Extractor Fan Installation in NR15

Three different jobs get called extractor fan installation. A like-for-like swap on the existing cable is usually under an hour. A first fan in a room that has never had one means core drilling the external wall, fitting a sleeve and an outside grille, running the duct, then running a supply. An in-line fan mounted in the loft is different again.

Airflow is set by Approved Document F, not by Part P. A bathroom needs 15 l/s, a utility room 30 l/s, a WC 6 l/s. A kitchen needs 30 l/s with a cooker hood venting outside, or 60 l/s without one. The fan sits no more than 400 mm below the ceiling. A room with no openable window needs a run-on timer of at least 15 minutes, which is why a timer fan needs three cores plus earth and a triple-pole isolator outside the room.

Fans above a bath or shower fall in Zone 1 or Zone 2 of BS 7671 Section 701. IPX4 minimum, with 30 mA RCD protection on every circuit in the room. Replacing a fan on its existing cabling does not need a building control notification.