You install a Shelly 1L Gen3 behind the switch, everything seems fine, and when you turn the light off the bulb keeps a faint glow. Or worse: it flickers every few seconds.
You haven't done anything wrong. It's a predictable consequence of how neutral-less devices work with modern LED bulbs, and it has a specific solution.
Why it happens
A Shelly needs current to stay alive: to keep the Wi-Fi, the processor and the relay running. Models with neutral take it from there. Neutral-less models don't have that option, so they take it from the only place available: through the load itself.
With a 60 W incandescent bulb, that minimal current was irrelevant: the filament didn't even notice. A 7 W LED is another story. Its electronics need very little energy to light up, and that residual current is enough to light it dimly or to charge its internal capacitor until it flashes, discharges and starts again. Hence the rhythmic flicker.
The threshold: 20 watts
Shelly documents it with a clear figure: on devices that work without a neutral wire, loads below 20 W need a bypass.
Do the math for your light point. Three 5 W LEDs add up to 15 W and are below the threshold. Six 5 W LEDs add up to 30 W and probably won't cause trouble.
The four symptoms
- Glow with the light off. The most common and most recognizable case.
- Rhythmic flicker. Flashes every few seconds, both off and on.
- The Shelly drops off Wi-Fi when you switch off. It doesn't get the minimum current and loses power.
- The lamp doesn't fully light up. It stays at half light or doesn't respond.
The solution: the bypass
The bypass connects in parallel with the load and offers an alternative path for that current. The Shelly still powers itself the same way, but the current no longer passes through the bulb, so the bulb switches off completely.
It draws less than 4 W and measures 39 × 23 × 13 mm, small enough to fit inside most light fixtures.
Which one you need depends on your device: the Bypass for 1L/2L Gen3 or the Bypass for Dimmer Gen3. We detail it in the guide to choosing a bypass.
Before buying, rule this out
The bypass solves a very specific problem. Check first that it's yours:
- Does your Shelly work without neutral? If it's a 1PM, a 1 Gen4 or any model connected to neutral, the bypass isn't the solution.
- Is the load below 20 W? If you have 40 W of LED and it still flickers, the cause is something else.
- Have you tried another bulb? Some very cheap LEDs flicker because of their own driver.
- Is the symptom a Shelly reset when switching off? That points to an inductive load, and then what you need is an RC Snubber, not a bypass.
Frequently asked questions
Can I put a more powerful bulb instead of the bypass?
It works, but it's a worse solution: you permanently use more electricity to avoid a one-off accessory. And the bypass itself draws less than 4 W.
How many bypasses do I need if I have several light points?
One per controlled circuit, not per bulb. If a Shelly 2L Gen3 controls two different circuits and both are below 20 W, you'll need two.
Does it get hot?
It dissipates some heat, like any component that consumes energy. Its working range goes up to 70 °C, but it's best not to enclose it in a sealed space with no ventilation.
Does it need to be set up in the app?
No. It's a passive component: you connect it and it works.
Can I install it myself?
It involves working on the fixture's electrical installation. Cut the supply at the panel and verify the absence of voltage before touching anything. If you don't feel confident, use an installer.
Related guides
- How to install the Shelly Bypass step by step
- Snubber or bypass: which one you need
- Which bypass is for you
Not sure whether your case fits? Write to us with the Shelly model, the power of your bulbs and whether your installation has neutral. Technical support in English.
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