Well, I have three relay boards with 4 relay in each board.
These relays are used to power on the pump, the electrovalves and also some other things like lights.
Everyday, at 4 pm, the power supply for the pump and this things changes from one floor to another, because I share the costs with my neighbour. One relay of the board, conmute a contactor which is the used to change the power supply, from one house or other. The power supply for the arduino is always the same and is always connected.
The other relays are conmuted during the day for power on the pump, the lights as I told you before.
Do you think the problems with the system are in the power supply or is more focused in the I2C bus?
Thank's!