A technical question regarding the use of AFDDs

[Pete999]

I seem to remember whilst at the NICEIC film show (oh by the way I believe NAPIT are doing a roadshow as well, lets hope its better than the NICEIC one, see Julys PE for details)
One of the things I remembered from the very limited information given out, was the fact that AFDDS would not be suitable for use on a RFC , explanatios weren't very clear, with no way of asking questions, on to the next topic PDQ.
Does anyone have or know why this is so? would be nice to find out, so if any of you technophobes have any idea, could you post up your thoughts.

 

[telectrix]

maybe because the switches on sockets arc a bit when switching under load.

 

[Richard Burns]

According to the Beama guide to AFDDs:
An AFDD will afford the necessary protection to a ring final circuit including to the equipment connected to the ring. It should be noted that a series arc in a leg of a ring final circuit (for example due to a break in the conductor or a loose connection) will not be of a sufficient magnitude to pose a fire hazard as a result of that arcing. In such an occurrence, the arcing will be minimal presenting a high resistance causing the load current to flow through the other leg of the ring final circuit and as such will not be detected by an AFDD.

 

[Midwest]

Curtesy of Hager;

Contrary to common belief, AFDD’s do offer protection against arc faults in ring final circuits and to the equipment being fed from this circuit. A series arc fault in one leg however, is unlikely to be at a dangerous level so will not be detected. This is due to current in this instance flowing around the other leg of the ring. A series arc fault will be detected in equipment and in flexible cables connected to the ring final circuit. Parallel arc faults are detected and disconnected in all parts of the ring circuit and on all connected equipment.

Underlined the additional bit to Richards answer.

BEAMA do a guide as well.

 

[Pete999]

Thanks to Richard, Tel and Midwest, so I misunderstood the NIC explanation? Or the NIC info was duff? I did wonder at the time "what is the point of using them if you couldn't use them in RFCs. thanks again Lads cleared that little issue up very nicely, no more sleepless nights worrying about it now

 

[Bobster]

Thanks to Richard, Tel and Midwest, so I misunderstood the NIC explanation? Or the NIC info was duff? I did wonder at the time "what is the point of using them if you couldn't use them in RFCs. thanks again Lads cleared that little issue up very nicely, no more sleepless nights worrying about it now

The NIC information probably wasn't the best. There's been a lot of misconception surrounding them.

I've seen and used them in the US, now I'm not sure if the construction of the units are to the same standards in the European models (can't see why not).

They are far more of a nuisance than anything. The idea behind it makes sense, however they are being introduced before the technology is properly functional.

Can you imagine the amount of ----ed off people there are going to be, half the house trips out everytime the compressor in the fridge switches on for example.

Oh, and there is no way of testing one outside of a laboratory. Do you think each one will be tested before reaching the market?

 

[Pete999]

The NIC information probably wasn't the best. There's been a lot of misconception surrounding them.

I've seen and used them in the US, now I'm not sure if the construction of the units are to the same standards in the European models (can't see why not).

They are far more of a nuisance than anything. The idea behind it makes sense, however they are being introduced before the technology is properly functional.

Can you imagine the amount of ****ed off people there are going to be, half the house trips out everytime the compressor in the fridge switches on for example.

Oh, and there is no way of testing one outside of a laboratory. Do you think each one will be tested before reaching the market?

Do Bears s--t in the woods? thanks Rob

 

[ipf]

I can't see any reason for installing any re settable, electro/mechanical operational protective device without a method of test operation. Maybe I need to get a bit more savvy.

 

[Midwest]

They have a test button and apparently they test themselves periodically; and if they are not happy, will turn themselves off. Can you imagine the chaos thats gonna cause

Still we most not act like Luddites.

 

[ipf]

They have a test button and apparently they test themselves periodically; and if they are not happy, will turn themselves off. Can you imagine the chaos thats gonna cause

Still we most not act like Luddites.

I can see the hammer being taken to a few distribution units, too.

 

[Richard Burns]

Courtesy of Hager;
Contrary to common belief

I misunderstood the NIC explanation? Or the NIC info was duff?

The NIC information probably wasn't the best. There's been a lot of misconception surrounding them.

Presumably NICEIC are pandering to common beliefs and misconceptions rather than technically detailed information, who would have thought it!

 

[Midwest]

Presumably NICEIC are pandering to common beliefs and misconceptions rather than technically detailed information, who would have thought it!

Actually, I got my brief, same as the Hager guidance, from Certsure's Connection magazine, just couldn't find it for the OP, so used Hagers.

Perhaps the 'Faraday Lecture' resulted in Chinese whispers or miscomprehension?

 

[netblindpaul]

Midwests post is about the best summary you will get, mind I gather Hager are buying their AFDD in from another of the big players!

The technology is immature yet and not ready for market.
There are similarities in the devices between the EN & the US standard, but I know that one of the biggest players HQ based in Germany, believes that the US spec is rubbish compared to the EU one.
I will find out more next week when I get an "18th ready" board from one of the OEM's I hope...

 

[static zap]

If the clue is it needs all the current , and RFC divides it ...
Hinting at thicker radials ?
( or regular testing - still a must .. fall-back needed )
Don't go thinking this tech can save money in the long run !