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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 Stuff

    Stick with RCBOs only. Replace any existing AFDDs with RCBOs if any faults arise in future. AFDDs are unproven technology and the early adopters are always going to get burnt. Sometimes you have to make a independent engineering judgement rather than blindly following regulations. RCBOs give plenty of protection for new and existing circuits, so nothing negative should arise. AFDD tech is in it's infancy and they are still trying to find out via the guinea pig method as to how far the 'sensitivity slider' should be adjusted in order to function correctly in the real world.

    My guess is that if there is a rush of complaints about  'nuisance tripping, then all they will do is issue a firmware update to 'blind' existing AFDD sensitivity to stop it tripping, thus rendering you  with what will effectively become a RCBO-only in terms of functionality going forward.

  • 0 in reply to whjohnson

    Thanks for the reply. We adapted a house for a chap who became quadriplegic after an accident at work, so I thought it best to provide the safest installation possible. It doesn’t quite fit into the recommendations of 421.1.7, so there is no problem replacing it with RCBOs – which I have done while the existing AFDDs have been sent back for replacement.

    I asked the retailer if they have any problem with AFDDs; they said they wouldn’t know as they’ve only ever sold them to me  Blush

  • 0 in reply to Stuff
    Stuff said:
    We adapted a house for a chap who became quadriplegic after an accident at work, so I thought it best to provide the safest installation possible. It doesn’t quite fit into the recommendations of 421.1.7, so there is no problem replacing it with RCBOs – which I have done while the existing AFDDs have been sent back for replacement.

    Poor chap!

    Concerning 421.1.7, it sounds a bit like a care home for one, so I agree with the sentiment. However, if the AFDDs are tripping when they should not, it may be argued that they are less safe than RCBOs.

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