Domakihub How to Install a Photocell for Outdoor Lights
Understand how dusk-to-dawn sensors work, what the job involves, and when to call a licensed electrician in Greece.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A photocell (light-dependent sensor) turns outdoor lights on automatically at dusk and off at dawn — a practical feature for homes, holiday rentals, and hotel entrances across Greece where security lighting runs through long summer nights. The video above by Fort Knox Co. shows the wiring steps hands-on; this article walks you through how the job works, what a licensed electrician will do, and how to prepare so the visit goes smoothly. Because photocell installation involves working on mains-voltage wiring, Greek law (Presidential Decree 108/2013) requires the work to be carried out by a licensed electrical contractor — this guide is written to help you understand the job, not to replace a professional.
What Is a Photocell and Why Install One?
A photocell — also called a photoelectric sensor or dusk-to-dawn switch — contains a light-sensitive resistor (LDR) whose electrical resistance drops as ambient light increases. When daylight fades below a set threshold, the sensor closes the circuit and switches the connected light on; when morning light returns, it opens the circuit and the light turns off automatically.
For holiday rentals in the Cyclades or hotel car parks in Crete, this means guests always arrive to a lit entrance without anyone needing to flip a switch. It also reduces energy waste compared to leaving lights on a timer that does not adjust for seasonal daylight shifts.
Types of Photocell Available in Greece
The most common type found in Greek electrical supply shops (ηλεκτρολογικά) is the twist-lock NEMA photocell, which plugs into a matching socket on a wall lantern or area floodlight. A second type — the inline or in-line series photocell — is wired directly into the live (phase) wire of the circuit inside a junction box or within the fitting itself. A third variant is the integrated dusk-to-dawn bulb, where the sensor is built into the lamp cap and no extra wiring is needed at all.
For a simple single-fixture swap, twist-lock sensors are the easiest for an electrician to fit. For controlling multiple luminaires from one sensor — a row of garden path lights, for example — an inline photocell wired into the circuit at the distribution board is the correct approach.
What Your Electrician Will Do: 5 Steps
- 1
Isolate the circuit at the consumer unit
Before touching any wiring, the electrician switches off the relevant MCB (miniature circuit breaker) in the distribution board and verifies with a voltage tester that all conductors in the fitting are dead. In Greece, outdoor circuits are typically 230 V AC; skipping this step is how serious accidents happen, which is exactly why the law reserves this work for licensed professionals.
- 2
Remove the existing fitting or identify the wiring point
For a replacement photocell on an existing fixture, the electrician unmounts the lantern or floodlight from its backplate and notes which wires are present: live (brown or black in older Greek installations), neutral (blue), and earth (green-yellow). On older properties — particularly island villas built before 2000 — wiring colours may not follow current CENELEC standards, so the professional will always test before connecting.
- 3
Connect the photocell wires in the correct sequence
A standard three-wire inline photocell has three connections: the supply live in, the switched live out (to the lamp), and a shared neutral. The electrician connects the sensor's input live to the incoming phase, the output live to the lamp terminal, and the neutral to the neutral bus. On a twist-lock sensor, the wiring is already enclosed in the socket body — the electrician simply installs the socket and plugs in the sensor head.
- 4
Position the sensor head away from the light source
The sensor dome must face open sky — ideally north-facing in Greece so it is not pointing into strong direct sunlight at any time of year. It should never be aimed at the lamp it controls: if the photocell 'sees' the lamp's own light, it detects artificial brightness and switches off immediately, causing a rapid on-off cycling fault. The electrician will angle or shade the sensor head as needed.
- 5
Restore power and test the response
With the circuit live again, the electrician briefly covers the sensor dome with a dark cloth or electrical tape. Within a few seconds the controlled lamp should turn on. Removing the cover should extinguish it within 30-60 seconds (most sensors have a small delay to avoid false triggering from headlights or clouds). If the lamp cycles rapidly or fails to respond, the sensor is wired incorrectly or faulty and must be diagnosed before leaving the site.
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FAQ
- Can I install a photocell myself in Greece?
- For any work that involves opening a junction box or connecting wires at mains voltage (230 V), Greek electrical regulations (PD 108/2013) require a licensed electrician. The one exception is swapping a twist-lock sensor that simply plugs into an existing socket on a compatible fitting — this is mechanically the same as changing a lamp. Even then, if you are unsure, hiring a professional is always the safer choice. All mains electrical work must be covered by a Υπεύθυνη Δήλωση Εγκαταστάτη (electrical installer declaration).
- My outdoor light is cycling on and off rapidly — what is wrong?
- This almost always means the photocell sensor is detecting the light it is supposed to control. Either the sensor is positioned too close to the bulb, or it is angled downward toward a reflective surface that bounces light back at it. The fix is to reposition or shade the sensor dome so it only detects ambient daylight. Occasionally a faulty or undersized sensor for the wattage load causes the same symptom, so the sensor itself may need replacing.
- Do I need a separate photocell for LED lights?
- Most modern photocells are compatible with LED lamps, but always check the minimum load rating on the sensor's data sheet. Older triac-based photocells designed for incandescent loads can flicker or fail to switch correctly with very low-wattage LEDs. Look for a sensor labelled as compatible with LED, CFL, and inductive loads, or ask your electrician to specify a relay-output sensor which works reliably across all load types.