Dimmable and smart downlights that dim all the way down without the flicker

A halogen lamp is a simple resistive load and it will dim on almost anything. An LED downlight is a small electronic driver feeding a light engine, and the driver has opinions about how the power arrives. Put a modern LED on a dimmer built for halogens and the driver is fed a chopped waveform it was never designed for. The result is the list above: flicker at the low end, an audible buzz, a fitting that will not go below half, or one that never quite switches off.

The usual culprit is a leading-edge dimmer, the type fitted in many Melbourne homes from the 1990s to the mid-2010s. It cuts the front of each mains cycle, which suits a halogen filament and upsets an LED driver. A trailing-edge dimmer cuts the back of the cycle instead, which LED drivers handle smoothly.

Three other causes turn up regularly. Fittings that were never dimmable in the first place, sold as LEDs and simply wired to the old dimmer. A retrofit LED lamp pushed into a 12 volt halogen holder, where the old transformer and the dimmer fight each other. And a mixed ceiling: one replacement fitting from a different maker, dimming on a different curve to its neighbours, so the row never looks even. Each has its own fix, and the first job on any dimming call is working out which one you have.

Dimming LEDs well is a matching exercise, not a matter of buying a dearer switch. The electrician checks four things before a dimmer goes on the wall.

The fittings are dimmable. It is printed on the fitting. If they are not, no dimmer will make them dim, and the honest answer is to replace them with dimmable IC-4 LEDs, which we do in the same visit.

The dimmer is a trailing-edge type rated for LED loads. Every LED dimmer has a minimum and maximum load. A single 9 watt fitting on a dimmer that wants more than that will misbehave just as badly as too many fittings will.

One dimmer, one set of matched fittings. A dimmer controls a circuit, so all the fittings on it should be the same model, the same wattage and the same colour setting. When a room has one odd fitting, we replace it rather than tune around it.

Tested at the bottom of the range. A dimmer that is smooth at 80 percent tells you nothing. The electrician runs each circuit down to its minimum, listens for buzz at the wall and at the ceiling, checks for glow with the switch off, and adjusts the dimmer’s minimum level so the low end is steady.

Where the wiring allows, we can also fit a dimmer on a two-way circuit so the lounge dims from either door, and we replace old halogen dimmers that were left in place when the fittings were changed by someone else.

Tri-colour fittings. Many integrated LEDs now carry a small switch on the body that selects warm, neutral or cool white, roughly 3000K, 4000K and 5000K. We set it at install, to the same setting on every fitting in the room, and note it on the job so a future replacement matches. It is a five-second change if you want a different white later, but it is a change in the roof, not on an app.

Smart control comes in two forms and they are not the same. A smart dimmer switch replaces the wall switch, dims an ordinary set of dimmable downlights, and connects to your home Wi-Fi. The lights still work from the wall like normal lights, which matters for guests and for the day the internet goes down. A smart fitting puts the radio in each downlight; it can change colour temperature from the app and works with Google Home, Amazon Alexa or Apple Home depending on the product, but the wall switch has to stay on for it to respond, which is the thing that frustrates most owners.

Scenes. Either form lets you save a setting: a low warm glow for a film, full neutral light for cleaning, a hallway that comes on dim after midnight. Voice control runs through whichever assistant you already use. We set the first scenes up with you on the day.

Our advice is usually a smart dimmer switch on ordinary dimmable IC-4 fittings. A failed fitting is a plain like-for-like swap, and the room never depends on an app to turn the lights on.

Dimming and smart control are easy to oversell. Here is how we call it for a typical Melbourne home.

Worth dimming: the living room and any room with a television, the dining room, the main bedroom, and the bathroom for a low light at night. These are the rooms where you want two or three levels of light in a day, and where a trailing-edge dimmer changes how the room feels.

Worth making smart: the same living areas if you already use a voice assistant or want scenes, the front hallway or porch for a timed light when you are away, and a kids’ bedroom where a slow fade at bedtime is useful. A smart dimmer switch covers all of these.

Not worth it: the laundry, the garage, the walk-in robe, the toilet, and most hallways. These rooms want full light for a short time. A good IC-4 fitting on a plain switch does the job, and we will say so when you ask.

The kitchen is the one to think about. Dimmable task lighting over the benches is useful when the kitchen opens onto the living area; smart control matters less because the light is either on for cooking or off. A trailing-edge dimmer on the bench run and a plain switch on the pantry is the usual answer.

Whatever the rooms, the fittings underneath are the same ones we fit everywhere: integrated IC-4 LEDs the insulation can cover, so a dimming upgrade never gets in the way of an insulation job later.