Wiring a bathroom extractor fan: what you can do yourself

Which part of the job is ordinary DIY

Removing the old fan, cleaning out the housing, and fitting the new unit into the existing hole is straightforward mechanical work. Most extractor fans are held in with two or four screws or a simple clip mechanism, and if you are replacing like-for-like, the opening in the wall or ceiling is already the right size.

Ducting is the same story. If the duct run to the outside wall or shared ventilation shaft already exists, checking it for blockages, cleaning it out, or swapping a perished flexible hose for a new one is well within reach of someone with basic tools. A stiff brush, a new length of ducting, and some foil tape usually see to it.

Where people run into trouble is assuming that because the mechanical part went smoothly, the wiring will too. It often looks simple: two or three wires going into a terminal block. Looks are misleading here, and that is the part covered next.

Why the electrical connection is left to an electrician

A bathroom is classed as a wet zone, and the areas around a shower or bath have specific requirements for what kind of fittings and connections are allowed, and how they must be protected. An extractor fan sits inside or close to that zone more often than not, particularly in smaller Estonian bathrooms where the ceiling fan is a metre or so from the shower.

Getting the earthing, the circuit protection, or the fan's own IP rating wrong is not something you would necessarily notice straight away. The fan might run perfectly well for months before a fault shows up as a nuisance trip, or worse, as a shock hazard in a room where people are wet and often barefoot.

This is also why we do not try to talk customers through the wiring over the phone. Connecting the fan to the circuit, choosing the right protective device, and making sure the installation meets the requirements for a wet zone is electrical work, done by a qualified electrician, from 49 € per hour.

Pull-cord, wall switch, or timer — what changes at installation

A pull-cord fan is wired directly and switched from inside the bathroom by the cord itself, which keeps the switching mechanism inside the wet zone but built into a sealed unit designed for it. Mechanically this is usually the simplest fan to fit, since there is no separate switch to position or wire back to.

A wall-switch fan, whether it runs off its own switch or is linked to the light, needs a cable run from the fan to a switch mounted outside the wet zone, typically by the door. If that cable route does not already exist, this becomes more work than a straight swap, and it is exactly the kind of routing an electrician should plan and carry out.

Timer and humidity-sensing models add a small control unit, either built into the fan or mounted separately, that keeps the fan running for a set period after the light goes off or moisture drops. The mounting is no different, but the wiring has an extra connection and, on some models, settings to configure correctly, which is worth having checked at the same time as the main connection.

The most common mistake when replacing a fan

The mistake we see most often is buying a new fan without checking the duct diameter and airflow rating against the old one, then finding it does not sit in the existing hole or does not move enough air for the room. A bathroom with no window relies entirely on the extractor to manage moisture, so an undersized replacement can leave you with condensation and mould problems that the old fan, however tired, was not causing.

The second common mistake is reusing old wiring or a terminal connection without having it checked, on the assumption that if the old fan worked, the same connection is fine for the new one. Fans vary in their power draw and wiring configuration, and what suited one model is not automatically right for another.

• Measure the old duct diameter before ordering a replacement fan
• Check the airflow rating (l/s or m³/h) suits the room size, not just the fan that was there before
• Do not assume old wiring or a terminal connection is automatically compatible with the new unit
• Confirm the IP rating matches the fan's position relative to the shower or bath
• If the fan is linked to the light or on a timer, check the switch wiring before removing the old fan

When to stop and call an electrician

If the new fan needs a wall switch where there was previously only a pull cord, or if you are adding a timer function that needs a new control wire, stop before touching the circuit. Running new cable in a bathroom, especially through a wet zone, is where the job needs a qualified electrician.

The same goes if the existing wiring looks old, discoloured, or is not clearly labelled, or if you are not confident about which cable is live once the old fan is off the wall. Guessing at this stage is how straightforward jobs turn into repairs.

For the mechanical work, taking the old unit down, cleaning or replacing ducting, and holding the new fan in place ready for connection, our odd jobs service from 39 € per hour can take care of it, with the wiring itself handed to an electrician for the final connection and test.