Light switch earthing
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Because, when you are a developer, with a site of 100's of new-builds, why would you spend that amount of extra time and money, when the IET guidance suggests it's unnecessary?
As I keep saying, it's not really as straightforward as that.
If earthing a back box would reduce risk in all situations, then what you say would clearly be correct. However, since there are some situations in which earthing the back box would increase risk, thought and judgement is really required.
Kind Regards, John
Well, if we complete 100 installations and we know from a fact that 51 people will do one thing and 49 people will do the other thing, we would cater for the 51 at the expense of the 49.
If we have a realistic expectation that nothing will change in that respect for the forseeable future then we might feel comfortable that we have done our best for them as a whole.
On the other hand, if we set a rule that we must cater for the 51`ers we might try to educate the 49`ers and reduce that 49 over time.
Of course, once we set a rule we should pretty well stick with it and hope that 51:49 split goes towards 90:10 eventually.
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Years ago, things were not as safe as they are these days and lots of folk took care accordingly.
Then we made things safer bit by bit over time.
Folk got acustomed to things being safer and took risks that the older folk would be risk averse to.
Result - we are now not much safer than we used to be.
RCDs are one example of folks taking greater risks than other folks used too. The design of lifts and liftshafts is another. Car designs another.
The list is endless.
If we have a realistic expectation that nothing will change in that respect for the forseeable future then we might feel comfortable that we have done our best for them as a whole.
On the other hand, if we set a rule that we must cater for the 51`ers we might try to educate the 49`ers and reduce that 49 over time.
Of course, once we set a rule we should pretty well stick with it and hope that 51:49 split goes towards 90:10 eventually.
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Years ago, things were not as safe as they are these days and lots of folk took care accordingly.
Then we made things safer bit by bit over time.
Folk got acustomed to things being safer and took risks that the older folk would be risk averse to.
Result - we are now not much safer than we used to be.
RCDs are one example of folks taking greater risks than other folks used too. The design of lifts and liftshafts is another. Car designs another.
The list is endless.
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"Years ago, things were not as safe as they are these days and lots of folk took care accordingly.
Then we made things safer bit by bit over time.
Folk got acustomed to things being safer and took risks that the older folk would be risk averse to.
Result - we are now not much safer than we used to be.
RCDs are one example of folks taking greater risks than other folks used too. The design of lifts and liftshafts is another. Car designs another.
The list is endless."
But in those halcyon days we were taught to use common sense and how to apply tolerance and discretion. All of which have been removed from the curiculum of life sciences.
Then we made things safer bit by bit over time.
Folk got acustomed to things being safer and took risks that the older folk would be risk averse to.
Result - we are now not much safer than we used to be.
RCDs are one example of folks taking greater risks than other folks used too. The design of lifts and liftshafts is another. Car designs another.
The list is endless."
But in those halcyon days we were taught to use common sense and how to apply tolerance and discretion. All of which have been removed from the curiculum of life sciences.
One obviously has to make a decision (and, if there are 'swings and roundabouts', has not option than to be "as comfortable as one can be" with that decision).
However, as your example illustrates, the swings and roundabouts may be fairly finely balanced. if, in your example, the 51 and 49 were reversed, then one would presumably come to the opposite conclusion - and one obviously cannot know with any confidenceee that 51% of people would do one thing.
Exactly - and I often remind people of that. I've actually heard people in my own family saying that they no longer have to drive 'as carefully', because of ABS.
Kind Regards, John
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Common sense has been replaced by 'rules and regulations' (which are often imperfect, and don't necessarily correspond with common sense) in many walks of life.
Kind Regards, John
The fact that the rules and regulations are "often imperfect, and don't necessarily correspond with common sense" is down to imperfect drafting of those rules/regs. That undoubtedly is, in part, due to "incompetence in charge" but, to be fair, it is probably never possible to produce totally 'comprehensive' rules.
The reason we have moved to "rules and regulations" is presumably essentially due to a changed attitude of 'us' to risk, probably at least partially driven by lawyers/litigation.
Of my grandmother's 11 siblings, five died before reaching adulthood - two of illnesses in childhood, two drowned (they lived near the sea) and one suffered some sort of trauma. However, that was essentially accepted as 'how it is' ('a fact of life/death'), without any thoughts of attributing 'blame', seeking some sort of recompense or taking steps to 'make sure it never happens again'. Today people think differently.
Kind Regards, John
And I am sure that the parents of the small children that died picking up loose threads under the cotton looms in the Industrial Revolution just accepted it as "a fact of life".
IMO, if someone has a financial incentive to not mitigate risks when providing a service, perhaps they should be held accountable.
Unless I'm missing something, isn't much of the confusion within this thread, due to the lack of specific 'rules' - leaving the interpretation of the 'guidance' down to common sense?
If there was a rule saying all metal back boxes should be earthed (via a flylead if the accessory has an earth terminal) - wouldn't we all be happier?
I don't think so.
There is no confusion; people have differing views.
No.
There is a specific rule: exposed-conductive-parts must be earthed.
Who thinks a back box is exposed?
Indeed - my point.
Maybe - but, as we are discussing, the matter of 'mitigating risks' may not be straightforward - particularly when, as I have been mentioning, a particular course of action may increase or decrease risk, depending upon circumstances/situation.
Kind Regards, John
As I've said, it's not necessarily possible to have a universally-accepted 'specific rules' - particularly when, as I have been discussing, a particular practice may either increase or decrease risk, according to circumstances.
In such cases, it's not even 'common sense', since it requires a judgement as to which of the 'circumstances' is the more likely - and, even then, it will mean that following the 'specific rule' would result in an increased risk in some circumstance's.
We might be 'happier' (maybe because our consciences could 'pass the buck' to that rule) but, as I've said, following that rule would result in an increase in risk of electric shock in some circumstances.
It's not a simple 'black and white'; world!
Kind Regards, John
There is.
For a start, as you have acknowledged, I don't think ther is any doubt that metal back box screws are 'exposed'.
However,as I've said, some people want to consider a situation in which a back box 'becomes exposed' because someone removes/loosens the screws and pulls the faceplate forwards (with circuit still energised) - but I agree that there is a definite limit to how far one can/should go in anticipating 'what people might do'.
Kind Regards, John
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