

 

[stillp]

Did we not establish that type testing was required for any CU/DB no matter which standard applied to it?

Not that I am aware of, at least as far as what BS7671 requires. The BS7671 requirement for a DB to be a CU (defined by BS7671 as a type-tested DB) applies only to installations with a single-phase supply ≤100A under the control of "ordinary persons". What did you think had been established which is different from that?

I can't speak for BAS, but I would expect any DB, including a CU, to be in conformity to the appropriate part of BS EN 61439, which would mean that it has to be type-tested. That would include your 3-phase 80A DB.

That failure to perform satisfactorily would presumably occur unexpectedly, possible years or decades down the road from when the DB was installed - and I can't for the life of me see how the fact that the installation was under the control of "non-ordinary persons" (no matter how expert they may be) could in any way prevent or mitigate such a postulated occurrence - can you?

Installations under the control of electrically skilled or electrically instructed persons need not be consumer units, presumably because those skilled or instructed persons will recognise an incipient fault and take remedial action, or perhaps because they are protected by the EAWR, or some other reason.

 

[stillp]

Yet you'd be happy to fit mixed manufacturer's MCBs in a CU in spite of professional instructions not to?

On the basis of what little information I am allowed to have, I would be very much happier to have mixed make MCBs in a CU than to have a CU full of same-make MCBs whose design and performance was so marginal that they would be "quite likely" to fail the required performance tests if moved into a different enclosure.

Kind Regards, John

So, you, who would no doubt claim to be a rational person, would prefer to use devices in a way contrary to good engineering practice and their manufacturers' instructions, than to use devices in the way recommended by the manufacturer but about which you have been warned that misusing them might lead to a change in their operating characteristics?
Does not compute Will Robinson!

 

[stillp]

Well to start with, they have a vested interest in users not pick-n-mixing.

Maybe they do.

And maybe using the swings'n'roundabouts principle Hager would pick up as many sales for their devices to go into MEM boards as they would lose to MEM devices going into theirs.

And they'd make more profit, since the sale price of fully-loaded CUs is often much less than that of the component parts.

 

[stillp]

As for 'misuse', you need to tell yourself about that - it was you who wrote:

It's quite likely that they will pass the tests in one manufacturer's enclosure and not in another.

... and I merely responded by pointing out that it would be a frighteningly marginal product that would fail the required performance tests simply because it had been housed in a different enclosure - and nothing is going to change my mind about that!

How irrational! Why would you even be surprised that anything would fail to perform within its specification when used in a way that the manufacturer has tols you it should not be used?

 

[stillp]

Life is full of risks, and only if they are quantified can one decide whether they warrant any 'avoiding action'.

Not true. Have you never come across ALARP?

I have indeed (all the time, in fact!) and the whole point of the "RP" ("reasonably practicable") part is that it involves, to quote the HSE, "weighing a risk against the trouble, time and money needed to control it.". If one has no handle on level of the risk (probability of the event occurring), one cannot undertake the risk-cost assessment which is fundamental to ALARP. If a potential risk has been identified, it is therefore crucial to quantify the level of that risk if one wishes to apply ALARP.

If the level of risk is already extremely small, then ALARP would take the view that the "trouble, time and money needed to control it" could not be justified. We all face the risk every day that a meteorite could come through our roof, but the level of that risk is so low that we (per ALARP) don't take action to reinforce our roofs against that risk.

A poor example, since there is no action that could be taken to mitigate against the risk of a meteorite impact. However, you are missing much of the point of ALARP. (strangely enough I was discussing this with a senior HSE official only last week). It starts from the premise that any risk that can be reduced, should be the subject of remedial action. In the case of possible risks arising from the installation of mixed devices in a CU, the remedial action is simple, easy to implement, and has very low cost, so it is perfectly practicable and it would be expected that such action (i.e. using only devices from the same manufacturer) would be implemented. There is absolutely no need to quantify the risk, even if such a thing were possible.

I don't care who generates, or 'shows me' the evidence. I am being asked to believe something, without any reason (other than 'blind faith') why I should. I don't care whether the evidence/facts comes from manufacturers, academia, independent organisations, government bdioes or wherever, but if you want me to believe it, you have to show me some evidence.

We all do that all the time. I take some medicines that are accompanied by certain safety warnings. I might not understand the science behind those warnings, but I don't expect the manufacturer to show me evidence to support them. I just accept that they probably know more about their products than I do, and obey the warnings.

 

[JohnW2]

So, you, who would no doubt claim to be a rational person, would prefer to use devices in a way contrary to good engineering practice and their manufacturers' instructions, than to use devices in the way recommended by the manufacturer but about which you have been warned that misusing them might lead to a change in their operating characteristics?

That's not quite what I said. I frankly find it very hard to believe what you have told me, but if it really is true that the design and/or manufacture of some of these products is so poor/marginal that they are "quite likely" to fail to perform satisfactorily if installed in a different box, then I would be extremely concerned about that. I would regard that as a very rational concern and much greater than my current concern about this other theoretical 'potential danger', for which no-one so far seems able to to provide me with any evidence.

Kind Regards, John

 

[stillp]

What do panel builders do, whenever they want to mount an MCB onto a din-rail in a bespoke panel they have built?? Do they restrict themselves as to using breakers from the same firm as the enclosure??

A good professional panel builder will design and verify the panel to an appropriate standard, such as 61439. The verification might well include type-testing. I don't know any that would mix makes of MCB in a single panel, but most would be happy with a different supplier for enclosures and protective devices.
OTOH there are cowboys who will sling anything together at the lowest possible cost, and irresponsible customers who will buy from them.

 

[JohnW2]

...I merely responded by pointing out that it would be a frighteningly marginal product that would fail the required performance tests simply because it had been housed in a different enclosure - and nothing is going to change my mind about that!

How irrational! Why would you even be surprised that anything would fail to perform within its specification when used in a way that the manufacturer has tols you it should not be used?

By applying common sense. I would have thought that even you would agree that a protective device that was "quite likely" to fail just because it had been moved from one box to another would be so marginal (in design and/or manufacture) that no thinking person could have any faith in its ability to reliably perform the protective function for which it was designed.

Kind Regards, John