The fire nobody sees coming
A loose terminal, a nail through a cable or a cracked wire can create an electric arc: a tiny, hot, sputtering spark inside a wall. Arcs rarely trip a breaker — the current stays below the rating — but they easily ignite wood and insulation.
What an AFDD does
An AFDD (arc fault detection device) analyses the high-frequency signature of the current. When it recognises the chaotic pattern of an arc, it disconnects the circuit.
When it is required
Standards recommend AFDDs for buildings made of combustible materials. For a wooden house PlanMyPanel treats AFDD protection as mandatory: wood plus a hidden arc is how houses burn down.