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How to install a centrifugal bathroom fan

Updated: 21 October 2026

You are replacing a centrifugal bathroom fan, or fitting one on a duct that already leaves the room, and you need to know what finished looks like before anyone opens a terminal. New bathroom wiring, a fan in zone 1, a SELV conversion, a missing permanent live, or a fan that trips or smells hot is a stop. This page describes the outcomes. It does not tell you which core lands on which terminal. The [centrifugal fan comparison](/hub/cooling/centrifugal-fan) is the product table. Peter F. set these checks from public UK guidance and the amazon.co.uk listings on 20 October 2026. There was no install. A qualifying purchase can earn a commission at no extra cost to you.

You are replacing a centrifugal bathroom fan, or fitting one on a duct that already leaves the room, and you need to know what finished looks like before anyone opens a terminal.

Our top picks

Vortice Vortice Ariett T

Best overall

Vortice Vortice Ariett T
9.0/10about £52.50
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Nuaire Nuaire Cyfan

Rank 2

Nuaire Nuaire Cyfan
8.0/10about £146.99
View offer
Manrose Manrose CF200S

Rank 3

Manrose Manrose CF200S
7.3/10about £37.99
View offer
On this page
  1. 1.When to stop
  2. 2.What the extract has to achieve
  3. 3.Timer, permanent live and the windowless room
  4. 4.Zone, IP and the isolator
  5. 5.Using it afterwards

When to stop

Switch the fan off at the isolator, and leave it off, if you smell burning, see arcing, or the breaker trips. Electrical Safety First says to use a registered electrician to select, fit and replace an extractor, and to stop on a burning smell, arcing, or a tripping breaker. A like-for-like swap still sits inside that advice. Call an electrician for new bathroom wiring, a 230 V fan in zone 1, the Nuaire’s SELV conversion, and a timer that needs a permanent live the ceiling rose does not provide. Call a competent person for a building-control airflow measurement. This page does not decide which jobs are notifiable under Part P. The overrun times below are England’s rule. You can still check discharge, duct sag and the isolator. Those checks are not a licence to wire the fan.

What the extract has to achieve

The fan has to discharge outside. Recirculating into the loft is not extract. The terminal should be as high as practicable and at most 400 mm below the ceiling. A duct in a cold loft should be insulated, and it should not sag between joists. A sag becomes a water trap, and that water runs back into the fan. Horizontal duct should fall so moisture does not drain into the scroll. Flexible duct left long and crushed is the usual way a sticker litre figure disappears. The Vortice states 19.4 litres per second. Manrose’s range page is about 31 litres per second, which the amazon listing does not print. The Nuaire manual says up to 60 litres per second on a short through-wall duct. None of those numbers is the installed test. Compare the claims in the centrifugal fan buying guide before you buy.
Vortice Vortice Ariett T

Testsieger

Vortice Vortice Ariett T
9.0/10about £52.50
View offer

Timer, permanent live and the windowless room

In England, a room with no openable window needs the fan to keep running for at least 15 minutes after you leave. The Vortice timer runs from 3 to 20 minutes, so 15 minutes or more meets that figure and 3 minutes does not. It works only with permanent live, switched live and neutral. B&Q’s note for model 11976 says the timer cannot be used without those three wires. One review says you can omit the overrun if there is no permanent live. The fan then stops with the light. If the room needs the overrun, that missing live is the moment you ask an electrician. A fan that never stops is a different fault. Do not open the wiring unless you are qualified. The Manrose CF200S does not state a timer. If the room is windowless, that listing was the wrong buy. The best centrifugal bathroom extractor fan page is why the Vortice is the timer fan in this set. Landing the Nuaire’s controls stays with the electrician.

Zone, IP and the isolator

Zone 0 is inside the bath or tray, zone 1 is above it, and zone 2 is 0.60 m beyond. A suitable 230 V fan may be in zone 1 or 2 if it is at least IPX4. The overrun isolator is triple-pole and sits outside those zones, with a 30 mA RCD. The Vortice states IPX4. The Nuaire manual states IPX4; the amazon field is blank. The blowers state no IP rating. Do not put mains onto the 12 V fan leads. The centrifugal vs axial extractor fan page matters only if you are still choosing the mechanism.

Using it afterwards

Once it is in, keep the intake clear. Electrical Safety First notes that a clogged grille is how a fan overheats. Clean the cover with the isolator off, and let a timer fan finish its overrun. If it runs all night, that is a wiring or humidistat fault. A 12 V blower kit is not installed as a bathroom extract. If the bathroom fan smells hot after the clean, stop and call the electrician.

Common questions

Can I replace a centrifugal bathroom fan myself?
Electrical Safety First says to use a registered electrician to advise and to carry out installation or replacement. A like-for-like swap is still their electrician job. You can check discharge, duct sag, overrun and the isolator position. You should not open terminals, add a permanent live, or convert a fan to SELV yourself.
Where must the fan and the isolator sit?
A 230 V fan in zone 1 or zone 2 needs at least IPX4. The isolator for a windowless fan, and a triple-pole overrun isolator, sits outside zones 0, 1 and 2. Zone 0 is inside the bath or tray, zone 1 is above it, and zone 2 is 0.60 m beyond. If you cannot place the isolator outside those zones, stop.
Why does a timer fan need more than the light switch?
The overrun needs a permanent live as well as switched live and neutral, so the fan can keep running after the light goes off. The Vortice’s 3–20 minute timer cannot do that job without those three connections. Wiring it to the light only means it stops when the light stops.
What do I do if it smells hot or trips?
Switch it off and stop. Electrical Safety First names burning smell, arcing and a tripping breaker as the point you cease use and get a registered electrician. Do not reset the breaker and try again to see if it was the steam.
Who measures the litres per second?
A competent person, if building control or your designer needs an installed figure. The numbers on the Vortice, Manrose and Nuaire pages are claims. They are not the test. Call that person rather than treating 19.4 litres per second as the result after a long duct.

Related pages

Centrifugal blower fan for a BBQ

Centrifugal fan

Best centrifugal bathroom extractor: Vortice Ariett T

Centrifugal fan buying guide: extractor or 12 V blower

Centrifugal vs axial extractor fan for longer ducts

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these listings were read on 19 October 2026. Page updated 20 October 2026.

  1. Approved Document F volume 1, 2021 and 2026 PDFs — rates, height, overrun, future duct rules (retrieved 2026-10-20)
  2. BEAMA Part F bitesize guide — 15 l/s, short flexible duct, 0.5 W/(l/s) (retrieved 2026-10-20)
  3. Domus Ventilation — axial about 1.5 m, centrifugal about 6 m, Part L note (retrieved 2026-10-20)
  4. Which? bathroom extractor buying guide — axial versus centrifugal (retrieved 2026-10-20)
  5. IET Wiring Matters BS 7671 FAQ — IPX4 in zones 1. (retrieved 2026-10-20)
  6. SELECT bath and shower pocket guide — zone sizes (retrieved 2026-10-20)
  7. Manrose CF200S page — 110 m³/h, about 31 l/s, IPX4, standard model (retrieved 2026-10-20)
  8. Nuaire Cyfan manual — 24 V motor, SELV, up to 60 l/s (retrieved 2026-10-20)