Schemes

Bathroom Extractor with Overrun

Fan runs with the light; timer keeps it running after switch-off.

ISOFAN
● Line● Neutral● Earth

Tap any wire, switch or device to see what it is.

Isolator
Light switch

Useful Information

Fan gets permanent L, N and a switched live from the light. The 3-pole isolator breaks all three for maintenance.

When the light goes off, the timer runs the fan for a set time.

Important to know

  • Bathroom: 30 mA RCD on all circuits (701.411.3.3).
  • Equipment in zone 1 must be at least IPX4 (701.512.2).
  • Isolator must disconnect all poles including the switched live.

BS 7671:2018+A4:2026 references

701.411.3.3701.512.2537.3

Study notes paraphrased — check against your copy of BS 7671.