AFDD Q and A

The product standard for AFDDs states, in the scope:

These devices are intended to mitigate the risk of fire in final circuits of a fixed installation due to the effect of arc fault currents that pose a risk of fire ignition under certain conditions if the arcing persists.

(my highlight).

Regulation 421.1.7 in BS 7671:2018+A2:2022 also relates to a provision for specific final circuits (and talks about the 'circuit to be protected') rather than, for example, Regulations 411.3.3, 708.415.1, 709.531.2, etc, which require RCDs to be provided for socket-outlets (not final circuits supplying socket-outlets).

lyledunn said:

Were that to be the case, then what about all the other circuits that do not have sockets?

Therefore, this is a really good question.

The definition of a final circuit (and circuit) doesn't necessarily imply that circuits (or the effect of their protective devices) stops at accessories, connection units, or socket-outlets, and plugs and socket-outlets can be used for connection of fixed equipment (or portable or mobile) current-using equipment to circuits.

The product standard for AFDDs states, in the scope:

These devices are intended to mitigate the risk of fire in final circuits of a fixed installation due to the effect of arc fault currents that pose a risk of fire ignition under certain conditions if the arcing persists.

(my highlight).

Regulation 421.1.7 in BS 7671:2018+A2:2022 also relates to a provision for specific final circuits (and talks about the 'circuit to be protected') rather than, for example, Regulations 411.3.3, 708.415.1, 709.531.2, etc, which require RCDs to be provided for socket-outlets (not final circuits supplying socket-outlets).

lyledunn said:

Were that to be the case, then what about all the other circuits that do not have sockets?

Therefore, this is a really good question.

The definition of a final circuit (and circuit) doesn't necessarily imply that circuits (or the effect of their protective devices) stops at accessories, connection units, or socket-outlets, and plugs and socket-outlets can be used for connection of fixed equipment (or portable or mobile) current-using equipment to circuits.