Smart lighting is one of the most satisfying and impactful upgrades you can make to your home, especially when paired with Home Assistant for powerful automations and Shelly devices for local-first control. But as with any smart tech rollout, a few technical details and quirks can surface along the way.
In this post, we cover a real customer case exploring how the Shelly Dimmer Gen 3 behaves when paired with third-party wall switches — and we dive into two additional known issues you might run into with the Dimmer Gen 3, plus how to fix or avoid them.
Customer Q&A: Using Shelly Dimmer Gen 3 With Home Assistant and a Wall Switch
A customer is in the process of converting their entire home lighting system to Shelly + Home Assistant and asked three great technical questions about how the Shelly Dimmer Gen 3 integrates with a wall switch and continues to function during network outages.
Q1: Can I use a 3rd-party push-button wall switch to control on/off and dimming?
✅ Yes!
The Shelly Dimmer Gen 3 fully supports momentary push-button switches connected to its S1/S2 terminals. Here's how it works out of the box:
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Short press: Toggles the light on or off.
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Press and hold: Gradually dims the lights up or down.
This gives you tactile control at the wall without losing smart automation via Home Assistant.
Q2: If Home Assistant or my Wi-Fi network goes down, will it still work?
✅ Yes!
The beauty of Shelly devices is that they are designed to work locally. Even if your Wi-Fi or Home Assistant server is down, the Dimmer Gen 3 still works at the wall switch — on/off and dimming are preserved because the logic is onboard.
This ensures your lights continue to function like a traditional dimmer, even in offline scenarios.
Q3: Are there any special requirements for the wall switch?
✅ Yes – it must be a momentary (push button) switch.
Unlike standard toggle switches, momentary switches return to their original position after you press them — like a doorbell. This is essential for the Shelly Dimmer to distinguish between a tap and a hold, allowing smooth dimming control.
Q4: Dimmer Keeps Rebooting or Overheating
Symptoms:
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Dimmer disconnects from Wi-Fi after a few minutes
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Device restarts unexpectedly
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Light flickers or behaves erratically
Cause:
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The load is too low, or LED drivers are incompatible with trailing-edge dimming.
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The dimmer is overheating in a confined switch box without ventilation.
Fix:
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Ensure your lighting load is within the required 10W–200W range and dimmable.
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If the load is low (e.g., only one small LED downlight), use the Shelly Bypass accessory.
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Allow airflow to the Shelly device or mount externally using DIN rail options where appropriate.
Q5: Wall Switch Doesn’t Dim — Only On/Off
Symptoms:
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Short presses toggle the light
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Holding the button does nothing
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Dimming only works via app or Home Assistant
Cause:
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The wall switch may be a latching (toggle) switch rather than a momentary switch.
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Incorrect settings in the Shelly web interface or Home Assistant configuration.
Fix:
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Replace the switch with a momentary push-button model.
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In the Shelly app or web UI, check your “Input Type” settings for S1/S2 — it should be set to momentary or edge mode as needed.
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Restart the dimmer and re-test after saving settings.
Pro Tip: Planning a Reliable Smart Lighting Retrofit
If you're heading into a full home retrofit, here are our top recommendations for a reliable, future-proof setup:
✅ Use Shelly Dimmer Gen 3 for every dimmable circuit
✅ Use momentary push-button switches throughout
✅ Configure each dimmer for local-first operation (disable Shelly Cloud if desired)
✅ Use Home Assistant + MQTT or CoAP integration for fast local updates
✅ Plan for ventilation in tight switch boxes — or consider DIN rail Shelly Pro devices for centralised setups
By starting with the right devices and ensuring your wiring, switches, and settings are compatible, you can achieve an offline-capable, user-friendly lighting system** that works beautifully with Home Assistant and looks and feels just like traditional lighting — only smarter.