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Multiple AFDD’s tripping.

Stuff

Hi all, I wonder if anyone can shed some light on an arc-fault-finding issue?

Installation details:

Large domestic property with a 42-way DB, a large Loxone (home automation) panel with it’s own 24V battery backup. Uniti Power Usymphony SPY300 provides UPS for two circuits (WI-FI & Medical equipment). Install with no issues since May 2023. A Riello SDH 3000 Sentinel Dual 3000VA is providing UPS to a home lift circuit that was added over a month ago.

Eleven Contactum 32A AFDDs are installed on all socket outlet circuits. RCBO’s on all other circuits

The property is located close to a small/medium-sized retail park.

The Problem:

The homeowner called on Monday this week to say that the kitchen electrics had tripped out. She then followed up with messages to say that the annexe kitchen had tripped, then the loft and then the bedroom sockets. All had tripped when appliances were operated. Sometimes a washing machine, toaster, kettle hover, etc. In all, four AFDD circuits tripping randomly.

Fault finding:

The kitchen AFDD stays up, but when I put on the kettle and the toaster the AFDD trips. If the fridge and toaster are on, the AFDD trips.  With the UPS systems removed, it still happens.

I removed both UPS systems before testing.

I tested the kitchen circuit; it was solid, with no issues. Earth leakage at the incomer was 23.55mA; on the kitchen circuit, it was 3.4mA with appliances on standby. I tested all the kitchen appliances under load, and the total leakage was approximately 3 mA. I ramp-tested the AFDD—23mA. I moved the appliances around the property and could see that they were not the problem. So, it was definitely an arc issue. Also, the LED status indicated an arc trip. Continuity tests confirmed no loose connections.

With all other circuits off. I cannot get the kitchen AFDD to trip.

Cause:

I spoke with Contactum technical, who were really helpful, but we couldn’t determine what was tripping the arc device.  Spoke to the NICEIC – they could not provide any support.

The fact that it has been in place for over a year with no issue, could it be a quality of supply issue from Nathoin Gird? The property has had a number of mini power cuts in the past – hence the UPS going in.

Any suggestions?

 

Thanks in advance. :-)

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  • 0 in reply to sparkiemike

    I had a quick scan. It seems that you have had pretty much the same issue – with the same outcome – I’m going back tomorrow to replace the remaining eight AFDDs with RCBOs.

    I’m sure the installation is sound. This means I have an unreliable product tripping because it thinks there’s an ARC fault when there’s not, or there’s an upstream issue causing the devices to trip. I don’t think it’s the former, as it would be highly unlikely for eleven devices to become faulty at the same time. So, it could be the latter, and I have no control over that; I can't test it or prove it.

    If an AFDD can trip due to upstream issues or reading noise on the system as an arc when it’s not, then doesn’t that make the device inherently unreliable? Considering that they are mandated for high-risk properties, doesn’t that then make them potentially… I don’t want to say ‘dangerous’; perhaps ‘risky’?

     As I’ve experienced a fault I can’t trace on a device I can’t test, I won't be recommending them in the future. 120.3 allows for departure, but not sure me stating, “ I had a bad experience with AFDDs once” qualifies JoyJoy

  • 0 in reply to Stuff

    Whoopsie! Time to hit the backspace on my departure box, was hoping to get away with Not installed due to engX forum critics.

  • 0 in reply to AMK

    Joy

    On a serious note, how reliable are these devices in UK conditions? Has anyone carried out a survey/report/study on this? Does anyone install these on mass? Can they provide any feedback on reliability?

  • 0 in reply to Stuff

    If you really cannot get rid of the AFDDs for regulatory reasons, then their enthusiasm for false alarms may at least be partly defeated by low pass filtering to remove ( well spread out and soften really), the arc-like spikes from particularly virulent loads. We are not exactly short of choices of filter shape and spec.

    https://uk.farnell.com/c/passive-components/emc-rfi-suppression/power-line-filters

    Though most are aimed at mounting inside equipment and single phase units tend to be for 16A and below.

    However filters where there is a lot of capacitance L-E cause currents that can lead to RCD tripping so there is no free lunch.

    Sadly, unless you have a truly massive budget, and lots of space, then filtering a high current incoming supply to remove trigger events coming in from off-site is quite impractical - its the sort of thing done at nuclear bunkers but not on domestic supplies. (hence the high  price from the few folk who do make something suitable)

    Mike.

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