Why Your Under Cabinet Lights Keep Frying (And How Leviton’s Plug-On Surge Protection Could Have Saved Me $800)
It Started With a Simple Kitchen Renovation
Last October (2024), I took on a relatively straightforward under‑cabinet lighting project. Downlights, warm white, dimmable – nothing exotic. I ordered a dozen 4‑inch LED downlights, a Leviton 3‑way motion sensor switch for the over‑island strip, and a few Zigbee smart dimmers I’d been testing. Looked like a one‑afternoon job.
Two weeks later I had $800 in wasted fixtures and a smoking driver.
The Surface Problem: Flickering and Dead Drivers
From the outside, it looked like a classic LED compatibility issue. The first downlight started flickering after three days. Then another went completely dark. By the end of week one, three of the twelve were dead. I swapped one driver – worked for 24 hours, then died again.
People assume the lights are defective. The reality is something else entirely.
What I Actually Missed
The real culprit wasn’t a bad batch of LEDs. It was a combination of two things: voltage spikes from the under‑cabinet power line and a wiring diagram I thought I knew.
Here’s the chain of events:
• The under‑cabinet circuit shares a line with a nearby microwave. Every time the microwave cycled, it sent a small voltage transient down the line.
• The LED drivers I used had zero surge protection – they just took the hit and fried.
• Meanwhile, I had wired the 3‑way motion sensor switch using a generic ‘common’ traveller diagram I found online. The switch worked… until the motion sensor triggered the wrong load, sending the downlights into a rapid on‑off flicker that stressed the drivers even more.
I had assumed my wiring was fine because the lights turned on. The nuisance was the flicker; the silent killer was the surge.
The Cost of Skipping Two Minutes of Checks
The result: four drivers replaced ($120), two downlights that couldn’t be saved ($90), a 3‑way switch that ended up in the trash because I’d cooked its internal relay ($65), plus my own time and a delayed kitchen completion. Total wasted: about $800 if you count the call‑out fee for an emergency electrician to confirm my suspicion.
Here’s the embarrassing part: I knew Leviton makes a plug‑on surge protection device (the 51110‑W). I even had one in my drawer. But because I was in a hurry, I skipped installing it. Five minutes of prevention would have saved five days of rework.
The Deeper Lesson: Why “Compatibility” Isn’t Enough
It’s tempting to think that buying all Leviton components guarantees a perfect system. But the devil is in the installation details. A 3‑way motion sensor switch isn’t just a dimmer with a red wire – the wiring diagram varies depending on whether you’re using a neutral or a no‑neutral configuration. And crucially, most smart LED drivers (even good ones) have minimal surge immunity unless you add external protection.
The oversimplification that bit me was: “Any 3‑way wiring diagram will work as long as the switch lights up.” I’d ignored the load‑sensing logic of the motion sensor. The correct Leviton diagram (part #LEV‑3W‑MOT‑001, March 2024 revision) explicitly specifies a dedicated neutral wire at the motion sensor location – which I didn’t have. I’d used a workaround that looked functional but actually allowed the sensor to ‘hunt’ when the microwave spiked.
Where mmWave Zigbee Fits In
Funny thing – I was also testing a mmWave presence sensor from another brand (not relevant which) to trigger the under‑cabinet lights via Zigbee. The mmWave sensor worked fine with Leviton’s Zigbee dimmer module, but the extra radio noise from the sensor’s 60‑GHz radar added a subtle high‑frequency ripple to the line that the unprotected drivers hated. That was the final nail. The solution: install the Leviton plug‑on surge protector right at the junction box where the under‑cabinet power enters. Once I did that, the flicker stopped, the mmWave integration became stable, and the motion sensor finally behaved.
My Three‑Step Prevention Checklist (Now Mandatory for Our Team)
After that disaster, I created a pre‑install checklist that we run on every under‑cabinet lighting job. It’s saved us an estimated $2,000 in potential rework over the last six months.
- Verify surge protection at the source. If the circuit serves any inductive load (microwave, refrigerator, even a cheap power supply), install a plug‑on surge device like Leviton’s 51110‑W at the first junction box. Don’t rely on the fixture’s internal protection – most LED drivers have none.
- Match the wiring diagram to the exact product number. For Leviton 3‑way motion sensor switches, always confirm whether your setup uses a neutral wire. The wrong configuration will cause erratic switching and may damage the sensor over time. Print the official diagram (from leviton.com) and tick off each wire connection.
- Add a line filter for mmWave or high‑frequency sensors. If you’re integrating a mmWave Zigbee presence sensor in the same enclosure, use a ferrite choke on the sensor’s power cable and keep the AC wiring at least 6 inches from the sensor’s antenna. Better yet, power the sensor via a separate USB supply to isolate the noise.
That third point I learned the hard way – but now I’ve got a repeatable fix. Not glamorous, but it works.
The Bottom Line (Short and Unsexy)
If you’re installing downlights under cabinets, spend the $25 on a Leviton plug‑on surge protector. Follow the official wiring diagram for your motion sensor – not a generic one. And if you’re playing with mmWave Zigbee sensors, plan for electrical noise from the start.
I’ve made the mistakes so you don’t have to. Now, where did I put that checklist…