Switching high voltage applications on different electricity supplies

Hardware
1

Hi all,

I need some advice.

We live largely off grid, using a Victron inverter. We still have a connection to the grid, but we only flip that breaker up during long periods of wet weather when the solar hasn't charged enough, or on the odd occasion when we've run out of solar-heated water.

From within the inverter system, I need to switch an electric geyser that lives outside the system, connected to grid power. To switch any high voltage applications I would normally use a small opto-isolated relay to switch a huge contactor that can handle big amps.

However, I find myself wondering whether there would be any risk or consequence to the microcontroller (ESP32) living inside the inverter supply, switching a device powered from the grid. Is there a risk of the two isolated electric supply systems coming into contact with each other?

I would rather understand and pre-empt such a problem, rather than discover it during deployment. Currently the only thing I can think to do is to have the microcontroller (ESP32) live on the utility side, but supply is shitty, and I've lost a Sonoff or two that way. I would prefer that not happen anymore.

Please offer opinions. I mostly want to understand, even though I might not actually implement this.

Thank you.

2

The risk of the contactor coil supply coming in contact with the grid supply is minimal, if using contactors built to the correct standards and the minimal risk should be negated with the correct fusing wiring and insulation. Contact an electrician for this info

P.s. any thing under 1000v AC is considered low voltage

2 Likes
3

Hi @E1cid, thank you for responding.

I have several automation jobs that physically intersect near the distribution board, so simply adding a relay to the existing setup seems appealing. Your advice about fusing etc is exactly the sort of wisdom I was after.

Thank you also for the correction/perspective about voltage. In my world, 220V is plenty stressful as is.