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Derailed another thread with AFDDs, so I am starting this one. I will simply say that UK RCDs and MCBs provide arc fault protection as is. UL not only knows that, but extensively researched UK power systems in an effort to emulate the very same concept 40 years. One the simply fact (growing concern) that the US National Electrical Code does not prohibit a maximum earth fault loop impedance.
 
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Here is the theory that started it all in the US:



First few minutes of this video explain it. Remember, the US has nothing on loop impedance and some US circuit breakers did not even have a magnetic trip function 40 years ago where as breakers in Europe did.




The the thing is, these uncleared short circuits as a result of lacking earth fault loop impedance are being incorrectly called "arcs"
 
T

The Ghost

I have looked at your contributions regards RCD as AFDD and on the surface it seems a compelling argument that it is true that RCD are AFD devices. The technicalities presented certainly superficially are a revelation and indicate a massive fraud if it is true. I note the report is from the 1980s' and wonder if further work or research has been done on this to your knowledge. A cursory search reveals only info on AFDD info.
 
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And at 9:20 in the video, notice the extension cord being used in a deliberate attempt to elevate the loop impedance.
 
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I have looked at your contributions regards RCD as AFDD and on the surface it seems a compelling argument that it is true that RCD are AFD devices. The technicalities presented certainly superficially are a revelation and indicate a massive fraud if it is true. I note the report is from the 1980s' and wonder if further work or research has been done on this to your knowledge. A cursory search reveals only info on AFDD info.

Further work was extensively undertaken by UL both in cords and building wiring. Here is but one example:
 

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Lucien Nunes

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I don't have time now to get caught up in this debate, but one quick thought;

We have to be a careful comparing US 120V circuits with European 230V. I appreciate that many US buildings have a few 240V circuits too, but numerically the 120V circuit prevails. Some important parameters vary as the square of the voltage or current, so there can be a factor of four differentiating the behaviour of US and UK general purpose circuits. Series arcs also have noticeably different characteristics and form in different situations at 230V vs. 120V. When looking statistically at the causes of actual fires, as well as detail differences in electrical technique, such as the kind of conduit used (or not), one has to allow for differences in building construction, climate and other external factors that affect how a particular electrical event relates to a fire outcome.

It is a complex subject and for the fireside observer, personal opinions about 'fraud' and 'rip-offs' are likely to heavily bias the view of what little technical information is available from controlled studies.
 
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Eventually US manufacturers lowered or added magnetic trip to around 10x the handle rating.





The first AFCI was proposed to simply be a low magnetic trip breaker.

Research was done and it was theorized that the lowest perspective short circuit current at the panel (consumer unit) plus the highest anticipated circuit impedance would result in a minimum short circuit current of 75amps at the furthest point in the circuit.

However a 75 amp magnetic pickup would result on tripping on inrush with vaccuum cleaners, window ACs and even incandescent light bulbs burning out.

Thus came the idea of an electronic AFCI. One that could discriminate between the current surge of a vacuum cleaner starting and that of a short circuit. Although come reality electricians were and still do get call backs on vaccum cleaners and tools tripping AFCIs.

Even Joseph C Engel, one of the main developers of the electronic AFCIs now has his doubts:



My reply from my other thread:

An AFDD is money secured for the manufacturer. Come time AFDDs will probably have self test logic, meaning they will lock out every X years and require replacement. Already being done with US GFCIs.


AFCIs got into the NEC because manufacturers (like Eaton) bribed the code making panels and UL. They want to and are grdually doing the same with the IEC through committees.


Manufacturers know electrical equipment is near perfected and cheap, I mean what else is capable of lasting 60+ years? But if you require products through mandates, especially products that will require replacement the financial reward is in orders of magnitude greater then before. Investing millions will give you billions, and investing billions will give you trillions. With millions and billions its not hard to cook up a lie one great enough that most everyone will believe.
 
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I don't have time now to get caught up in this debate, but one quick thought;

We have to be a careful comparing US 120V circuits with European 230V. I appreciate that many US buildings have a few 240V circuits too, but numerically the 120V circuit prevails. Some important parameters vary as the square of the voltage or current, so there can be a factor of four differentiating the behaviour of US and UK general purpose circuits. Series arcs also have noticeably different characteristics and form in different situations at 230V vs. 120V. When looking statistically at the causes of actual fires, as well as detail differences in electrical technique, such as the kind of conduit used (or not), one has to allow for differences in building construction, climate and other external factors that affect how a particular electrical event relates to a fire outcome.

Of course. And do you seriously believe the IEC/BS7671 has not addressed the risk of of having a higher voltage to ground long ago?

Have a look at this:






The poster admits that it blew the 16 amp fuse the circuit was run for but not the 32 amp fuse. Further if that circuit had an RCD, the RCD would also have tripped since there is an earthing conductor sandwiched between the live and neutral.


Loop impedance, disconnect times and RCDs are not just about protecting people, but also mitigating fires as well.


The US on the other hand has never had disconnect times or loop impedance requirements...


It is a complex subject and for the fireside observer, personal opinions about 'fraud' and 'rip-offs' are likely to heavily bias the view of what little technical information is available from controlled studies.


The studies in of themselves show the history, one which says the UK system in its current state does the exact same thing as an AFCI.

Remember that this all started with people trying to emulate the British/EU system and thats stated on black and white.
 
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Wow. Its really antiques. Were you found it?

This site:





Reason I keep linking to him is that manufacturers were not only inspired by his theory, but UL also repeatedly sites his findings using it as a bases for picking up where he left off.
 
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To backup my claim about UL's desire for a 75 amp magnetic trip breaker, starting on page 8 with "Lowering the Instantaneous Trip Level of Circuit Breakers":




Page 11

The results of the study sponsored by the EIA determined that lowering the instantaneous trip level below 105 A rms would provide a greater potential reduction in fire risk. Lowering the instantaneous trip level to 75 A rms to cover all receptacles would also increase the possibility of nuisance tripping. AFCI technology, on the other hand, has the ability to detect the current signatures of parallel arcs so that the effective in stantaneous trip level can be lowered to 70 A rms without the increased risk of nuisance tripping.
 
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Pete999

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Derailed another thread with AFDDs, so I am starting this one. I will simply say that UK RCDs and MCBs provide arc fault protection as is. UL not only knows that, but extensively researched UK power systems in an effort to emulate the very same concept 40 years. One the simply fact (growing concern) that the US National Electrical Code does not prohibit a maximum earth fault loop impedance.
 
T

The Ghost

The above states emphatically AFDD and RCD detect different events RCD does NOT detect arcs AFDD do. End of case? Not being an electrical engineer I would not like to hazard any conclusions on this but certainly something to think about.
 
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The above states emphatically AFDD and RCD detect different events RCD does NOT detect arcs AFDD do. End of case? Not being an electrical engineer I would not like to hazard any conclusions on this but certainly something to think about.
RCDs do not trip on a current ripple, but if the arc is going to ground you bet it will trip the RCD.
 

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