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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?

Parents
  • 0

    Hey, as you've already taken significant steps in diagnosing the AFDD tripping issue related to the fridge. Given your detailed analysis, here are some further suggestions:

    Load Distribution: If possible, redistribute the load on the circuit to which the fridge is connected. This might alleviate any intermittent current spikes that could be triggering the AFDD.

    Dedicated Circuit: Consider providing a dedicated circuit for the fridge. This can help isolate it from other potential sources of interference or overloading.

    Cable Inspection: Check the cable connecting the fridge for any signs of damage, wear, or loose connections. A damaged cable can lead to intermittent arcs and tripping.

    Positioning: Ensure that the fridge is positioned away from direct sunlight, heat sources, or areas with poor ventilation. Overheating can potentially cause arcs and lead to tripping.

  • 0 in reply to Ashley T Wilson

    Thanks for the detailed reply. But the suggestions are not feasible in an existing installation with a newly fitted expensive kitchen. 

    My only solution was to remove the AFDDs and replace with RCBOs. The manufacturer was not helpful. 

    In the future if I am compelled to install AFDDs then will probably go for Hager as they seem to have the tools via an App to diagnose the fault and update the AFDD if necessary. https://hager.com/uk/p/afdd

  • 0 in reply to sparkiemike

    Nice to see someone is thinking about this - but £100 each is going to make for one expensive CU change!

Reply Children
  • 0 in reply to keylevel

    The cost in terms of time and reputation could be a lot more.

  • 0 in reply to sparkiemike

    Did you do a PAT (Portable Appliance Test) on the fridge?

  • 0 in reply to Sergio Fernandez

    In the original post

    "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."

    so he may not have called it a PAT, but in all but name I think he has.

    Mike.

  • 0 in reply to Sergio Fernandez

    Yes, all tested ok, also visual inspection ok

  • 0 in reply to sparkiemike

    There is an argument that unless you have contractually undertaken to do so, that you assume no responsibility for what the customer plugs into their installation. Same with accessories such as light fittings etc. You simply cannot cater for, nor be held responsible for third party appliances. If the AFDD can't hack it with a fridge, then it's the AFDD maker's problem and should not be yours.

  • +1 in reply to whjohnson

    Unless the cutomer supplied the AFDD, then the installer becomes the retailer of the AFDD so far as the customer is concerned.

    You can't deny responsibility for faults in things you have sold to a consumer.  The consumer has no contract with the AFDD manufacturer, so it's not the manufacturer that their rights are against.

  • 0 in reply to Simon Barker

    I understand that Simon - you have the wrong end of the stick - I was attempting to point out that the actual failure of an item to perform is not the fault of the installer but that of the manufacturer, and that the installer cannot be held responsible for any appliances which get connected to the circuit concerned.

    That said, if these things are so good - or at least as good as their makers claim, then we should be able to relax the requirements for smoke/heat alarms, since those pushing these devices are telling us that there are x no of fires annually that these magic devices will prevent, which is why they wish for us to buy them..

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