I have two Fibaro FGS-222 double relays. The are both used as potential free relays. One only has the primary relays connected (second channel is not used). The other did too, but today I connected the second channel of that 222.
Now, when I use the Homey App to switch that second channel ON, it switches ON and immediately switches OFF again. I thought it must have automatic switching of (with a short delay) set to ON. But that value is 0.
I checked the other settings and compared them with the other 222 (of which I can switch ON / OFF the relay’s second channel). All settings are the same.
That’s how I have connected it. But the second relay switches off immediatelly after manually using the App to switch it on. Relay 1 switches a central heater (cv-ketel) ON/OFF. Relay 2 is now connected to a potential free input on a water heater system.
What do you mean by “connected between IN and Q2”? You shouldn’t connect anything between them… The load should be connected between Q2 and neutral wire.
Do you have three phase electric system in your house? If the central heater control voltage is from different phase than water heater system it will make a short circuit between phases because the FGS222 uses one common (IN) for both channels as stated before by Caseda. That could also break the FGS.
What about the loading of the output Q2? Was it over 1,5kW per channel?