Mixed brand MCBs and EICR coding

[stillp]

I think you are confusing "risk" with something else. If analysis, theory, observation, or whatever shows that something can lead to the potential to cause harm, then there is a risk, whether that risk has ever been realised or not.

With respect, I think it is you that is confusing "risk" with something else (namely "hazard"). To quote again from the HSE ...
"‘A Hazard is a potential source of harm or adverse health effect on a person or persons’."
and ..
" Risk is the likelihood that a person may be harmed or suffers adverse health effects if exposed to a hazard."

.. from which it should be clear that you are talking about hazards (potential sources of harm) and that risk is a quantification of the probability of the hazard resulting in harm, which cannot be evaluated if consequences of the hazard have never been realised.

Kind Regards, John

The potential source of harm in this case is electricity, or more precisely the effects of electricity. There are many techniques for evaluating risk that do not depend on the consequences being realised. Otherwise we would need a nuclear power plant to fail before we could evaluate the control systems used to prevent such failure.

 

[stillp]

If a component - e.g. MCB - is subject to the same tests, to qualify as type tested, as another similar component, then surely they can be classed as the same in all relevant respects.

No! Why on earth should that be? They have to pass certain performance tests, and some tests on materials. That does not mean they are the same, although (taken as components) they might perform the same function, with the same degree of assurance.
Most cars have to pass the same type test. Does that mean they are all the same, or that their parts are interchangeable?

If the part is the same size (physically fits) and has passed the same required tests, for example a brake pad, then yes.

So, if the brake pads for a Smart happen to be the same size as those for a Bugatti Veyron, and both vehicles have passed their type tests, you would expect those brake pads to be interchangeable?

 

[JohnW2]

Sorry, very remiss of me. I should have said that it is likely that they will pass the tests when incorporated into one manufacturer's assembly but not when incorporated into another's.

Fair enough. I'm therefore not quite so 'disturbed'.

The term "quite likely", in the context of failure of a protective device, would imply to me (in the unlikely event of needing to quantify such a casual statement) a far lower probability than the 0,1 you suggest.

OK. As you say, it was a very casual statement, so I suppose I (wrongly) assumed that you were thinking of an 'everyday' interpretation - which I still think would probably be a probability of at least 0.1. However, I accept that 'thresholds for concern, varying considerably between different situations, so I wonder what sort of "quite likely" you actually had in mind - 1%, 0.1%, 0.01% or what?

Kind Regards, John

 

[stillp]

since they wrote that a domestic CU must "... incorporate components and protective devices specified by the manufacturer complying with BS EN 61439-3"

That reference to 61439 refers to the CU, not the components. Perhaps they should have added a comma after "consumer unit", and after "manufacturer".

Your suggestion would make some sense were it not for the fact that what I quoted was part of the alternative to the whole board being compliant with 61493-3. We seem, yet again, to be dealing with a less-than-ideally-worded regulation in BS7671!

Kind Regards, John

Yes, there seem to be two alternatives: conformity to 61439-3, or conformity to 61439-3! Perhaps you'll remember that when the next public consultation is in progress.

 

[JohnW2]

How would they know, in the case of a product manufactured in say the Far East?

You'd have to ask 'them' for details, but, in the case of medicinal products, the 'policing' is the same whether the manufacturing Facility is in the Far East or Milton Keynes. At the primary level, it is reliant on a fair bit of trust, in that it is based on manufacturers declaring any 'pertinent changes' and submitting regular analytical results, Certificates of Compliance, Release Certificates etc. in relation to each batch of product they produce - but, as you will tell me, any of that is subject to potential fraud/abuse. However, that is supplemented by both regular and random inspections of manufacturing facilities, and also by random analyses of products imported into the EU.

Kind Regards, John

 

[JohnW2]

Yes, there seem to be two alternatives: conformity to 61439-3, or conformity to 61439-3! Perhaps you'll remember that when the next public consultation is in progress.

Indeed so - I have added it to my list! Do you yet have any inkling as to when the next public consultation might happen - or, indeed, whether it will be in relation to a further Amendment or a new edition?

Kind Regards, John

 

[stillp]

How would I know, I'm retired!

 

[stillp]

that is supplemented by both regular and random inspections of manufacturing facilities, and also by random analyses of products imported into the EU

A shame we don't have similar levels of surveillance for electrical products.

 

[stillp]

I wonder what sort of "quite likely" you actually had in mind - 1%, 0.1%, 0.01% or what?

For now, let's pretend I just said "it is possible".

 

[JohnW2]

The potential source of harm in this case is electricity, or more precisely the effects of electricity. There are many techniques for evaluating risk that do not depend on the consequences being realised. Otherwise we would need a nuclear power plant to fail before we could evaluate the control systems used to prevent such failure.

That is true - but in such (relatively unusual) situations, one cannot 'evaluate risk' but, rather, has to make an estimate of risk based on theoretical considerations.

In the case of hazards which result in incredibly rare risks of very serious consequences (as in nuclear power plants), one has no option but to adopt such an 'estimation' approach, non-ideal though it is.

Kind Regards, John

 

[stillp]

This discussion has reminded me of one a while ago regarding departures from BS7671. I'd promised to discuss this with a QC, and have now done so, over a long and expensive dinner (he paid!). He confirmed that compliance with a standard requires compliance with all its normative provisions, and was of the opinion that departures from the standard could only relate to non-normative provisions, such as recommendations. I'm not sure that is the way that members of JPEL/64 see the matter.
He did say though that he'd be interested to see a judge's ruling on that issue, and his interpretation could be wrong!

 

[stillp]

The potential source of harm in this case is electricity, or more precisely the effects of electricity. There are many techniques for evaluating risk that do not depend on the consequences being realised. Otherwise we would need a nuclear power plant to fail before we could evaluate the control systems used to prevent such failure.

That is true - but in such (relatively unusual) situations, one cannot 'evaluate risk' but, rather, has to make an estimate of risk based on theoretical considerations.

In the case of hazards which result in incredibly rare risks of very serious consequences (as in nuclear power plants), one has no option but to adopt such an 'estimation' approach, non-ideal though it is.

Kind Regards, John

Machinery designers do it all the time. An absence of historical accident data is not to be taken as an indication of an absence of risk.

 

[JohnW2]

that is supplemented by both regular and random inspections of manufacturing facilities, and also by random analyses of products imported into the EU

A shame we don't have similar levels of surveillance for electrical products.

Quite so - something which is often said here. There's plenty of regulation and legislation already in place - what is seemingly lacking is the resourcing and/or inclination to undertake such surveillance of electrical (and other) products.

Kind Regards, John

 

[JohnW2]

deleted - pressed button prematurely!

 

[JohnW2]

He [a QC] confirmed that compliance with a standard requires compliance with all its normative provisions, and was of the opinion that departures from the standard could only relate to non-normative provisions, such as recommendations. ... He did say though that he'd be interested to see a judge's ruling on that issue, and his interpretation could be wrong!

We've had this discussion before. It's interesting to hear that learned opinion, but does it differ from what any of us would have said. AFAICS, if one wishes to claim "compliance with a Standard" one has no choice but to comply with all the normative provisions it contained.

The discussion we've had before is about claiming compliance with Part P by demonstrating compliance with some (probably nearly all) of the normative provisions of BS7671, but using some alternative means of demonstrating compliance (e.g. an argument from first principles) with Part P in relation to one or two things which are non-compliant with BS7671. I personally see nothing wrong with that, so long as one does not attempt to claim "compliance with (all of) BS7671". I would also imagine that Courts would very much favour that approach, since the alternative would be to argue every single bit of compliance with Part P by 'arguments from first principles', which could take months! If the authors of BS7671 have already done things (like establishing safe currents for cables of given CSAs and installation methods), there really is nothing to be gained by someone 're-inventing that wheel' from first principles for the benefit of a Court!

Kind Regards, John