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When is a spark an arc? OR - When is an arc a spark?

whjohnson
Just watched some chap on the E5 youtube channel visiting Eaton in Austria. Eaton AFDDs have been something of a subject of ridicule in youtubeland, with various respected electrical content providers demonstrating through various real-world means that they don't function. So, off this chap goes to Eaton's HQ in Vienna where they provide him with a aluminium case full of test kit, complete with the Eaton logo and fitted out with various Eaton devices inside.

One of the devices is the Eaton AFFDD which has famously failed to operate on numerous youtube video presentations.

Of course, it trips when tested with their own test kit. After all, no point in trying to sell something which isn't really needed unless you can demonstrate that it actually works, so Eaton helpfully provides the 'right' arc signature so that the device can trip on command in front of all those cynical doubters.


Apparently, all those heath robinson youtubers have been getting it wrong because they have unhelpfully been simulating real world arcing events which these devices won't actually pick up. You see, according to the 'experts' you need an arc instead of a spark to trip the device! What the hell is the difference?


Oh how I laughed! Is this how far they'll go to flog you some old tat you don't really need?

Just how many different arcs and sparks are there out there? Has anyone told David Attenborough of all these new species to explore?


Feel free to jump in!
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    Another question - in the event of a fire where arcing was determined (god knows how) as the cause, yet the device did not operate, who would be liable?

    Would a caveat from the manufacturer stating that "it was the wrong type of arc M'Lud" stand up in court?
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    whjohnson:

    Would a caveat from the manufacturer stating that "it was the wrong type of arc M'Lud" stand up in court?




    That caveat would not be needed; merely stating the device met all the relevant standards but these standards do not yet replicate all real world scenarios would suffice. Similarly the standard requiring their installation is valid in that it is better to trip on those faults that can be recognised rather than none. The person who picks up the bill is the poor consumer (or hopefully the insurers). Unfortunately, like the AFFDDs, we live in the real world.

    Alasdair

  • 0
    So, are you saying that the manufacturer's legal rep would be muttering something along the lines of "M'Lud, my client cannot be held responsible for the negligence of a customer who is not providing the 'right kind of arc' to our device".
  • 0
    No. What I am saying is that the manufacturers are selling a device that meets a specific standard which defines what arcing must be detectable. The manufacturer is not claiming that the device will protect against 100% of arc situations. As far as I can see the manufacturer can only be held liable if they are claiming something for their product that it doesn't do (e.g. detect all arc faults) or if they fail to meet the standard that it is supposed to meet.

    You asked a specific question (who would be liable?) and I have provided my opinion based on my experience that it would not be the manufacturer. I don't think it is particularly helpful to have a requirement to fit an AFDD which is not going to be of much help in most arcing situations, but is it better to have something that may help in some situations rather than nothing?
  • 0

    The discussion has gone off the subject with RCDs being brought into the conversation, they don’t offer protection against arcs.



    Depends on the type of arc. If it's a L-PE arc an RCD certainly will. Likewise an MCB/fuse will probably disconnect a L-N or L-L arc (eventually). It's the 'series' arcs that are harder to detect. But then if you put all your connections in earthed metal boxes, most problems will have a degree of arcing (or at least leakage) to PE as the insulation breaks down before things turn into a towering inferno - so perhaps AFDDs aren't the only possible solution.  Then there's resistive heating too - which allegedly seems to have been blamed for most CU fires (rather than arcing) - presumably AFDDs won't help with that either.


    So maybe if you're fearful of electrical problems starting fires you might be better considering conventional protection devices, earthed metal enclosures and 'Class I' wiring systems (steel conduit or metal armoured/sheathed cables) rather than AFDDs?


      - Andy.
  • 0
    Far too radical an idea Andy!

    After all, if we wnet down that route, what are they to do with all those warehouses full of useless AFDDs?
  • 0

    whjohnson:

    Far too radical an idea Andy!

    After all, if we wnet down that route, what are they to do with all those warehouses full of useless AFDDs?




    There will always be an European market for them.

    Do you think that the introduction of AFDDs is a knee jerk reaction by the LFB and that do the IET have ancestrial obligations to  the FB?

    Legh

  • 0

    whjohnson:

    So, are you saying that the manufacturer's legal rep would be muttering something along the lines of "M'Lud, my client cannot be held responsible for the negligence of a customer who is not providing the 'right kind of arc' to our device".




    I'd be interested to see JP's comments if he is reading this, but what would matter to your ordinary sparks is whether failing to fit AFDDs would lead to liability in negligence.


    Assuming that causation can be demonstrated (i.e. the AFDD would have opened before the arcing would have caused the damage) would the sparks have been in breach of his or her duty of care by failing to fit an AFDD contrary to BS 7671's recommendations? (421.1.7)

  • 0
    I don't know. Can you be held liable for not following a 'recommendation' rather then a regulatory requirement?

    If so, that could open up a whole different can of worms.
  • 0

    whjohnson:

    I don't know. Can you be held liable for not following a 'recommendation' rather then a regulatory requirement?

    If so, that could open up a whole different can of worms.




    If it is a statutory requirement, there could be a statutory penalty, which might even be a criminal one!


    As for liability in negligence, there has to be a breach of the duty of care. In establishing that, the Court will compare the action taken with whatever standard there may be. Perfection is not required, but a reasonable standard is.


    So is your PI insurance in date? ?

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