Do I need a Shelly Bypass?
The Shelly Bypass is specifically designed for using a Shelly 1L and Shelly Dimmer 2 on a lighting circuit to control lights. The Shelly 1L is a standard smart lighting relay, whereas the Shelly Dimmer 2 is a smart lighting relay with dimming capabilities.
Any smart light switch needs to draw enough current and power to operate at all times; Shelly’s are no different. Most smart light switches on the market require permanent live and neutral feed to the light switch to provide the smart switch with power even when the light is off.
However, the Shelly 1L and Shelly Dimmer 2 can operate without a neutral feed. If you’re not sure if you have neutral wiring, check out our guide on How To Install A Shelly Without Neutral Wiring.
A Shelly Bypass is needed when the load being controlled by the Shelly is less than 10 or 20 Watts:
- Shelly 1L requires a bypass if the load is less than 20W
- Shelly Dimmer 2 requires a bypass if the load is less than 10W
Regardless of whether you are using a Shelly 1L or Shelly Dimmer 2, the Shelly Bypass is connected in parallel with the load:
Shelly 1L Wiring with Bypass
This is the full wiring diagram for the Shelly 1L:
- L will need to be wired to your permanent live Feed In.
- O will be wired to your Switched Live feed.
- The Shelly 1L has two inputs (SW1 and SW2) which can be used to toggle the light. Your light switch should be wired to SW1 and Sx so that when the switch is closed a circuit will be completed between Sx and SW1.
Shelly Dimmer 2 Wiring with Bypass
This is the full wiring diagram for the Shelly Dimmer 2:
- One of the L terminals will need to be wired to your permanent live Feed In.
- O will be wired to your Switched Live feed.
- The Shelly Dimmer 2 has two inputs (SW1 and SW2) which can be used to toggle the light and/or increase and decrease the brightness. Your light switch should be wired to SW1 and one of the L terminals so that when the switch is closed a circuit will be completed between L and SW1.
Conclusion
The Shelly Bypass is needed when you are using a Shelly 1L and Shelly Dimmer 2 without neutral wiring where the load is less than 10/20W:
- Shelly 1L requires a bypass if the load is less than 20W
- Shelly Dimmer 2 requires a bypass if the load is less than 10W
If you have neutral wiring you do not need a Shelly Bypass, regardless of the load.