Why do my new LED strips hum on the dimmer in my Kerrisdale kitchen?

LED strip humming on a dimmer is almost always a compatibility mismatch between the dimmer's control method and the LED driver, and it is one of the easier electrical annoyances to fix without calling anyone.

What is actually causing the hum

Most dimmers sold before 2018 or so use a technique called phase-cutting: they chop the AC sine wave to reduce average voltage. Incandescent bulbs tolerated this without complaint because a hot filament smooths out the flicker. LED drivers, especially the cheap constant-voltage drivers bundled with strip kits, react to that chopped waveform by vibrating at the switching frequency, typically 120 Hz, which lands squarely in the range human ears find irritating. The strip itself can also vibrate if it is mounted loosely against a surface that acts as a sounding board, like an MDF cabinet face.

A few things make it worse. Older Kerrisdale homes often have 15A lighting circuits that were wired for incandescent loads, so the dimmer may be a legacy leading-edge (triac) model that was never designed for LEDs. Running the dimmer near the bottom of its range amplifies the effect because the phase-cut angle is at its most aggressive. A very short strip, or a strip whose total wattage is well below the dimmer's minimum rated load, causes the same problem.

The fix is almost always a new dimmer rated specifically for LED loads, ideally one that lists your strip's driver brand in its compatibility table. Trailing-edge (ELV) dimmers are generally quieter with LED drivers than leading-edge models. Lutron and Leviton both publish compatibility lists, though I am not recommending a specific brand here, just the category. Budget $30 to $80 for a quality LED-rated dimmer at a local electrical supply house.

A few other things to check before you buy anything. Make sure the strip is physically secured flat against its mounting channel or aluminium extrusion, because an air gap lets it rattle. If the driver is a separate brick-style unit sitting in a cabinet, isolate it from the shelf with a piece of foam or rubber, since the driver casing itself can be the noise source. Also confirm the strip's total wattage is within the dimmer's rated range, not just under the maximum but also above the minimum load, which is often printed on the dimmer's label.

Swapping a dimmer is work a homeowner can do on a de-energised circuit: turn off the breaker, confirm the circuit is dead with a non-contact tester, swap the device, restore power. No permit is required for a like-for-like device replacement in BC. If the wiring in the box is aluminum (common in Kerrisdale homes built in the 1960s and early 1970s), do not proceed on your own; aluminum wiring needs CO/ALR-rated devices and proper pigtailing by a licensed electrician.

If a new LED-compatible dimmer does not solve it, the strip driver itself may simply not be dimmable, or the strip wattage may be too low for any phase-cut dimmer to handle cleanly. In that case a PWM (pulse-width modulation) controller on the DC side of the driver is the cleaner solution, though that changes the wiring arrangement and is worth a quick conversation with an electrician.

If you want a licensed electrician to assess the circuit and swap the dimmer properly, Vancouver Electrical Repair can match you with a local one for free.