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Tackling AFDD Tripping

sparkiemike

How are people tacking AFDD tripping?

In the past if I had a call out for a tripping RCD/RCBO or MCB there are well established procedures and tools to track down the fault.

These range from the visual inspection, insulation resistance testing, earth leakage measurement, RCD ramp testing and RCD time testing. It would not take too long to track down the fault whether it was faulty appliance, water ingress, damaged cable or even a duff protective device. The repair might have taken a bit longer but at least you knew where the fault was.

I had a call out this weekend for a AFDD that was tripping on a ring circuit. The new consumer unit (with 3- AFDDs, RCBOS and surge protection) has been in service the end of November and no issues reported. The customer did his own diagnosing and suspected the fridge/freezer as the circuit stopped tripping when he removed the appliance from the circuit. However, when he plugged the fridge/freezer in to another ring circuit with AFDD protection via a extension lead on a reel it did not trip. At this point I did not know what type of fault it was as the customer did not make a note of LED status on the AFDD.

The fridge has no damage and continuity and insulation resting testing all OK

Ring circuit was intact and insulation testing OK (greater than 500Mohm). The instrument readings were exactly the same as they were at the end of November. Plugged it back in and no tripping. I also ran a 1.8kW load on the same socket for a few minutes to see if I could get it to trip -  all OK.

Ten minutes after leaving the circuit tripped, I returned and from the flashing light sequence on the AFDD it was definitely an ARC fault. Reset the breaker and is was tripping regularly every few minutes.

I plugged in the fridge into another circuit, but this time with my much shorter extension lead. Then proceeded to inspect all sockets and checking tightness of terminals - no issues. Although there are some terminations not accessible for inspection.

Then I noticed the other circuit tripped (with fridge connected via extension lead) - so the conclusion that it is definitely the fridge. As the fridge/freezer is still under warrantee I advised the customer to contact the manufacturer. He plugged it into the original circuit in the hope to keep it running. It did not and I told him again to not run the fridge.

Later that night I get a message that now the other circuit is tripping every time they use the microwave -  not the circuit with the fridge and apparently fridge not plugged in.

At the moment I am not 100% sure it is the fridge and can't rule out a faulty AFDD or has the faulty fridge caused the  microprocessor in the AFDD to go faulty.

As a last resort I told them to switch off all circuits and main-switch and then switch-on one by one. Thinking that these devices have microprocessors maybe they need a restart every now and again - bit like my router at home.

Any suggestions on diagnosing ARC faults?

  • 0 in reply to Sergio Fernandez

    This one 

    note that, as  with all Dave Savery Videos ,his language is not suitable for those of a sensitive disposition,
    or minors, or indeed any one  who works underground.

    Putting that to one side, and the fact it is rather long,  technically I find the content is fascinating, if quite worrying.
    'Nothing wrong with relying solely on inadeqauetly tested software'  has not panned out well for the Post Office or  Fujitsu recently, and I think  it may not do so for Hagar either.


    Mike.

  • 0 in reply to mapj1

    Hi Mike

    Thats the video yes.  The language is colourful but I think the facts he brings up are very valid.  Like the Hagar test device that goes in the CU.  The fact there is still no firmware update despite the fact that people are reporting issues to Hagar.

    Should a fire arise from a Hagar AFDD not working correctly there will need to be a firmware update rolls out or possible a factury recall of all their (Smart) AFDD devices.

  • 0 in reply to Sergio Fernandez

    Should a fire arise from a Hagar AFDD not working correctly there will need to be a firmware update rolls out or possible a factury recall of all their (Smart) AFDD devices.

    I suspect that'll never happen - after all how could anyone demonstrate that the fire would really have been prevented if the AFDD had behaved differently? The fire may have been started by simple resistive heating at a bad joint or a conductor thinned by damage m'Lud - without any significant arcing being present - which of course no AFDD could ever reasonably be expected to detect. Prove otherwise their highly paid lawyers will say.

       - Andy.

  • 0 in reply to AJJewsbury

    Did you watch the video Andy?  Do you think that David at DSES has some valid points about the Hagar AFDD?

  • 0 in reply to Sergio Fernandez

    I saw the earlier one, and have skimmed the latest - yes there are questions I'd like answered. These big companies though are primarily there to make money for their shareholders - recalls or similar mass updates cost a fortune, so unless their position becomes indefensible they'll not spend the money. As long as they pass the tests required by EN 62606 or whatever (which I presume they do) I'm sure their lawyers will be telling them they're on safe legal grounds, whatever a bloke with a bit of lego and brass (or carbon) fittings comes up with.

    Nothing's perfect - it's reckoned around 7% of in service RCDs don't trip when the should, 'when they should' doesn't include lots situations that have residual d.c. currents - and even then there's 5% of the population that are aren't covered for shock protection.

       - Andy.

  • 0

    It is really unfortunate that it would appear that the Hager devices are not working under the DSES testing process. I don't think Hager have tackled this problem head-on and this undermines their credibility - even for me as I really like the Hager kit.

    The problem of diagnosing AFFD tripping still remains. I am not aware that any other manufacturers have a solution. In the dark sea of nothingness of AFFD testing the Hager solution was a glimmer of light - unfortunately the light is vanishing quickly. 

  • 0 in reply to sparkiemike

    I agree with you there that Hager kit is normally very good.  It is just the AFDD offering that is not up to muster.

  • 0 in reply to mapj1

    There is another follow up video from David.S at DSES on AFDDs

    Titled

    AFDD: Rig MK III and an all-star line up

    https://youtu.be/CZtSsFBr4K8?si=tgX6ZToSZ73eV43C

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