What is an Arc Fault & AFDD

Arc Fault Detection Devices use digital electronics to analyse the waveform of an AC circuit to detect arc faults. The device continuously monitors the circuit for different variations including the duration of an arc and the waveform. Once the device detects an irregular fault the device trips and disconnects the circuit, reducing the chance of it over heating and potentially causing an electrical fire.

AFDDs are recommended to be fitted in consumer units or distribution boards in premises with sleeping accommodation, locations where there is a risk of fire due to the activity within, premises constructed of combustible materials, fire propagating structures such as high rising buildings and locations where there are irreplaceable goods. See regulation 421.1.7 for further details. The regulations state AC single-phase circuits not exceeding 230V, that includes ring circuits, radials etc. mainly focussing on circuits where white goods appliances are present.

There are two types of arc faults that may occur. ‘Parallel’ arc faults are found with damage caused to insulation which allows current to flow between conductors, usually between phase and neutral. Alternatively, ‘Series’ arc faults are found in loose terminal connections, damaged cords or frayed/damaged conductors. These arcs are created in one conductor only, either phase or neutral.

Potential causes of arc faults could include trapped or damaged cables, loose terminations, cable wear or damage caused by construction work.