Short answer
An old dimmer can have a minimum load of as much as forty watts. Four LED bulbs together do not reach that, and then the dimmer starts to behave erratically: flickering, buzzing or not switching fully off. An LED dimmer with a low minimum load solves that. Choose dimmable bulbs from one brand and do not mix them.
Who this article is for Anyone with LED lighting that misbehaves. Replacing a dimmer is work behind a switch and therefore for the installer.
Why it goes wrong
An incandescent bulb drew 40 to 60 watts. Dimmers were made for that: below a certain load they do not work stably. A 6 watt LED bulb is far below that minimum, and six of them together often still do not reach it.
What you then see:
- flickering at low level
- buzzing in the dimmer or in the bulb
- ghosting: the bulb keeps glowing faintly while it is switched off
- part of the dial range where nothing happens
What you need
An LED dimmer with a low minimum load, usually from 1 to 3 watts. Also pay attention to the type:
If you do not know for your bulbs, choose universal.
| Type | What for |
|---|---|
| Leading edge | old transformers, some halogen |
| Trailing edge | most LED drivers and electronic transformers |
| Universal | adapts itself, the safest choice with unknown bulbs |
If your bulb or driver states which dimming method it needs, follow that. If it says nothing, choose universal.
Do not mix brands
LED bulbs respond differently to the same dimming signal. Four bulbs from three brands on one dimmer give four different brightness levels. Buy them all at once, of the same type, and keep a spare.
If the ghosting persists
Sometimes a bulb keeps glowing faintly because of leakage current in the wiring, especially with a long cable run or a switch with an indicator light. A suppression capacitor across the lamp solves that. It is a small part that goes in the light fitting or in the box.
Better than dimming: splitting
For most rooms it works better to switch lights in groups than to dim everything. Two switches, one for the spotlights above the worktop and one for the rest, give you more in practice than a dimmer you never quite set right.
During a renovation that only costs an extra cable. What to include now is explained in when the electrician comes.
From my own work
In a home in Elsloo six LED spotlights had been fitted on the dimmer that had been there for twenty years. They flickered at low level and kept glowing faintly when switched off. An LED dimmer in, and it was over. There was nothing wrong with the bulbs, though the customer had already had them replaced twice.
When to call an electrician
- The bulbs flicker or keep glowing while switched off
- The dimmer gets warm or buzzes audibly
- You want to dim several groups of lights separately
Swapping a dimmer is a short job that I usually combine with other work. Call +31 43 204 18 26 or request a quote.
Frequently asked questions
Why does my LED flicker on the dimmer?
Almost always because the dimmer was made for incandescent bulbs and has a minimum load that you do not reach with LED.
My bulb keeps glowing faintly while switched off, how is that possible?
Leakage current in the wiring, often with a long cable run or a switch with an indicator light. A suppression capacitor solves it.
Can I put different brands of LED bulbs on one dimmer?
Better not. They respond differently, so you end up with four different brightness levels.
Further reading
Installing outdoor lighting: what goes on underground
The light is the fun part, the cable the most important. Lay an empty duct now and you can extend later without digging.
The light is not working: check it yourself in four steps
Nine times out of ten it is the bulb, the lampholder or the switch. The tenth time it is a connection, and then you call.
Smart lighting without the hassle: what works and what to avoid
Smart bulbs are fun until someone presses the ordinary switch. Smart switches are more boring and work better.
Questions and comments
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