Overview
Shelly Wave devices such as Shelly Wave 1, Shelly Wave 1 Mini, Shelly Wave Pro 1, Shelly Wave Pro 2, and Shelly Wave Pro 3 use dry contact relay outputs.
A dry contact relay output does not send voltage by itself.
The relay works like a controlled switch. When the relay is turned on, it connects the relay input terminal to the relay output terminal.
This means the output terminal will only have voltage if voltage is also supplied to the related input terminal.
Supported devices
This logic is valid for the following devices:
| Device | Relay output type |
|---|---|
| Shelly Wave 1 | Dry contact relay |
| Shelly Wave 1 Mini | Dry contact relay |
| Shelly Wave Pro 1 | Dry contact relay |
| Shelly Wave Pro 2 | Dry contact relay with multiple inputs and outputs |
| Shelly Wave Pro 3 | Dry contact relay with multiple inputs and outputs |
Important terminals
For Shelly Wave 1, Shelly Wave 1 Mini, and Shelly Wave Pro 1, the main relay terminals are usually:
| Terminal | Function |
|---|---|
| L | Device power supply |
| N | Neutral |
| I | Relay input |
| O | Relay output |
| SW | Switch input |
For Shelly Wave Pro 2 and Shelly Wave Pro 3, the same rule is valid, but the devices have more than one relay channel because of that have multiple inputs (I) and outputs(O) and switches (SW)
This means they have multiple relay inputs and outputs. Examples:
| Device | Relay channels |
|---|---|
| Shelly Wave Pro 2 | 2 relay inputs, 2 relay outputs and 2 switches connections |
| Shelly Wave Pro 3 | 3 relay inputs, 3 relay outputs and 2 switches connections |
Each relay input works together with its related relay output.
For example:
Input I1 works with output O1
Input I2 works with output O2
Input I3 works with output O3, if available
How the dry contact relay works
The relay inside the Shelly Wave device does not create voltage on the output.
When the relay is off:
The relay input and relay output are not connected.
No voltage is passed to the load through the output terminal.
When the relay is on:
The relay input is connected internally to the related relay output.
Any voltage connected to the relay input is passed to the relay output.
The connected load can then receive power.
Why the output may not have voltage
A common mistake is to expect the output terminal to provide voltage automatically.
This is not how dry contact relays work.
The output terminal is only a relay contact. It does not provide voltage unless the related input terminal is connected to a voltage source.
For example, terminal O will not output 230 V AC unless terminal I is also supplied with 230 V AC.
On devices with multiple outputs, the same rule applies to each channel.
Examples:
O1 will only receive voltage from I1
O2 will only receive voltage from I2
O3 will only receive voltage from I3, if available
Example: Using 230 V AC on the output
If you want to have 230 V AC on the output, you must connect the phase wire L to the related relay input.
For a single-channel device:
Connect phase L to terminal I
The load is connected to terminal O
When the relay closes:
Terminal I is connected internally to terminal O.
The 230 V AC from terminal I is passed to terminal O.
The connected load receives power.
For multi-channel devices:
Connect phase L to I1 if you want 230 V AC on O1
Connect phase L to I2 if you want 230 V AC on O2
Connect phase L to I3 if you want 230 V AC on O3, if available
Correct wiring logic
To switch a 230 V AC load with a single-channel Shelly Wave device:
Connect L and N to power the device.
Connect the phase wire L also to terminal I.
Connect the load input to terminal O.
Connect the other side of the load to N.
To switch 230 V AC loads with a multi-channel Shelly Wave device:
Connect L and N to power the device.
Connect the phase wire L to the needed relay input, such as I1, I2, or I3.
Connect the load to the related relay output, such as O1, O2, or O3.
Connect the other side of each load to N.
NOTE: You may find wiring examples on the following link, wiring of the Shelly Wave devices are the same Wi-Fi devices.
Important note
The relay outputs are potential-free. This means the relay contacts are separated from the device power supply.
Because of this, the output will not work as expected if the related relay input is not supplied with the voltage that must be switched.
Always make sure that the correct input is used for the correct output.
Summary
Shelly Wave dry contact relays do not send voltage from the output by default.
They only connect the relay input to the related relay output when the relay is active.
To get voltage on the output, the same voltage must first be connected to the related input.
This rule is valid for:
Shelly Wave 1
Shelly Wave 1 Mini
Shelly Wave Pro 1
Shelly Wave Pro 2
Shelly Wave Pro 3
The only difference is that Shelly Wave Pro 2 and Shelly Wave Pro 3 have multiple relay inputs and outputs. Each input controls its own related output.