AFDD Q and A

Humm, I'm not sure I follow the logic behind the NICEIC's answer - while I agree that current regs aren't retrospective to the existing installation, they surely do apply to the new work - i.e. the new length of cable and the new socket. I can't see how the addition can be said to comply with the latest regs in such cases if an AFDD wasn't provided. It smacks rather like saying you don't need to correct inadequate or defective main bonding when making an indoors addition that relies on ADS ... because the bonding was part of the existing installation.

   - Andy.

Yes and no!

Earthing and bonding must be adequate for the addition or alteration: 132:16.

More pragmatically, suppose that a customer obtains two quotes. One says that you must have AFDD, the other does not. Which will you choose?

Wouldn’t it make sense to offer two pricing options—one with AFDDs and one without? That way, the client can decide based on their budget and priorities. While AFDDs aren’t a strict requirement, I always explain that they’re recommended (C3 on a EICR) for improving safety. Give the client the information they need to make an informed decision.

You could also go one step further and give options for PVC/PVC T&E vs LS0H.  Caveat time,  there are differences between LSF (Low Smoke and Fume) and LSOH (Low Smoke Zero Halogen) cables.  Now LS0H is not a requirement for a domestic dwelling BUT it is safer if used.  Is this not the realm of a designer and for a small operation the Electrician is the Designer/Installer/Commissioner /Tester

AMK said:

Give the client the information they need to make an informed decision.

And the informed decision will be to go with the cheapest option.

Simon Barker said:

And the informed decision will be to go with the cheapest option.

That's a bit cynical.

I think that I would seek justification for the additional expense - same as for any other tradesman, including a surgeon.

Well a truly informed decision will require the fires and accident figures so lacking from the AFDD sales literature.

Mike.

40 years ago, if you were ill, you tended simply to accept doctor's advice. Nowadays, the decision has to be fully informed or else any odd side effect such as gambling all your savings away, or going a bit kinky as in this week's news is the doctor's fault.

I see no reason why the same principles should not apply to any expert's advice.

This year, my house insurers required me to install better fire detectors. AFDDs were not required, so that must give an indication as to their value.

Wouldn’t it make sense to offer two pricing options—one with AFDDs and one without? That way, the client can decide based on their budget and priorities. While AFDDs aren’t a strict requirement...

In the OP's situation of HRRBs, HMOs, etc, the wording of 421.1.7 is "shall" - which seems like an absolute requirement to me.

Earthing and bonding must be adequate for the addition or alteration: 132:16.

Indeed, but I'd suggest that's not an exception to the rule, but rather it's merely reinforcing the general requirements of 132.16 "No addition or alteration ... shall be made to and existing installation unless it has been ascertained that the rating and condition of any existing equipment ... will be adequate for the altered circumstances".  To my mind that's saying that if we need the supply circuit to have upstream AFDD protection and it's not there, we can't make the addition. Which leaves us with the alternatives of either creating a new circuit with AFDD protection to supply our new socket, or upgrade the exiting circuit so it does.

After all we wouldn't accept high Zs or excessive v.d. on a new socket, just on the ground that it's caused by the existing installation.

(I can appreciate that some of the doubt around the effectiveness of AFDDs may give rise to a temptation to look for ways of omitting them, but that can't really justify undermining the principles of the regs.)

   - Andy.

Hi Andy. I agree that the new circuit should include AFDDs in the specified installations. However, the work being carried out would fall under Regulation 644.1 as a minor works. Does this imply that omitting AFDDs would fail to comply with Regulation 644.1.2

-Andrew

This Technical Bulitin by BEAMA might be worth a red.

www.beama.org.uk/.../technical-bulletin---afdds-performance-with-xlpe-cable.html

This Technical Bulitin by BEAMA might be worth a red.

www.beama.org.uk/.../technical-bulletin---afdds-performance-with-xlpe-cable.html

Thanks for that - this is the sort of research that should have been published about ten years ago, but better late than never (!) It is not coming to the same conclusions as other authors, but the test conditins appear to be far more 'real world' than some of the lab data.
I'll have to digest.
M.

Interesting article. I noted "The test was carried out by energising the circuit, and manipulating the cable conductor break by a few millimetres, to repeatedly make and break electrical connection and cause electrical arcing." - which made me wonder now long a damaged FIXED cable was likely to continue arcing? or whether, if arcing started at all, it would either erode to an non-arcing gap or weld closed again, in fairly short time. If indeed we're expecting the fixed wiring rather than downstream appliances and/or their flexes to be protected.

   - Andy.

yes - repeated movement to get it to reconnect is more the sort of thing thing that happens with extension leads. But it is still a lot more realistic  that pre-burning  the insulation with a high voltage that is in the spec. Another realistic sizzle fault not covered is when things are damp or wet, either with pure water or things like mouse urine, the latter of which I appreciate makes for an awkward test.
It also suggests that the firing within half a second only occurs after the optimum arc has been struck. But this is a different discussion,  one about how useful AFDDs really are with real faults scenarios in practice, not this one, which is more about what the regs think their purpose is.
Mike.

Maybe as a side bar but I think a lot of people are unaware that there are several BS for UK cables.  The type of cable and the type of insulation can make a big difference when people are testing AFDDs.  
BS6004 for PVC insulated and sheathed cables, BS 7211 for thermosetting insulated cables with low smoke and corrosive gas emission, and BS 5467 for thermosetting insulated armoured cables.


Germany introduced mandatory use of Arc Fault Detection Devices (AFDDs) in its national standard DIN VDE 0100-420:2016-02+Amendment A1, effective from December 18, 2017.

Now for the bold.  Search when Germany said that AFDD's did not need to be mandated?  What do the German engineers know that we have yet to experience in the UK?