Amendment 2 and AFDD's

[IAmSparkytus!]

Is anyone else having problems with the website? This is the only place it's letting me click on/post a message! ?

 

[AJshep]

I can see some cases for them, but the cost/benefit looks very poor to me.

They do work on RFC but don't detect an open ring as practically no arcing takes place there as voltage difference is very small, however, they should detect arc faults on appliance cables that are attached that are above the few amps threshold.

But again, where is the evidence for their use? That is a proper analysis of fire (or near fire fault) cases that clearly would have been stopped by an AFDD and not things like lint fires in tumble dryers, etc.

I agree, I know alot of electrical fires are due to faulty white goods, there has been talk that it is in fact the white goods industry are pushing for us to incorporate AFDD to protect plugged in equipment.
It all seems like a box ticking exercise to me, there's no data I'm aware of.

 

[Resu]

I agree, I know alot of electrical fires are due to faulty white goods, there has been talk that it is in fact the white goods industry are pushing for us to incorporate AFDD to protect plugged in equipment.
It all seems like a box ticking exercise to me, there's no data I'm aware of.

Maybe we should be pushing for the white goods industry to stop throwing cheaper & cheaper components into their appliances then we wouldn't have this problem!

 

[Cookie]

isn't that the sdame for an afci?

~S~

AFCIs used to have 30/50ma ground fault protection in them, but some of the US manufacturers took it out in favor of looking at the current signature alone.

 

[Cookie]

I can see some cases for them, but the cost/benefit looks very poor to me.

They do work on RFC but don't detect an open ring as practically no arcing takes place there as voltage difference is very small, however, they should detect arc faults on appliance cables that are attached that are above the few amps threshold.

But again, where is the evidence for their use? That is a proper analysis of fire (or near fire fault) cases that clearly would have been stopped by an AFDD and not things like lint fires in tumble dryers, etc.

Funny you mention evidence. In the US, other than cut wire wrapped in glass tape and hooked up to a neon gas transformer in a laboratory there is zero evidence that arcing is behind any residential fires to begin with.

There is the case of firefighters opening walls to find smoldering studs with romex stapled across them. However, pyrophoric carbonization from an energized staple likely to be the real cause behind these events was and is miss-theorized into arcing. Ignoring the evidence of dried wood around nails and the foundation some distance from the smoldering area indicative of low level current leakage over the years and not arcing.

 

[Dustydazzler]

How about individual 13a sockets with Built in Arc Fault Interruption then ???

 

[Cookie]

How about individual 13a sockets with Built in Arc Fault Interruption then ???

Thats what the plug top fuse is for, literally. A short in the flex will open the fuse within 3 cycles. Though anyone here can correct me on that if not so in practice.

 

[DPG]

Thats what the plug top fuse is for, literally. A short in the flex will open the fuse within 3 cycles. Though anyone here can correct me on that if not so in practice.

A 13A fuse won't blow on an arc fault though. A fuse takes a relatively long time to open.

 

[AJshep]

Maybe we should be pushing for the white goods industry to stop throwing cheaper & cheaper components into their appliances then we wouldn't have this problem!

And that is the problem, accordingly to what I've heard, committee that wrote the standards are made up manufacturers, in white goods industry.

 

[AJshep]

This is a interesting take on AFDD from Paul M and JW from the E5 group. It pretty much highlights all the issues we've been talking about.

skip to around the 40min mark to hear their views

 

[Cookie]

A 13A fuse won't blow on an arc fault though. A fuse takes a relatively long time to open.

Do have a time current curve to common BS1363 fuses?

The flex itself typically adds only a small amount if impedance to the fault loop.

 

[LastManOnline]

Another difference between the UK and the USA.. UK installs AFDD in the distribution board, where as the USA favours them at outlet sockets.

Installing the AFDD at the socket outlet is surely an acknowledgement that white goods are the main issue

 

[SJD]

Thats what the plug top fuse is for, literally. A short in the flex will open the fuse within 3 cycles. Though anyone here can correct me on that if not so in practice.

I understood that an AFDD should be detecting an intermittent rapid change in current e.g. a loose connection in L or in N that is arcing (and which would likely not blow any fuse).

 

[pc1966]

And that is the problem, accordingly to what I've heard, committee that wrote the standards are made up manufacturers, in white goods industry.

Then why not have them fitted to the appliance plug? They can bear the cost if they think it is important...

 

[pc1966]

Do have a time current curve to common BS1363 fuses?

Here is the typical plot, not as well defined as BS88 fuses:

 

[Cookie]

I understood that an AFDD should be detecting an intermittent rapid change in current e.g. a loose connection in L or in N that is arcing (and which would likely not blow any fuse).

A parallel L-N or L-E event will blow the fuse.

A series event without an outer screen to earth itself out to would technically require an AFDD, however, I do not believe partially severed cords are behind any number of fires. I aslo do not believe that AFDDs accurately detect dangerous arcing. Cost effective AFDDs will always be a compromise between tripping on dangerous arcing and not tripping on electronics, vacuums, drills and the like. All to often one is indistinguishable from the other and the 1.5-5 amp series current pickup is part of that compromise.

 

[DPG]

A parallel L-N or L-E event will blow the fuse.

A series event without an outer screen to earth itself out to would technically require an AFDD, however, I do not believe partially severed cords are behind any number of fires. I aslo do not believe that AFDDs accurately detect dangerous arcing. Cost effective AFDDs will always be a compromise between tripping on dangerous arcing and not tripping on electronics, vacuums, drills and the like. All to often one is indistinguishable from the other and the 1.5-5 amp series current pickup is part of that compromise.

A brief L-N arc event will not rupture a 13A fuse.

 

[Cookie]

A brief L-N arc event will not rupture a 13A fuse.

From what I understand (and could be wrong) a 32 amp MCB has a max Ze of 1.15 ohms or 200 amps of perspective fault current at the furthest point of the socket. 200/13 would be 15 times the rating. Thus 200 amps trips a TDC180 British plug to fuse in under 0.01 seconds.

https://www.eaton.com/content/dam/e...s/data-sheet/eaton-tdc180-fuse-data-sheet.pdf

This is assuming TDC180 fuses are of the same kind used in the UK.

 

[pc1966]

This is assuming TDC180 fuses are of the same kind used in the UK.

From above curve, worst-case it is 0.03s at 200A PFC.

I guess the real question is what sort of fault will start a fire but only an AFDD will trip, and how common/likely are they?

In my limited experience of sorting out fixed wiring, the only two cases of a long-term serial arc were light bulb holders in the days of 60W/100W lights and you could sometimes here the buzzing and see the light dim slightly. Yes, those are circuits for which AFDD are not recommended...

 

[Aaron b]

Does anyone know the figures for the improvement from fitting these devices in Germany? I can't see how any figures could be of value as if a competent person installs an AFDD board they are also going to check the condition of the installation and could remove fire hazards skewing the results.