The art of the home
LED ceiling light flickering: the three causes, in order
Published on ·3 min read
A flickering LED is more than a visual nuisance: fast flicker, even barely perceptible, tires the eyes and triggers headaches in some people. Before replacing the luminaire, it is worth finding where the problem comes from, because in most cases the luminaire is not at fault.
Three causes cover nearly every situation, and they are told apart by the type of flicker.
Cause number one: the wall dimmer
Dimmers installed before LEDs became standard were designed for incandescent bulbs. They work by chopping the mains voltage, and require a minimum load often around 40 W. A 10 W LED never reaches it, which makes the circuit oscillate and produces the flicker.
The symptom is recognisable: the luminaire flickers mainly at low settings and steadies at full power. The remedy is to replace the dimmer with a model explicitly marked LED-compatible, with a minimum load of a few watts.
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Cause number two: the luminaire driver
Fast flicker, permanently present and independent of the setting, comes from the power unit built into the luminaire, called the driver. A cheap driver lets residual ripple through, and the LED follows that ripple a hundred times a second.
The eye does not always consciously see it, but a phone camera reveals it: film the luminaire while lit, and scrolling bands appear on screen. That is a design fault, and the only answer is to change the luminaire.
- ·Flickers at low setting, steady at full: incompatible dimmer
- ·Permanent shimmer, bands visible on camera: poor-quality driver
- ·Flickers in bursts, several rooms affected: connection or neutral to check
- ·Flickers at start-up then steadies: normal behaviour of some drivers
Cause number three: the installation
Irregular flickering, affecting several luminaires or coinciding with a large appliance starting up, comes from neither the dimmer nor the driver. It points to a loose connection, a weakening shared neutral, or an undersized cable.
It is the only one of the three that calls for an electrician, and the only one not to put off: a connection heating up in a ceiling box is the start of an incident, not an inconvenience.
Start with the dimmer, the culprit in the vast majority of cases, and the check is free: take it out of the circuit or test the luminaire on a plain switch. If the shimmer persists, film the light with your phone. And if several rooms are affected, stop diagnosing and call a professional.
Frequently asked questions
Why does my LED flicker with a dimmer?+
Because the dimmer needs a minimum load, often 40 W, which a 10 W LED never reaches. The circuit oscillates and the light follows. You need a dimmer explicitly marked LED-compatible.
How do you know if a luminaire really flickers?+
Film it lit with a phone camera. If dark bands scroll across the screen, the current ripples and the LED follows. The eye does not always catch it, the sensor does.
Is flicker dangerous?+
Not electrically, but fast flicker tires the eyes and triggers headaches in some people. That is reason enough to replace a luminaire that produces it permanently.
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