Circuit protection
AFDD Requirement & Selection Helper
See where arc fault detection is commonly recommended, which protection architecture fits, and how to specify the device. This is risk-based guidance, not a compliance verdict — whether an AFDD is mandatory depends on the national wiring standard and edition adopted for the project.
How to read this
An AFDD (called an AFCI in North America) detects hazardous series and parallel arcs that an MCB or RCD may not see. It is applied mainly to final circuits where damaged wiring or connections could start a fire without producing enough overcurrent or earth leakage to trip conventional protection. Sleeping accommodation, combustible locations, and premises with irreplaceable contents are where it is most often recommended or required.
The architecture depends on which other functions the circuit needs. Where the circuit also needs residual-current protection — common for socket outlets — an AFDD-RCBO combines arc, overload, short-circuit, and residual-current protection in one device. Where residual-current protection is separate or not required, an AFDD combined with an MCB is used.
Frequently asked questions
Is an AFDD mandatory?
There is no single worldwide rule. It depends on the adopted installation standard and edition, the building use, and the circuit purpose and rating. A client specification, insurer, or documented risk assessment may also require it.
AFDD or AFCI?
AFDD is the IEC term (IEC 62606); AFCI is the North American term (UL 1699, applied per the NEC). They mitigate similar arc hazards but are not automatically interchangeable — match the device to the destination market.
Does an AFDD replace an RCBO?
Only a device explicitly certified as an AFDD integrated with an RCBO provides arc, overload, short-circuit, and residual-current protection together. A standalone AFDD does not — read the certificate scope and markings.
Specify the AFDD
Match the architecture, rating, and RCD type to a device for the destination market.
Risk-based guidance only. The mandatory scope and final selection must be confirmed by a qualified person against the adopted national standard, its edition, and the manufacturer’s datasheet.