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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. :-)

  • 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.

  • 0 in reply to gkenyon

    Lewden are aware of this.  They have found such devices to be problematic with AFDs

  • 0

    This may be worth a watch

    https://youtu.be/VlChmFysT14?si=4IbeZC7bd12FemEz

    It is by David Savery at DSES.  He has done quite a lot of testing into AFDDs and has highlighted many things.  This is about the 5th episode in the series.  His language may be a bit colourful but his content is sound with his impromptu real world testing. 

  • 0 in reply to Sergio Fernandez

    Hi Sergio, Could you please provide more specific details regarding the nature of these problems? I can't see on the thread what you are referring to.

  • 0 in reply to AMK

    Hi AMK

    Sergio Fernandez said:
    Lewden are aware of this.  They have found such devices to be problematic with AFDs

    I was referring to

    power line comms like thoses used in a TP-Link PowerLine, normally used for extending the range of WiFi in the average dwelling. 

  • 0 in reply to Sergio Fernandez

    Interesting to note the effects of spurious RF on these devices. Yet another good reason not to fit. I haven't fitted nor recommended one yet.

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