Details of BS7671:2018 Amendment 1 are here.

If it cost £10 to prevent each death then it is £10 well spent.

Indeed, but that is not to be confused with spending £10 on each of 30 million households, to prevent a death in just one of them - this is why it is not worth adding RCDs  or ripping out plastic consumer units unless you are rewiring anyway.

Some dispassionate logic follows.

For quick sums, let us assume the treasury cost of a life is nearer £1million, then spending something more like 33p on each of 30 million households, per life saved nationally, over the expected life of the average such installation, would the correct threshold beyond which you are wasting resources.

So if we can save 10 lives a year nationally, and the average house is rewired every 30 years, (this is a high limit, lower nos reduce the monetary figures to follow) then there are potentially 300 lives to save or lose over the next 30 years, so £300 million to save spread over 30 million households, only then does each one get a tenner to spend on a cost effective safety measure.

Of course due to inflation, it may appear cheaper or more expensive to fix things next year, depending if life costs or part costs rise faster, but the ratiometric scaling idea still applies.


I'd be tempted to suggest in many cases we can save more lives with the same or less money from getting people to check for loose carpets on stairs, or checking their hot water temperatures.

 

mapj1:

that is not to be confused with spending £10 on each of 30 million households, to prevent a death in just one of them

That to some extent is my gripe. The amendment aims to deal with the risk in single phase installations, but not 3-phase ones.

mapj1:

Money should only be spent to save lives, here or elsewhere, when it is cost -effective to do so. Anything else is a netloss to society.

AJJewsbury:

That to some extent is my gripe. The amendment aims to deal with the risk in single phase installations, but not 3-phase ones.

Yes, the new device described in option (iv) - based on the L-N voltage going out of bounds - is only permitted for single phase installations. From what I gather that's not casting any aspersions on 3-phase systems, but an acknowledgement that the approach is basically flawed as it is possible to have a combination of 3-phase loads and a broken PEN such that a L-N voltage is still within 230V+/-10% but the PEN is way over 70V from true Earth. If you do have a 3-phase system (and can't compare voltage with an electrode) you're far better off using one of the approaches in option (iii) - i.e. comparing with an artificial N point generated from all three lines (see A722.4) as that's far more reliable. So basically the most flawed approach is only allowed where there's no better alternative.

lyledunn:

I think that if I was an EV manufacturer, I would be thinking that these bods in the U.K. are giving grief about the installation of charging points and I would set about building a vehicle that didn’t give a toss what the earthing system was. My guess is that most of 722 will end up superfluous as the problem will be solved by the car itself.