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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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  • 0

    I wonder, if we vote, for or against AFDD, what kind of result might we get?

  • 0 in reply to ebee
    ebee said:
    I wonder, if we vote, for or against AFDD, what kind of result might we get?

    Isn't that sort of what already happened with cross-industry representation in the BSI committees responsible for BS 7671, who came to the consensus of what we have?

  • 0 in reply to gkenyon

    I don`t know Graham, some things seem to get a big thumbs down in to what I consider the popular vote but seem to make it in sometimes. Well it appears to me but I may well have a totally slanted view of such things and that is why I commented. I`ve seen more suggestions they have very limited safety effect, not much safety versus cost effectiveness but plenty of the "well I wouldn`t have them" sort of attitude. Mind you RCDs probably had a not very good press a few years ago but I am a fan of them.

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  • 0 in reply to gkenyon

    I don`t know Graham, some things seem to get a big thumbs down in to what I consider the popular vote but seem to make it in sometimes. Well it appears to me but I may well have a totally slanted view of such things and that is why I commented. I`ve seen more suggestions they have very limited safety effect, not much safety versus cost effectiveness but plenty of the "well I wouldn`t have them" sort of attitude. Mind you RCDs probably had a not very good press a few years ago but I am a fan of them.

Children
  • 0 in reply to ebee
    ebee said:
    Well it appears to me but I may well have a totally slanted view of such things and that is why I commented.

    I can completely understand that. I also understand the situation we've all found ourselves in, moaning that absolutely everything is sub-standard or doesn't work, because of the sheer number of problems we've had to fix.

    More importantly, though, I also value the points of view put forward.

    Not that I haven't (regularly) done it myself, but Engineers are a cynical bunch (at least about their own profession), and do moan about things "never being right". - there are, as I said, reasons for that. And I also understand that changes in BS 7671 provide yet another set of problems to fix one way or another.


    But to make decisions on what ought, or ought not, to be included in a standard, and to what degree, requires a number of different perspectives on an issue to be taken into account ... and also a little thinking outside the box.

    For example, with cable sizing, let-through energies etc., there's a huge difference in the perspective of someone working mainly on up-to-100 A domestic installations, vs different range of prospective fault currents, wider variety of circuit configurations, and larger premises, as well as larger loads, in some other installations. Hence, the contents on circuits in BS 7671 itself is far larger than the "here's your answer" (OK, "industry rules of thumb") in the tables in Section 7 of the OSG.

    ebee said:
    I`ve seen more suggestions they have very limited safety effect, not much safety versus cost effectiveness but plenty of the "well I wouldn`t have them" sort of attitude. Mind you RCDs probably had a not very good press a few years ago but I am a fan of them.

    Again, I fully appreciate that, and the point about RCDs is exactly that (and only that) which I was making.

  • 0 in reply to ebee

    A customer of mine had two adapter type Powerbreaker R.C.D.s I went to replace a faulty socket and as a matter of course I tested both Powerbreakers. Both failed to trip off. Fortunately the R.C.D. in the consumer unit worked perfectly.

    Lack of regular testing is often the main cause of failure to trip off when needed.

    Z.

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