Domakihub Wire a Bathroom Fan to the Light Circuit: A Clear Guide
Understand how the wiring works, what to prepare, and when to call a licensed electrician.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A bathroom extractor fan that runs off the same light switch is one of the most common small electrical jobs in Greek homes, holiday rentals, and hotel rooms — yet it is also one of the most frequently left half-done or wired incorrectly. The video above shows both the single-switch and dual-switch configurations in detail. This article walks you through how the circuit works, what decisions you need to make before any cable is touched, and — crucially — why this job must be handed to a licensed electrician (ηλεκτρολόγος) for any work on mains wiring.
Why the Light Circuit Is the Natural Feed for a Bathroom Fan
In most Greek bathrooms the lighting circuit is already routed to a ceiling rose or junction box directly above the shower or bath zone. A bathroom extractor fan needs a permanent live feed (L), a neutral (N), and an earth (E) — exactly what the light circuit carries. Tapping the fan from this circuit avoids running a new cable back to the consumer unit and is widely accepted practice, provided the circuit is not already close to its rated load.
One important caveat: Greek electrical regulations (based on IEC 60364 and ELOT HD 384) define humidity zones inside bathrooms. Zone 1 is directly above the bath or shower tray; Zone 2 extends outward. Equipment must carry an IP rating appropriate for its zone. Most ceiling-mounted fans are rated IP44 or IP45, which is sufficient for Zone 2 and the outer boundary of Zone 1 — but always check the fan's datasheet before buying.
Single Switch vs. Dual Switch: Choose Before You Wire
The most common layout in older Greek apartments is a single switch that controls both the ceiling light and the fan together — simple, low cost, and compliant as long as the switch is outside the bathroom door or in a permitted location within the room. The drawback is that the fan stops the moment the light is turned off, which may not give enough extraction time after a shower.
A dual-switch or timer-relay arrangement lets the fan run independently or for a set period after the light is switched off (typically 5–15 minutes). This requires either a two-gang switch or a dedicated fan timer module wired in line. Decide which configuration you want before your electrician visits — it affects the cable route and the switch box depth.
How the Job Is Done (Step by Step)
- 1
Isolate the circuit at the consumer unit
Before any work begins, the electrician switches off the correct MCB (miniature circuit breaker) for the bathroom lighting circuit and verifies with a voltage tester that the circuit is dead at the ceiling rose or junction box. Never assume the light being off means the cable is safe — the line conductor is always live unless the breaker is open.
- 2
Access the existing ceiling rose or junction box
The junction point for the bathroom light is opened carefully. The electrician identifies the line (live), neutral, and earth conductors and notes how many cables are already in the box. In older Greek installations this may be a simple twist-and-tape joint rather than a proper connector block; part of the job is often upgrading this to a rated connector (e.g. Wago 221) at the same time.
- 3
Run a cable from the junction point to the fan position
A new 3-core (L/N/E) cable — typically 1.5 mm² for a standard fan drawing under 50 W — is routed from the junction box to the fan's mounting position on the ceiling. In a tiled bathroom this often means running the cable inside conduit above the ceiling plasterboard or through the cavity. The cable route must avoid penetrating the shower enclosure itself.
- 4
Connect the fan (single-switch or timer configuration)
For single-switch operation, the fan's live terminal is wired to the switched live (the wire that goes to the light fitting), so both the light and fan share the same switch. For a timer or dual-switch configuration, the fan receives its own switched live from the second switch, while still sharing the neutral and earth from the same circuit. The fan's earth wire is always connected — never omitted.
- 5
Restore power and test
With all covers replaced and the fan secured to its mounting bracket, the MCB is switched back on. The electrician verifies that the light and fan both respond as expected from their respective switches, checks that no RCD trips occur (which would indicate an earth fault), and confirms airflow through the external duct. A label is added to the consumer unit if the circuit label was unclear.
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FAQ
- Can I wire the bathroom fan myself to save money?
- In Greece, any work on fixed mains wiring — including tapping a new spur from a lighting circuit — must be carried out by a licensed electrician (ηλεκτρολόγος with an ΕΓΝΑΤΙΑ or equivalent qualification). Beyond the legal requirement, bathroom wiring is particularly hazardous due to the combination of water and electricity; an incorrectly wired fan in a humid environment can cause fatal shock or fire. Use a professional and ask for a written handover record.
- What if the fan and light are currently on the same switch and I want to separate them?
- Your electrician needs to pull a two-core (plus earth) cable from the existing single-gang switch position to a new two-gang switch box, and confirm the existing junction box can support the additional connection. It is often done at the same time as replacing an old fan, since the ceiling is already open. Budget approximately one to two hours of labour for a straightforward separation job.
- My holiday rental fan makes a humming noise and runs slowly — is this a wiring problem?
- A humming or slow-running fan usually points to a failing capacitor inside the fan motor, a loose connection causing voltage drop, or an undersized cable feeding a fan that draws more current than the original wiring was sized for. Ask your electrician to measure the voltage at the fan terminals while it is running; anything significantly below 220 V suggests a resistance problem in the wiring rather than a faulty fan.