Substitute your Finder 27.21 relay with the Shelly 1 WiFi switch

The Shelly 1 is my preferred smart WiFi switch. It is defined by the producers as the smallest, smartest and most powerful WiFi switch.

It can be used for:

• controlling an outlet;
• transforming a switch into a smart one;
• behave as a relay.

The relay option may be the most complex one, but it is probably the most useful one when it comes to controlling lights. In fact, differently from the diverter option, with a single relay it is possible to control one or more lights from multiple buttons.

The wiring documentation on the Shelly website is really good. But if you know nothing, or little, about electrical wiring and want to switch your existing Finder 27.21 relay (the same logic applies for the 27.01 one) with the new Shelly 1, here’s what you should be doing.

The Finder 27.21 relay is characterised by three inputs: 2, A1 and A2. All three of them will need to be moved to the Shelly 1.

The Shelly 1 is characterised by five inputs: O, I, SW and L will be mapped to the Finder inputs while N will provide power to the WiFi switch.

Before starting to move wires around, make sure that electricity is cut out! It is for your own safety in the first place but also for protecting your own home/office electrical system.

If you have any doubts or don’t feel comfortable changing the wiring yourself, please consider confronting with your electrician.

Here’s how to more wires from the Finder relay to the Shelly switch.

• Wire from input 2 of the Finder relay should be connected to Shelly input O.
• Wire from input A1 of the Finder relay should be connected to both Shelly input L and I.
• Wire(s) from input A2 of the Finder relay should be connected to Shelly input SW.
• Finally (there are no more wires to move from the Finder relay), Shelly input N should be connected to a clean + pole (it is usually the blue wire taking electricity to your system).

This is it! It is now possible to power again your system. The Shelly 1 WiFi switch will turn on and it will be ready to be paired with the companion mobile application.

Don’t forget to correctly configure the Shelly 1 settings.

• Power on default mode should be set to Restore Last Mode.
• Button type should be set to Momentary.

It is up to your imagination to decide how to create and combine scenes and automations. Happy hacking! 🤖