AFDDs for single-socket circuits

Selfmade · Aug 13, 2022

Haven't been on here for a while, so sorry if this has been discussed before.

BS7671 2018 + A2 Regulation 421.1.7 recommends AFDDs for "single-phase AC circuits supplying socket outlets..." (requires in certain premises). My intention is that from September 27th I will recommend them to customers (in practice I already do in some situations) and require a signed waiver if they don't want the expense. At least I will do so for the actual Sockets Circuits - typically ring final, serving a number of sockets for general use and sometimes also fixed equipment via FCUs.

What I'm not sure about is circuits that serve just a single socket, such as a dedicated circuit for a fridge or an oven. In the case of a fridge, it will likely draw less than 2A, so an AFDD is unlikely to perform any useful function. In the case of an oven, one could justify cutting off the plug and connecting it via an FCU, in which case the circuit is no longer supplying a socket, yet with or without a socket it's still the same appliance and the same wiring. Yet in both cases if a socket is fitted an AFDD is recommended according to the regs.

BTW I understand a case could be made for AFDD protection for an oven and oven circuit. But for this question I'm just interested in the definition of 'circuits supplying socket outlets' for the purposes of this recommendation.

Dustydazzler · Aug 14, 2022

GBDamo said:
Quite, AFDFs are a solution in desperate need of a problem.

Agree

They are invention ahead of their time as the problem hasn;t been invented yet

davesparks · Aug 14, 2022

Dustydazzler said:
The fact we can't test them is neither here nor there Imo , as you say we fit millions of MCBs each month and have no idea if they work proper or not.
My issue with AFFDDDs is I honestly don't feel that they are necessary in the UK

Yes we do, but MCB's are batch tested and generally proven to be a pretty reliable technology. Plus they are a fairly basic mechanical device which doesn't rely on electronics.
Plus if an MCB is tripping it is almost always possible to find the cause with regular test equipment that we all have. We can pretty easily test whether an MCB is over-sensitive.

Afdds are presumably also batch tested, but they rely on sophisticated electronics to work which increases the opportunity for failures, especially when engineered down to a price.
We have no way of realistically testing for what may have caused an afdd to trip at the moment, and no way to work out if it is being over-sensitive.

Dustydazzler · Aug 14, 2022

I remember a few years ago watching a YouTube video of an electrician trying to get to the bottom of a tripping AFCI on a socket circuit on a new house. He couldn't get the AFCI to hold in SO guess what he did...

Removed the AFCi and put the circuit on a standard MCB

If that is the American solution to a tripping AFCi then why bother in the first place ?

Selfmade · Aug 14, 2022

DPG said:
Although I get it that some people are reluctant to fit AFDDs partly because no testing can be done, bear in mind we don't test MCBs either.

True, although at least in the event of an MCB trip we can break up and test sections of the circuit to find the location of the fault.

UNG · Aug 15, 2022

DPG said:
Although I get it that some people are reluctant to fit AFDDs partly because no testing can be done, bear in mind we don't test MCBs either.

If we wanted to spend a lot of money there is test equipment available for MCB's, I have done many searches for AFDD test equipment and found none

Dustydazzler said:
The fact we can't test them is neither here nor there Imo , as you say we fit millions of MCBs each month and have no idea if they work proper or not.
My issue with AFFDDDs is I honestly don't feel that they are necessary in the UK

MCB's are so cheap that no one really bothers if a suspect one is replaced, a suspect AFDD replacement is a considered cost and the decision can't be taken lightly

Dustydazzler said:
From what I have seen on YouTube from America the more expensive AFCI / AFFDDDs are Self Testing

How do you have faith and trust in a self test, the AFDD says it is working correctly so it must be right and the circuit is faulty and so the pantomime starts. It says it all with AFDD's when Hager has produced an AFDD that can be reprogrammed to ignore circuit noise that the AFDD may inadvertantly react to

davesparks said:
Afdds are presumably also batch tested, but they rely on sophisticated electronics to work which increases the opportunity for failures, especially when engineered down to a price.

And firmware / software that could become corrupt from mains noise or voltage spikes is that why the SPD came before the AFDD

davesparks said:
We have no way of realistically testing for what may have caused an afdd to trip at the moment, and no way to work out if it is being over-sensitive.

As previously mentioned Hager do have monitoring tools and their AFDD can be reproogrammed but I can't help but feel it's a kings new clothes situation you programme out the senstivity and all you end up with is a fancy bit of kit in the box to meet the requirements of the regs but it performs no other function

In recent years we have had requirements to fit SPD's and now AFDD's but nowhere have I seen any documentation, facts or real world reasons / case studies to support there introduction or to enable us to better inform our clients and customers as to the benefits of having them installed in their installation

Markyd · Aug 15, 2022

davesparks said:
Which regulation states that a waiver is required?

3 mins into vid

Dustydazzler · Aug 15, 2022

Rather than messing about with Waivers

I will probably end up doing 2 quotes for future board changes

Quote 1 - The expensive option with AFFDDDs

Quote 2 - The slightly less expensive option without AFFDDDs

On the bottom of quote 2 , it is say that AFFDDDs were offered as an upgraded option but declined

timhoward · Aug 15, 2022

Markyd said:
3 mins into vid

None of that text is in the regs.
They have made it look like it is, but it isn't.

All the regs say is:
"For other premises, the use of AFDDs conforming to BS EN 62606 is recommended for single-phases AC final circuits supplying socket-outlets not exceeding 32A"

Markyd · Aug 15, 2022

timhoward said:
None of that text is in the regs.
They have made it look like it is, but it isn't.

All the regs say is:
"For other premises, the use of AFDDs conforming to BS EN 62606 is recommended for single-phases AC final circuits supplying socket-outlets not exceeding 32A"

If you dont want to cover your backside....... You carry on then.......

Dustydazzler · Aug 15, 2022

I guess the other thing to possibly consider , if if you fit a fully RCBOs board as the customer can't afford the upgrade to AFFDDDs , should we make sure that we are fitting boards that at a latter date the home owner could swap out some of the RCBOs for AFFDDDs. Will all makes of consumer unit offer a AFFDDD that will fit in a single way in their current board models

loz2754 · Aug 15, 2022

As AFDDs are recommended in all other situations than those specified in the regs, some installers would choose to pass on the recommendation (along with the cost).

But there are many uses of the word "recommended" in the regs. Should we follow the same logic of covering our own arrses and pass on these recommendations as well?

timhoward · Aug 15, 2022

Markyd said:
If you dont want to cover your backside....... You carry on then.......

I don't actually feel any need to when page 18 of the regs clearly defines normative and informative elements.
As @loz2754 points out it would be a long list to get waivers signed for everything that is recommended that we don't do.

I prefer to tell customers what is required and what is recommended and help them make informed choices. Making them sign something is (to my mind) creating a false impression of severity relating to the consequences.

Welchyboy1 · Aug 15, 2022

Markyd said:
Yes AFDDs are only a recommendation but after September will need a waiver signed by the client to say they dont want them, which will cover you when their tv blows up and they say you didnt recommend using one

Isn’t that SPDs?

Markyd · Aug 15, 2022

Welchyboy1 said:
Isn’t that SPDs?

After Sept SPDs are mandatory and the only way you can get out of fitting one is if the customer signs a waiver.

Dustydazzler · Aug 15, 2022

Markyd said:
NO....after Sept SPDs are mandetory

Will they come supplied 'as Standard' with every Screwfix special consumer unit ?

Bet they don't

davesparks · Aug 15, 2022

Markyd said:
3 mins into vid

That's not the regulations, that's the video creators opinion of what the regulations should say.

ipf · Aug 15, 2022

Selfmade said:
Arc Fault Finding Damage Detection Devices?

AFFDDD....I can understand (or imagine, at least) what the extra F stands for, you could even put it in front of the A.....it's all those D's that confuse me.

mainline · Aug 15, 2022

Dustydazzler said:
Will my TV blow up if I don't fit an AFFDDD ?

Yes it will in the end buts that's whether you fit one or not

mainline · Aug 15, 2022

Selfmade said:
Ahhhh yes but the customer might want them and might be happy to pay for them. Who am I to make a value judgement on their cost/benefit analysis?

Personally if I was doing a CU in my own home I'd probably fit an AFDD for the kitchen sockets but not bother elsewhere.

You should also point out to the customer that the device will fail at some point, but you don't know when

Welchyboy1 · Aug 16, 2022

Ha that’s a good one! Must be a manufacturers video

what works are not primarily designed and engineered around cost

so how much is a CU change going to be now approx?

8-10 type A rcbos, SPD, 12way board with main switch, approx 3 afdds for socket circuits, plus bits and pieces, days labour for fitting and testing, plus allowance for returning to site for further investigation if afdd starts playing up on an appliance that you couldn't detect during testing

must be talking £1000-1200 plus a bit of VAT

thats going to be a hard sell for most electricians I would guess depending on your area in the country

like others have said, I think I will be offering budget, mid-range and premium versions of a consumer unit change

pc1966 · Aug 16, 2022

Just now a quick search for the Fusebox brand has RCBO for around £15+VAT and AFDD for around £105+VAT, so around £110 extra parts cost per circuit to the customer (inc VAT), and a bit of margin for returns and call outs for odd trips, so say £150.

Not sure what is typical for a home these days, but it is looking like £300-450 extra if you have 2-3 RFC and if not much else (couple of lights, couple of fixed kitchen appliances), then it is probably adding 50% to a CU change?

Some folk won't have issues with the cost but I bet the majority of customers do! More so when it is a hard sell as to what they really offer in terms of improved safety. We see general fire stats quoted from time to time but so far I have not seen an analysis of what AFDD would have likely stopped versus stuff they would not have detected.

Sure if the were down to £20 versus £15 for RCBO then nobody is going to have a big issue with them, but just now it is going to be a problem for many.

timhoward · Aug 16, 2022

pc1966 said:
More so when it is a hard sell as to what they really offer in terms of improved safety

There's a certain amount of chicken and egg here, until they end up in more installations we won't see if electrical fire statistics fall in general terms.
What could completely throw the stats is lockdown and the amount of time people spent working at home, and then people returning to workplaces, leading to a rise and fall in domestic fires.

I've had a quick look at some publicly available data:

Percentage of fires, non-fatal casualties and fire-related fatalities in accidental dwelling fires by selected sources of ignition, England; year ending March 2020

[ElectriciansForums.net] AFDDs for single-socket circuits

So electrical-appliance ignition source caused 13% of fires and accounted for 4% of fatalities.
Electrical distribution ignition sources are in fact killing more people.
(Space-heating source fatalities are really quite scary - people plugging in a fan heater in one room and not running the CH is going to be a real issue)

But maybe more relevant is this graph (same year)
Percentage of fires in accidental dwelling, fires by cause of fire, England; year ending March 2020

My conclusion for now - If 15% of fires are being caused by faulty appliances then maybe our advice should simply be that AFDDs are an attempt to bring down that number. The reality is that we won't know if it works for several years.

What could help would be some government funded TV adverts, like the original "Wake up - get a smoke alarm" campaign.

Markyd · Aug 16, 2022

Looking at about £150 for a RCBO/AFDD all in one unit

Dustydazzler · Aug 16, 2022

Markyd said:
Looking at about £150 for a RCBO/AFDD all in one unit

Standard domestic new build looking at around 10-15 circuits

£1500 on devices isn't too bad when you think what the overall build cost is these days

timhoward · Aug 16, 2022

Dustydazzler said:
Standard domestic new build looking at around 10-15 circuits

£1500 on devices isn't too bad when you think what the overall build cost is these days

Would you fit them to all though, not just sockets?

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