Shelly Bypass

If you are using the Shelly 1L or the Shelly Dimmer 2 in a place with no neutral wire (such as behind a light switch) and you live in the UK, yes you most likely do.

If you are installing a Shelly Bypass in a lighting circuit in the UK, you will need to attach the Shelly Bypass between the Output wire going to the lightbulb and the neutral going to the other side of the lightbulb. It will feel very unnatural to connect the wire this way. Most people in the UK have a ceiling rose or light fitting which allows the space for a Shelly Bypass. They are really small, being only 39 mm x 23 mm x 7 mm.

A Shelly Bypass is required where there is neutral wire and where the power consumption is less than 20 watts. If the load of the light is very low (typically, LED lights), you need to add some form of load, that's where the need of a bypass comes in!

Rather than turning off the light, the Shelly 1L and Shelly Dimmer 2, dim the light so low, it stops glowing, leaving a very small current flowing through the circuit of the Shelly Device to keep it running, even when the light is off.

No, you only need a Shelly Bypass where there is no Neutral wire.

If you have a Neutral wire you may wish to consider either the Shelly 1 or the Shelly 1PM unless you need the dimming function specifically.