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Arc Fault Detection Devices

Former Community Member
Former Community Member
Hi Everyone,

I'm just wondering how everyone is faring with AFDDs, especially in commercial/industrial installations?

421.1.1 states that you shall protect against "insulation faults or arcs, sparks and high temperature particles", yet 421.1.7 only recommends AFDDs,


What are everyone's thoughts?


Thanks,

Nathan
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    AFDDs cannot detect a serial fault in an RFC, as the nature of the RFC does not propagate an arc at a loose connection.  Thus, an AFDD would only react to a parallel fault in an RFC installation, which a fuse, MCB and/or RCD will most likely disconnect anyway.  So, not much appeal to fit an AFDD for an RFC.



    Although to be fair, arcing can still occur in spurs from ring finals - and probably more significantly - in things plugged into sockets (appliances, flexes, extension leads...). So a AFDD might still have some benefit, especially (if I understand correctly) as far more fires are started by things after the socket than by fixed wiring.


      - Andy.
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    AFDDs cannot detect a serial fault in an RFC, as the nature of the RFC does not propagate an arc at a loose connection.  Thus, an AFDD would only react to a parallel fault in an RFC installation, which a fuse, MCB and/or RCD will most likely disconnect anyway.  So, not much appeal to fit an AFDD for an RFC.



    Although to be fair, arcing can still occur in spurs from ring finals - and probably more significantly - in things plugged into sockets (appliances, flexes, extension leads...). So a AFDD might still have some benefit, especially (if I understand correctly) as far more fires are started by things after the socket than by fixed wiring.


      - Andy.
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