Are AFDD's worth it for domestic properties getting rewired?

[eveares]

As I understand it, at the time of writing this (01/04/2025), AFDD's are not mandatory under the current BS7671 18th edition Amendment 3 in most typical domestic settings, however is it worth fitting them if a old place was getting re-wired, say a 3 bed semi detached house? (Yes I know it's the pervious Amendment 2 what covers AFDD's.)

From what I know, they are now mandatory on final circuits feeding socket outlets not exceeding 32A in high rise buildings, HMO's, student accommodation and care homes.

It's just that compared to regular type A B-Curve RCBO's, AFDD's are so damn expensive! Also is there any place you would not use them? Say on a 6A lighting circuit, a 40A circuit feeding a hot tub, 20A electric oven circuit, a 16A circuit feeding a UPS then feeding a Data rack, etc...

What would you do if you needed to rewire and install a new DB in your typical suburban 3 bed semi-detached house that was not a high risk place like a HMO or student accommodation? (See poll)

Regards: Elliott.

 

[blup]

I think they are the way to go along with SPD’s. It’s progress, otherwise lighting circuits would still not be earthed, on the grounds it’s not really necessary

 

[Murdochcat]

No don’t bother fitting them. If the regs change later it’ll be a simple job to take out a RCBO and replace with an AFDD

 

[ebee]

NO

 

[Murdochcat]

I think they are the way to go along with SPD’s. It’s progress, otherwise lighting circuits would still not be earthed, on the grounds it’s not really necessary

These changes are to ensure new editions are required, nothing more, nothing less

 

[eveares]

These changes are to ensure new editions are required, nothing more, nothing less

You saying there is no need for things to improve over the decades? You can hardly argue against that adding a CPC to lighting circuits (14th edition) or protecting nearly all sockets with a 30ma RCD (16th edition) for example was a good thing surely?

 

[ebee]

I`m happy to agree that earthing, bonding, RCDs and maybe SPDs are a good idea but not AFDDs.

Car seatbelts, Airbags, Crumple zones etc etc are a good idea in cars too.

The one problem with all of these good ideas is that some people tend to take more risks therefore the nett result can sometimes be more danger.
Lots of folks nowadays are indestructible (in their own minds)

 

[ericmark]

There was an old thread re-started about RCD's, with the same questions asked. But I know in the early days of RCD's they had so many nuisance trips, today with modern RCBO's and equipment designed for use with RCD's we don't seem to have the problem. But back to AFDD, the important thing is testing, is an AFDD at fault, or is some wiring or appliance at fault, so I did a Google hunt for testers.

I was surprised at the lack of testers, found a YouTube video

and he finally gets to AFDD near the end, 9.25 into the video, and then nothing on how to test the AFDD just that it tripped with the pop-up sockets, but not direct. That is unsatisfactory to my mind. I want to be able to connect a tester, and it says the AFDD is too sensitive, or no sensitive enough, until there is a way to test them, they are a non-starter.

He shows in the video testing leakage

this is something we all do today (I hope) so we know how close to the wind we are sailing, without the clamp-on, I relied on the RCD tester, if it did not trip at ½ rating, then likely the leakage was low enough, since typical is 26 mA then we would assume less than 11 mA if no trip at ½ rating, OK, pass mark is 30% or 9 mA with a 30 mA trip, but we have always tested RCD's to see if within spec, to fit a AFDD without testing just seems crazy.

 

[EFLImpudence]

You saying there is no need for things to improve over the decades?

Wait until the next thing (whatever that might be) is required and then do both.

You can hardly argue against that adding a CPC to lighting circuits (14th edition)

You can if none of your accessories requires earthing.

or protecting nearly all sockets with a 30ma RCD (16th edition) for example was a good thing surely?

I know what you mean but they are not to protect sockets but people and how many have been saved compared to the huge cost?

 

[ericmark]

I fitted RCD's back in the 90s when my son, then only 14 passed his RAE. So have lived with RCD's at home for some 35 years. The one time I found a cable routed where it should not have been, it still knocked me out, hit the cable with a hack saw blade held in my hand, making a channel down the wall for a water supply to the fridge. Likely the time connected would not have been any longer if no RCD.

As to the minus side, today my freezer does show temperature reached when power is cut, but back in the 90s we did not have that, so found RCD tripped, reset it, and did not know if food in freezer safe to eat or not. Often no idea how long it had been off. And we do not log food poisoning as a result of freezers not working, so we have no idea of the harm done because the RCD was fitted.

I had the RCD trip just before moving house, and remember having to dump the food. No idea how long supply had been off. So in this house we have back-up batteries, so power cut will not cause freezer to stop working, and freezers on their own RCD sockets, what is the point if an AFDD can trip. The route to the consumer unit is outside, down a set of steps, and into the flat under the house where the consumer unit is. There is clearly a danger doing this in the dark, and specially if there is ice or snow, I would hope if a RCBO trips, I can leave it until daylight.

It is all well and good doing a risk assessment in a house with emergency lights, and a consumer unit in an easy accessible position, but often consumer units are not easy to access, last house it was in the garage, and mother house under the stairs, completely inaccessible for my mother in a wheelchair.

The picture of the fire, are you really saying the RCD did not trip? The news services love their pictures, ⁣ but as to reporting if RCD fitted, or smoke alarm fitted, never mind AFDD, nothing. As to a report, Mr. X taken to hospital due to a fall in the ice while outside going to garage to reset RCD, it will only say he had a fall, nothing about why he was outside.

I have now put in handrails most of the way down to flat, where the consumer unit is. But there is still a risk involved resetting RCBO's at night. To fit AFDD to my mind not worth the risk.

 

[JohnW2]

You saying there is no need for things to improve over the decades?

That would be foolish. So, in my opinion, would it be foolish to implement things just because they became technologically possible unless they were clearly addressing a significant problem - and I am personally as yet far from convinced that fauklts resulting in arcs are, in domestic settings, responsible for a significant number of fires.

You can hardly argue against that adding a CPC to lighting circuits (14th edition) or protecting nearly all sockets with a 30ma RCD (16th edition) for example was a good thing surely?

One definitely could 'debate' those things.

Addition of CPCs to lighting circuits was a pretty trivial thing to implement (for new installations or re-wires), so probably sensible, although I'm not sure that an appreciable number of injuries or deaths had been resulting from its absence. RCDs have undoubtedly resulted in some benefit (particularly in clearing faults before anyone had a chance to get a shock) but, as I say so often, I'm pretty sure that a lot more injuries and deaths would have been prevented if the vast amount spent on RCDs had been directed elsewhere (e.g. to road safety or medical care/research).

 

[ebee]

If as some of us had mentioned before, it was not uncommon for folk use a Y splitter on a lampholder to give 1/ the existing lamp and 2/ a metal unearthed iron to do the ironing back in the days when folk had not got enough working sockets scattered about and we would use the same set up to power a tape recorder or something, there were not piles of bodies littering every street corner either.
Lots of homes had one socket upstairs and one socket downstairs and ohh what a good idea that a cooker control switch gave you a handy place to lug the kettle in (or the washing machine or tumble drier).
All circuits were run on rewireable fuses and not a RCD in sight.
Those were the days.
Like another planet compared to today.
A couple of 3KW fan heaters could draw most of single ring final circuit too but we could plug other stuff in and not always get that interesting BANG from the fusebox.
a 30A bang from those old fuses was certainly more interesting than 15A or 5A bangs!

 

[Murdochcat]

You saying there is no need for things to improve over the decades? You can hardly argue against that adding a CPC to lighting circuits (14th edition) or protecting nearly all sockets with a 30ma RCD (16th edition) for example was a good thing surely?

Amendments every 2-3 years is utter nonsense

5 years would make sense

And people still think RCD protection isn’t required

 

[ebee]

Well if the intervals make it more frequent than 2 to 3 years it could be a bit of a mindfield to follow the changes both in intent and in practice perhaps,
Every 5 years in some cases could be too long a period.
So to set a figure in stone would not always be helpful anyway.
It depends upon the changes themselves and the actual impact or the potential impact of such.
An agreement by the great and good with regard to the cir umstances at that time is probably the best (or the least worst) solution .

 

[Murdochcat]

Well if the intervals make it more frequent than 2 to 3 years it could be a bit of a mindfield to follow the changes both in intent and in practice perhaps,
Every 5 years in some cases could be too long a period.
So to set a figure in stone would not always be helpful anyway.
It depends upon the changes themselves and the actual impact or the potential impact of such.
An agreement by the great and good with regard to the cir umstances at that time is probably the best (or the least worst) solution .

You clearly have no idea of the minor changes they implement to justify the new editions