I am looking for advice on how to properly setup a 3-phase to 1-phase switch and with which hardware could this be done. The reason behind is that I have a car charger that can either be operated in 1-phase or 3-phase and I want to be able to charger my car at lower power. Typically, the industry recommends charging at minimum 5A. This means that if you want to charge your car on solar only, with a 3-phase charger you will be charging at 3450W. That’s a lot. To charge at a smaller rate, one need to switch to 1-phase, and then your minimum will be at 1150 W on a 230v. circuit. So the blueprint I will create will put the charger in 1-phase for power surplus between 1150W and 3450W and then switch to 3-phase if above. My charger needs to be properly switched off and switched on again on 1 single phase and to move back to 3 phase it needs to be switched and on again on the 3 phases.
First question: is such a setup allowed according to standards (looking at swiss or german regulations here))
Second question: any such smart switch exists to perform this with Home Assistant? I could have 3 shelly 16A switch next to each other, but looking at alternatives or something more reliable or with this feature built in?
Here is what I want to achieve, but I would need the main MCB to be triggered by Homeassistant:
No, the load is 16A on 3 phases each maximum.
the reason for this setup is that I need to steer phase L1 and phase L2-L3 separately. When running on 3 phases, you run at 400volts 16A 3-phase current, when running L1 only, you are at 230v 16A 1-phase current.
I’m not sure the Pro 3 has everything required to run such a switch, hence my discussion topic. Playing with 3-phase current requires double attention and the shelly 3Pro is rated 230v and not 400v, so i doubt it’s possible.
To my understanding, the contactor gives you first the ability to not directly switch the load (safer?), enables higher load than the switch itself (would be a must if i would be running a 22kw charger on a 32A circuit) and enables “mechanical” simultaneous switch of 2 phases or 3 phases with a single phase switch.
Auxiliary contact 13-14 confirms C1 is actually closed
Feedback goes to SW1 input on Shelly Pro 2PM
Contactor 2 → Shelly Channel 2 (SW2):
Auxiliary contact 13-14 confirms C2 is actually closed
Feedback goes to SW2 input on Shelly Pro 2PM
Why Both Feedbacks Are Important:
State Verification: Home Assistant knows the actual contactor states, not just what was commanded
Fault Detection: If a contactor fails to close/open, the Shelly detects it immediately
Safety Interlock: You can program logic to prevent switching if contactors don’t respond correctly
Monitoring: Track contactor operations and detect wear/failure before it becomes critical
Now both contactors have proper feedback loops to the Shelly Pro 2PM, giving you complete monitoring and control! The schematic is functionally complete and ready for your electrician.
At 16A, in 3-phases at 400v, you obtain 11kW. At 5A, in 3-phases at 400v, you are at around 3.45kW.
This particular charger enables setting the amperage over Modbus.
