A.F.D.D. with a combined M.C.B. unit, the tripping may just be due to overcurrent, so we may not know which part of the device has caused the tripping off.

All the ones I looked at had some means of indicating the cause of the trip - usually coloured/flashing LED - different flashes for Arcs, RCD or overcurrent - so probably better than many an RCBO.

  - Andy.

RCDs, SPDs, Fuses, MCBs etc are merely passive components. We know how they are supposed to work and can test them up to a point. They are 'dumb' and just sit there until the condition they are designed to address occurs.

AFDDs are active devices which contain a cpu and are driven by algorithms. One might say they are semi-'smart'.

AFDDs are a completely different ballgame to the other passive devices I have mentioned.

We have all witnessed how good algorithms are when it comes to writing and applying them into real world problems.

I recall a certain now-infamous Professor predicting something like half a million deaths in the UK at the beginning of the pandemic..................

Then of course, we have algorithm-driven 'bots' which drive search engines and the like. Type certain words into a search engine and you might not get what you were looking, but something embarrassingly different!

It wouldn't take a great leap into the unknown to predict 'smart' consumer units, which would be capable of monitoring a preloaded load profile for every appliance in your house. Couple this via some metadata to your smart meter and your supplier could look up what you have switched on at any time.

"Flashing red light on Supplier's control room console summons the attention of the keyboard operative  - Mrs Gumby has her washer and dryer on and the windmill isn't turning - switch her off NOW!"

Down the wire goes the 'Make It Dead' signal to the relevant 'smart' circuit breaker in Mrs Gumby's cu  and off goes her washing until the wind blows again.

Just because we might be able to do something doesn't always mean that we should.

whjohnson said:

I recall a certain now-infamous Professor predicting something like half a million deaths in the UK at the beginning of the pandemic

That was the predicted death toll for if the government took no action. So the government took lots of actions - lockdowns etc - and the actual death toll was reduced to about a third of that.

H.M.O.s are often privately owned. The question is WHEN do these unproven "fire preventing" devices have to be installed? In existing installations?

Z.

Then when Mrs. Gumby's clothes get smelly and mouldy in the machine she has to put them on at least one or maybe two new wash cycles to remove the smells.

Z.

And she can't dry them outside because it's raining and the wind isn't blowing!

Never mind eh, Mrs Gumby is delighted to be doing her bit for the environment despite being charged a hefty premium to put up with regular supply interruptions.

I wonder which of his algorithms told him it was ok to visit his German mistress despite his own advice to the rest of us?

whjohnson said:

AFDDs are a completely different ballgame to the other passive devices I have mentioned.

Circuit-breakers have, for some time, had intelligence in them. Granted, not the "for use by ordinary persons" breakers, but it's nothing new to me to see "computers" in protective devices.

I think you're dead right, that there's way more mileage out of "SMART" devices to be marketed in the future.

Wife phoning husband who is at work.

"George there's an  arc fault on our wiring I'm worried about a possible fire"

George; "Are you sure dear?"

Wife. "Yes George there are flashing lights."

George. "Can you see or smell smoke?"

Wife. "No George, but the lights are still flashing."

George. "I have an important meeting in 30 minutes here."

Wife. "Can't you come home George, I'm very worried."

George rushes home.

George upon inspecting consumer unit.

"Oh, dear, there's nothing wrong. It's just the flashing lights on the smart meter dear."

Wife. "Well they were signalling a fault dear. They were. Honestly."

Z.

Dear, dear will you spend some time viewing this please........?

Do I really have to?

AFDD - Arc Fault Detection Device - Part 1 - Bing video

"But Dear, when the device switches off after eventually detecting an arc fault it needs to be turned on, possibly to a faulty circuit, before it reveals its reason for switching off. I though that we should not energise a faulty circuit or faulty appliance. That could be dangerous."

Z.

Zoomup said:

"But Dear, when the device switches off after eventually detecting an arc fault it needs to be turned on, possibly to a faulty circuit, before it reveals its reason for switching off. I though that we should not energise a faulty circuit or faulty appliance. That could be dangerous."

Oh dear.

What the FIRST thing that happens when a domestic RCD trips (or, as I've seen, RCD trip at work, that's intended for operation by ordinary persons)?

A user tries to reset it. Simples. Same with mcb's ... only after it trips again will anyone investigate further.

I don't really see that as a clear argument that AFDDs are dangerous. Sorry Zoomup 

Zoomup said:

"But Dear, when the device switches off after eventually detecting an arc fault it needs to be turned on, possibly to a faulty circuit, before it reveals its reason for switching off. I though that we should not energise a faulty circuit or faulty appliance. That could be dangerous."

Oh dear.

What the FIRST thing that happens when a domestic RCD trips (or, as I've seen, RCD trip at work, that's intended for operation by ordinary persons)?

A user tries to reset it. Simples. Same with mcb's ... only after it trips again will anyone investigate further.

I don't really see that as a clear argument that AFDDs are dangerous. Sorry Zoomup 

gkenyon said:

A user tries to reset it. Simples. Same with mcb's ... only after it trips again will anyone investigate further.

Father always said not to replace a fuse until the cause of the blow had been found, but I think that one might be permitted one try with an MCB.

At work, not too long ago, we were informed that we could not have tea because there was no power to the water heater. This was a serious matter. I found a CU, opened the door, saw a tripped MCB and reset it. Doubtless I broke many rules (including standing on a chair rather than a ladder) but I fixed the problem.

A similar near existential crisis at our place had a temporary 3 phase extension lead running between two buildings and up a stairwell to the offending coffee room in  under an hour. That is because it was the one used by site services. The cynic in me suspects that anyone else  would have had to put a ticket in and wait..

Mike

Recently a fast food takeaway had a problem with a walk in chiller room cooling system. It kept tripping everything off including chest freezers full of food on the same circuit. The compressor motor had gone short circuit L to E. The owner had tried to run the walk in chiller room via a long extension lead on a good working socket outlet. As the compressor was still faulty it caused an immediate tripping off of a M.C.B. It also damaged the socket outlet switch so that it became faulty. It is not a good idea to liven up a faulty circuit. The first trip tells you that something is faulty. Don't tempt Darwinism.

Z.

So, an A.F.D.D. trips off due to a fault, then is reset by somebody but it won't stay on. Do the flashing lights stay on that identify the type of fault?

AND, what benefit is there in knowing the type of fault anyway by the flashing lights, as an electrician will normally and hopefully locate it by conventional means anyway. 

Z.

Zoomup said:

So, an A.F.D.D. trips off due to a fault, then is reset by somebody but it won't stay on. Do the flashing lights stay on that identify the type of fault?

AND, what benefit is there in knowing the type of fault anyway by the flashing lights, as an electrician will normally and hopefully locate it by conventional means anyway. 

Different manufacturers have different implementations, and you'd need to check specific products out, but why wouldn't the electronics inside the AFDD be able to stay on from the input, whilst the output circuit (containing the supposed fault) is disconnected?

I was wondering about the longevity of these things. How many non-arc faults - over-current/short circuit -  will they tolerate before the electronics gives up the ghost? There's a arc extinguishing chute in there somewhere which needs to snuff out heavy fault current arcs withing the device itself.  I know that certain brands of RCBO tend to die after relatively few operations under service conditions. That'll be one hell of an expensive 'fuse' to replace when it fails.

All protective devices are only specified to operate for a finite number of times (in the case of fuses themselves, 1).

Indeed. But there is a lot of variance in terms of resilience between products from different manufacturers when it comes to electro-mechanical devices, and now we intend to introduce fragile silicon chips into the mix.

whjohnson said:

and now we intend to introduce fragile silicon chips into the mix

They are here already in other protective devices - for HV and very large LV installations ... and have been for over 25 years.

If your installation has multiple arc faults, then you have bigger things to worry about than how long your AFDD is going to last.