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Topic Title: NA for AFDDs?
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Created On: 10 July 2018 08:59 AM
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 12 July 2018 07:10 AM
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I believe that in the 80s the Department of Trade and Industry (dti) produced a small leaflet entitled "RCDs your questions answered." The sub headings were: What are RCDs? How do they work? Where are they needed? Are there different types of RCD? Which is the best type? How RCDs are fitted. How can I find out more?

This simple coloured leaflet was very useful and I remember that we would include one with job estimates to customers. Customers could see the benefits of an RCD, so many were installed, and these days most houses in the U.K. have an RCD in one form or another.

But with A.F.D.D.s I can see that selling them to the general unwashed will be an uphill struggle, and in the domestic market I feel that if one in 10,000 to 100,000 people buy one then that will be the norm. I conclude that it will be a hard sell, as people can see no immediate benefit at all in installing one, and the cost is high.

Z.
 12 July 2018 07:37 AM
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Just where do the Americans get their statistics from? This video claims that at the time of it being made more than 30,000 home fires are caused by arc faults each year. Scare the public to generate business eh?

http://www.youtube.com/watch?v=C-SBly_2bPQ

Z.
 12 July 2018 07:56 AM
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sparkingchip

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I do wonder if the IET ever have done any research on what the general public perception of them and the wiring regulations are?

Most people cannot tell you who writes the wiring regulations and if you mention new regulations having been introduced the response is usually a dismissive, well they are always changing them, type of reply.

Those at the IET probably know this from general conversations in their personal lives, but I do wonder if the IET have ever tried promote the wiring regulations and potential issues they try to resolve directly to the general public.
 12 July 2018 08:37 AM
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KFH

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Does anyone have knowledge about how well l they have gone down in Germany? Does any other country use them in conjunction with RCDs?

I feel fortunate that having retired I am not having to try and sell this to my customers. While I can see potential benefits I am still a bit sceptical about the benefits in a normal UK domestic situation utilising RCDs and T&E which would eliminate a number of the scenarios that AFDDS are meant to detect.

The only publicity I have read about them was in a trade magazine where a manufacturer misused the UK electrical fire stats to make it look as if AFDDs were essential to our safety.
 12 July 2018 09:04 AM
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AJJewsbury

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Clearly the test button is verifies the circuit breaker part, not the arc detection function.

Humm - maybe. I gather AFDDs contain what's basically a small computer. So in theory it would be possible for the T button to trigger the generation of a test waveform, injected just after whatever the current sensor is (coil, hall effect sensor or whatever) - which would then test the entire system other than the sensor itself; or I suppose even inject it into an extra coil wrapped around the normal sensor. I've no idea if they actually do that of course, but I don't think we have enough evidence to dismiss the possibility yet.

A suitable AFDD tester may be a old orange coloured Black and Decker sparky commutator electric drill from the local car boot sale.

One of the videos demonstrating an AFDD used what looked to be a very sparky drill to demonstrate 'normal loads' - the AFDD did not trip. It did trip with and simple spark gap arc though - both in series and parallel with the drill (I was quite impressed that it was able to distinguish a series fault arc in series with the motor brushes arc).

- Andy.
 12 July 2018 09:17 AM
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lyledunn

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My original post was not really about whether the devices work or not or whether they can be statistically or commercially justified. I was just mulling over the consideration that the AFDD "recommendation regulation" has been placed in our national standard for electrical installations and whether designers would feel somewhat compelled by the obvious prudence in complying with the intent of that standard.
Say you are designing a care home. BS7671 2018 recommends that AFDDs are considered. Why would it be reasonable for the designer to second guess the national standard? Is it not likely that they will seek to comply, reluctantly or otherwise?

-------------------------
Regards,

Lyle Dunn
 12 July 2018 09:23 AM
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Originally posted by: AJJewsbury

Clearly the test button is verifies the circuit breaker part, not the arc detection function.


Humm - maybe. I gather AFDDs contain what's basically a small computer. So in theory it would be possible for the T button to trigger the generation of a test waveform, injected just after whatever the current sensor is (coil, hall effect sensor or whatever) - which would then test the entire system other than the sensor itself; or I suppose even inject it into an extra coil wrapped around the normal sensor. I've no idea if they actually do that of course, but I don't think we have enough evidence to dismiss the possibility yet.



A suitable AFDD tester may be a old orange coloured Black and Decker sparky commutator electric drill from the local car boot sale.


One of the videos demonstrating an AFDD used what looked to be a very sparky drill to demonstrate 'normal loads' - the AFDD did not trip. It did trip with and simple spark gap arc though - both in series and parallel with the drill (I was quite impressed that it was able to distinguish a series fault arc in series with the motor brushes arc).



- Andy.


Yes it appears that the early generation arc fault circuit interrupters in the U.S. did suffer from nuisance tripping due to say commutator sparking, but the later models have had an improved circuit installed within them that is immune to such commutator sparking apparently.

Z.
 12 July 2018 02:25 PM
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burn

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Originally posted by: lyledunn

Say you are designing a care home. BS7671 2018 recommends that AFDDs are considered. Why would it be reasonable for the designer to second guess the national standard? Is it not likely that they will seek to comply, reluctantly or otherwise?


You are right I would comply. If the worst happened and there was a fatal fire I don't think I could stand in court and say I know better.

burn
IET » Wiring and the regulations » NA for AFDDs?

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