Replace an extractor fan like-for-like

Swap a like-for-like extractor fan safely, checking wiring, ceiling type and circuit isolation before fitting and testing it.

EF-01Turn off the power and check the scope of the jobFind which circuit feeds the fan - it's usually the bathroom light circuit, or has its own fused connection unit. Switch that circuit off at the consumer unit and tape over the switch so nobody turns it back on. Prove the circuit is dead with a voltage tester before touching any wiring.

RULES

1 roll · Electrical tape

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Replacing an extractor fan like-for-like, in the same position on the same circuit, is not notifiable under Part P. If you move it, add a new circuit, or change the fan type, that work becomes notifiable and must be certified by a registered electrician or checked by your council's building control.

EF-02Buy a matching replacement fanTake a photo of the old fan's data label, or the make and model, to a wholesaler or DIY shop. Match the duct size (usually 100mm or 120mm), the voltage, and whether it's a mains fan or a low-voltage SELV fan run through a transformer. If the fan sits within reach of a bath or shower, it needs the same or better IP rating as the old one.

RULES

1 each · Replacement bathroom extractor fan, 100mm

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Fans fitted within bathroom zones 1 and 2 must have an IP rating suited to that zone under BS 7671 (the UK Wiring Regulations). Don't fit a fan with a lower IP rating than the one it replaces.

EF-03Open the fan and photograph the wiringUnclip or unscrew the fan cover to reach the terminals. Before you touch anything, photograph the wiring and label each wire with a bit of tape: permanent live, switched live, neutral and earth. New fans usually follow standard UK colours - brown live, blue neutral, green/yellow earth - but a photo saves guesswork later.

1 set · Insulated screwdriver set

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EF-04Disconnect the wiring and lift out the old fanLoosen the terminal screws and pull the wires free. Undo the fixing screws holding the fan body to the wall or ceiling, then ease it clear of the duct spigot. Keep the old screws to one side in case the new fan uses the same fixing centres.

EF-05Work out what's behind the wall or ceilingRun a stud detector or a strong magnet across the surface: a steady line of screw heads roughly 400mm or 600mm apart marks the joists, battens or studs. Tap between the marks - a dull, solid sound means backing timber; a hollow sound means empty void. Drill a small 3mm pilot hole in an unseen spot: pale dust means timber, fine grey swarf means a metal stud frame. An older, uneven ceiling that feels powdery under a bradawl is likely lath and plaster rather than plasterboard.

EF-06Fix the new mounting points for your wall or ceiling typeCables and pipes can run almost anywhere in a ceiling void, including places you wouldn't expect. Use a cable and pipe detector, but don't trust it alone - it can miss deep cables, cables in metal conduit, or anything behind foil-backed plasterboard, and a metal frame confuses cheap detectors further. Find your stopcock (usually under the kitchen sink) and check it turns, so you can shut off water fast if you hit a pipe. If you have any doubt, isolate the circuit at the consumer unit before drilling, and turn off the water before cutting into anything that could carry water. Solid brick or block: drill a 6mm hole 35mm deep and use a red wall plug with a 40mm woodscrew. Timber joist or stud: drive a 4x40mm woodscrew straight into the centre of the timber, no plug needed. Metal stud: never use a wood screw or plastic plug, it strips straight through 0.5mm steel - use a self-drilling metal-stud fixing or a spring toggle rated for the fan's weight. Dot-and-dab: use a fixing long enough to pass through the plasterboard and adhesive dabs into the masonry behind, typically 50-75mm. Lath and plaster: locate a joist or batten behind the lath rather than fixing into the plaster alone, which will crumble. If the new unit is a heavier inline fan fitted separately in the loft, support it on a noggin or a proper pattress rather than plasterboard alone.

1 each · Cable and pipe detector

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1 pack · Red wall plugs, 6mm

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1 pack · Woodscrews, 40mm

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1 pack · Metal-stud toggle fixing

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1 pack · Dot-and-dab fixing, 6x60mm

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EF-07Reconnect the wiringMatch each wire to the same terminal you photographed earlier: live to L, switched live to SL, neutral to N, earth to E. Tighten every terminal screw firmly and check no bare copper is showing outside the terminal. Fit any timer or humidistat link wire following the new fan's own diagram, if it has one.

EF-08Fit the fan body, connect the duct, and seal the edgePush the duct spigot onto the wall or ceiling outlet and secure it with a hose clip if one is fitted. Screw the fan body onto the fixings from step EF-06, then clip the cover back on. Run a thin bead of frame sealant around the edge where the fan meets the wall or ceiling to stop draughts and stray moisture getting behind it.

1 each · Hose clip

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1 tube · Frame sealant or decorator's caulk

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EF-09Restore power and test the fanRemove the tape from the consumer unit switch and turn the circuit back on. Switch the fan on and check it runs quietly and pulls air - hold a tissue near the grille to feel for suction. Run it for a few minutes and check the cover isn't warm, which would point to a loose connection.

EF-10Tidy up and dispose of the old fanWipe down surfaces and vacuum up any dust from drilling. The old fan contains electrical parts, so take it to a household recycling centre's small electricals bin rather than the bin. Keep the new fan's instructions and any spare fixings in case you need them again.

KNOW THE RULES

Before you start: Which electrical jobs can I do myself? Part P explained

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