Domakihub Install a PIR Sensor for Indoor Lights: A Practical Guide
Understand how ceiling and wall PIR occupancy sensors work, what your electrician will do, and how to prepare for the job.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A PIR (passive infrared) sensor automatically switches lights on when someone enters a room and off again after a set delay — saving energy, adding convenience, and reducing wear on switches in busy corridors, stairwells, bathrooms, or storage rooms. The video above walks through a real ceiling PIR installation so you can see exactly what the job looks like; this guide gives you the ordered steps, key decisions to make in advance, and clear guidance on which parts require a licensed electrician. In Greece, mains wiring work must be carried out by a registered electrical contractor (ηλεκτρολόγος εγκαταστάτης) in compliance with ELOT HD 384 and accompanied by an updated installation declaration (Υπεύθυνη Δήλωση Εγκαταστάτη).
What is a PIR sensor and how does it work?
A passive infrared sensor does not emit anything — it reads the difference in infrared heat between a moving body and the ambient background. When a person crosses the detection zone, the sensor triggers a relay that powers the lights. Most residential sensors combine three adjustable settings: sensitivity (how much movement is needed), time delay (how long the light stays on after the last movement), and a daylight lockout dial (lux) that prevents the light from firing in already-bright rooms.
Ceiling models typically cover 360 degrees and are ideal for rooms up to about 12 m² per sensor head. Wall-mount models have a narrower field — often 180 degrees — and suit corridors, entrances, and staircases where the walking direction is predictable.
When you need a licensed electrician (and when you may not)
Any work that involves opening a junction box, cutting into existing cables, or connecting directly to the mains circuit is mains electrical work. In Greece this is legally reserved for a licensed electrical contractor. Attempting it yourself invalidates home insurance, voids building compliance certificates, and creates real shock and fire risk. If the sensor replaces an existing ceiling light fitting and the new unit is self-contained (plug-in or low-voltage lamp-holder type), some handyman replacements are possible — but when in doubt, call a professional.
There is still a lot you can do yourself to prepare: choose the right sensor type, decide on placement, check whether your existing wiring has a neutral at the switch position (many older Greek installations do not, which affects which sensor model works), and communicate clearly with your electrician so the job is quick and well-quoted.
How a licensed electrician installs a ceiling PIR sensor — step by step
- 1
Switch off the circuit and verify it is dead
The electrician isolates the correct lighting circuit at the distribution board and confirms the circuit is dead with a non-contact voltage tester before touching any wiring. In a shared property or hotel this step also involves notifying other occupants, since lighting circuits often serve multiple rooms.
- 2
Choose the mounting position and check the ceiling void
The sensor goes in the centre of the room's ceiling for 360-degree coverage, away from air-conditioning vents (which cause false triggers), skylights, and direct sunlight. The electrician checks what is above — concrete slab, suspended ceiling, or timber — to select the correct fixings and to confirm cable can be routed without disturbing adjacent wiring.
- 3
Connect Live, Neutral, and Switched-Live terminals
Most mains PIR sensors have three terminals: L (incoming live from the board), N (neutral), and L1 (switched live out to the light fitting). The electrician terminates all three using appropriate connectors inside the ceiling back-box, matching the sensor wiring diagram. If the existing switch-drop does not carry a neutral — common in older Greek installations — the electrician may need to run a new twin-and-earth cable from a junction box that does.
- 4
Set sensitivity, time delay, and lux threshold
Before closing the cover, the electrician adjusts the three dials on the sensor body. Sensitivity is typically set to medium for indoor residential use. Time delay is set to the shortest practical period — 1 to 2 minutes for a corridor, up to 5 minutes for a bathroom. The lux dial is set so that the sensor is inactive in daylight, saving energy during the day.
- 5
Test, label the circuit, and issue the compliance declaration
With the circuit restored, the electrician walks through the detection zone to confirm the lights trigger correctly and time out as expected. They also confirm the manual override (if fitted) works. Finally, the electrician updates the installation declaration (Υπεύθυνη Δήλωση Εγκαταστάτη) to record the new fitting — a legal requirement in Greece for any alteration to a fixed electrical installation.
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FAQ
- Can I install a PIR sensor myself in Greece?
- Low-voltage, battery-operated, or plug-in sensor lights can generally be fitted by the homeowner. However, any work involving the mains supply — opening junction boxes, connecting to existing cables, or replacing a hardwired ceiling fitting — must be carried out by a licensed electrical contractor (ηλεκτρολόγος εγκαταστάτης) under Greek electrical installation regulations (ELOT HD 384). Unlicensed mains work can also invalidate your home insurance policy.
- My old wiring has no neutral at the switch. Can I still add a PIR sensor?
- Many older Greek properties were wired with switch-drops that carry only the live and switched-live, with no neutral. Standard PIR sensors need a neutral to power their electronics. Your electrician has two options: run a new cable that includes a neutral, or fit a 'no-neutral' (two-wire) PIR module specifically designed for this situation. The latter works with most LED loads but may cause flicker with very low wattage fittings, so discuss lamp compatibility before choosing.
- How long does a PIR sensor installation typically take?
- A straightforward replacement of an existing ceiling light with a PIR sensor unit usually takes a licensed electrician one to two hours per fitting, including isolation, wiring, adjustment, testing, and paperwork. If new cable needs to be run — for example to add a neutral where none exists — allow half a day. Booking a Domakihub electrician with the fitting model already chosen will keep the job as short as possible.