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AFDDs - when do they work?

alanblaby

I'm struggling to see the benefots of fitting AFDD's.

I've searched the web, but cannot find any compelling evidence that they actually help in safety.

 The Proffesional Journals all say they are a good thing, but with little content to show the data used to show they make a difference.

As we know, many fires are not caused by arcs, the build up of fluff in a tumble dryer is a typical example.

When I did my Social Housing work, I found many burnt out shower switches, along with washing machine sockets and occasional cooker switches that were totally burnt around the terminals, yet, in many cases would still work until the switch finally fell apart. Clearly some of these switches had been arcing, then had fused the cable to the terminal, others showed black terminals with only a small contact area, thus heating the terminals and causing the 'fishy' smell, which was quite typical.

Is there any evidence that AFDD's would stop these failures?

What about internal appliance faults?

Wasnt Grenfell started in a fridge? If so, would AFDD detect that fault?

And, what are appliance manufacturers doing to make their goods safer? From what I see, there are still thin tin plate terminals on cookers,and poor, loose spade terminals inside firdges and other appliances.They are made to be as cheap as possible, and it shows when you tighten up a terminal, and it bends the back plate as it is so thin.   

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    Interesting point of view - but I know there are contributors out there who would be offended at the suggestion that they are driven by those motives.

    Of course - and especially so with non-product standards (e.g. BS 7671) - where contributors are many and varied. I mean no offence to anyone.

    Nevertheless, it seems that many product standards committees are dominated by the likes of BEAMA and GAMBICA whose declared purposes include "Our insight and influence help our members to be more competitive by increasing their knowledge and impact. Together we remove barriers and maximise the market potential in our industry." (GAMBICA) and "UK trade association for manufacturers" (BEAMA).

    Neither am I saying that there's necessarily anything wrong with that - product standards primarily exist to provide a manageable abstraction to those that wish to specify the selection of such devices (i.e. they can write 'widget to BS whatever' rather than having to invent reams of specifications) - that's all good of itself.

    What I am trying to say though is that we should perhaps be careful not to attribute more weight to achieving compliance with a product standard than is really there. An AFDD to BS EN 62606 will detect and respond to arcs of the type described in that standard - that's all. It doesn't say that those arcs are necessarily representative of what will occur when electricity starts a fire in real life situations, or that the cost of such device is justified by the saving of lives or property, or that the selection of such a device would be the best way mitigating risks from arcing in any particular situation - such considerations simply aren't part of the standard.

    As an extreme example, I could probably find a standard to which snake oil could comply (BS 4475 perhaps) - but I'd argue that any implication that the snake oil should be considered effective for curing headaches, simply because it complies with a relevant standard, is going too far,

       - Andy.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    It doesn't say that those arcs are necessarily representative of what will occur when electricity starts a fire in real life situations, or that the cost of such device is justified by the saving of lives or property, or that the selection of such a device would be the best way mitigating risks from arcing in any particular situation - such considerations simply aren't part of the standard.

    Excellent point ... BUT my point is very clear - see point following next call-out.

    AJJewsbury said:
    As an extreme example, I could probably find a standard to which snake oil could comply (BS 4475 perhaps) - but I'd argue that any implication that the snake oil should be considered effective for curing headaches, simply because it complies with a relevant standard, is going too far,

    Works both ways. We see information on-line debating this without considering the conditions in the standard, or whether those conditions are actually right.

    Trying to start and arc and saying the AFDD did or didn't react to that arc is really a rabbit-hole.

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  • 0 in reply to AJJewsbury
    AJJewsbury said:
    It doesn't say that those arcs are necessarily representative of what will occur when electricity starts a fire in real life situations, or that the cost of such device is justified by the saving of lives or property, or that the selection of such a device would be the best way mitigating risks from arcing in any particular situation - such considerations simply aren't part of the standard.

    Excellent point ... BUT my point is very clear - see point following next call-out.

    AJJewsbury said:
    As an extreme example, I could probably find a standard to which snake oil could comply (BS 4475 perhaps) - but I'd argue that any implication that the snake oil should be considered effective for curing headaches, simply because it complies with a relevant standard, is going too far,

    Works both ways. We see information on-line debating this without considering the conditions in the standard, or whether those conditions are actually right.

    Trying to start and arc and saying the AFDD did or didn't react to that arc is really a rabbit-hole.

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