Growatt SPH switch function?

Hi all, I’m having problems controlling my Growatt SPH + Battery system via both Home Assistant and Solar Assistant.

  1. Can anyone tell me what the switch to the right of the Growatt SPH title is/does in the attached picture.
  2. Should I have Backup EPS enabled as show in the picture? I don’t have any backup system and I’d hate to fry an engineer if there was a power outage (we do get the odd short one).