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Posted By Topic: Arc Fault Protection Domestic

Mar 15 2020 14:27

Hi All

I am a sparky of many years.
I read about AFDDs a few years back in the Electron mag (long gone) but I cant seem to find much NZ info even on the Schnieder (PDL NZ) site on using these.Other than US videos.
I know they have been in NZ for a few years now but I admit I haven't used any yet.
And I know they are mandatory in other countries like the USA.

Based on the limited stocks and sales through the wholesalers, their relatively high price and the lack of existing boards I've seem out there with them in to date, I assume they are not widely used yet unless they become mandatory?

I do believe that its safety first so I want to get schooled up as quickly as I can and for a start use them on my own house as I'm upgrading as a learning curve.

Also its seems they can only be used one per circuit.

Does that mean if you have 20 ccts you need 20 AFDDs.... very expensive !!!!

Any comments or ideas? Thanks

Mar 15 2020 16:18

People don't tend to install things like that unless mandatory - $$$.

The US also appears to have had a *lot* of issues with nuisance tripping, so I would not want multiple circuits per AFDD for the same reasons as RCDs being limited to 3x circuits. Motors appear to be especially troublesome - do not put a fridge on one.

3000:2018+A1 has some requirements for their use, and Appendix O. These are of course not mandatory yet.

I think one the other areas suggested was bedrooms, as furnishings tend to be close to sockets.

If you were going 'above and beyond', I think sockets in bedrooms, attic, garage, and any workshop space would be reasonable. Don't worry about kitchens, laundries, more open areas etc., or any lighting.

This should sum to perhaps 5.

Note that the US has a number of risk factors we don't regarding arcing:

* Widespread use of 'backstab' spring-contact terminals, notorious for failing.

* Non-insulated plug pins so anything dropped across the top of a plug gets line voltage.

* Single-insulated flexible cable is more susceptible to damage.

* Lower voltage means higher load currents.

* There may not be enough fault current to operate MCBs immediately on a hard fault.

Mar 15 2020 16:27

The Are detection devices used in the US are a completely different type of operation used in Europe and in NZ.

Typing in AFDD in Google will get the AFDD date sheets of the types used in NZ if you follow the maker Schneider website

Mar 15 2020 19:07

I upgraded a whole house and havent had any problems with nuisance tripping so far.

Also i emailed the insurance council of NZ with regard to protecting old wiring and received this back

"Hi Toyoto. We believe the use of arc fault detection devices will become mandatory in Australia and New Zealand in the near future. Insurers support the use of these devices. However they do not see it as a substitute for fixing dangerous wiring. Generally, insurers look for houses which are pre-1945 to be rewired. The old wiring is generally brittle and deteriorated to the extent that it can cause house fires. Insurers data shows that a large number of building fires start from old wiring and AFDDs would not be a substitute for replacing this. The insurance industry does however support the mandating of these devices in electrical standards for protection of lives and property."

Mar 16 2020 08:39

I expect AFDDs will follow a path similar to RCDs. Few installed until made mandatory, and then as more are installed the price will come down.

There are AFDDs that offer both arc detection and overcurrent functions - similar to an RCBO having 2 functions. Schneider's version (ex Europe, used for NZ field trials) is limited to 25 A; and what they've made available for NZ market is a single-function device.

There are several other suppliers with AFDDs available, though not necessarily sitting on the shelf at your local supplier. At least some, possibly all, include an RCD function; but at fire-protection level (100 -300 mA) rather than shock protection level.

Would maybe be nice to get all three functions (overcurrent, AFDD, & 30 mA RCD) in one unit; but that's a lot of stuff to squeeze into a small package, while ensuring it all works reliably.

I've installed several 25 A units protecting 2 circuits, each with own overcurrent protection. Only issue has been one "trip" on a circuit supplying a washing machine.

The response from Insurance Council is interesting. Clearly they still don't accept (or don't want to admit) that not all old cabling is dangerously deteriorated.
Their support for AFDDs being made mandatory indicates they believe in the technology - but seemingly not enough to trust it.

Mar 16 2020 10:43

Apart from the nuisance risk of loosing the whole supply, why can't one be fitted to the incoming supply before the distribution CBs/RCD's?

Mar 16 2020 11:52

Just a matter of finding one with a high enough current rating.