I understand that it is the type of RCD that needs to be reset if the power fails, I believe this may be a safety feature for power tools, so they will not restart if the power if restored. I am not sure they are suitable for a boat, I found it annoying that I would lose all power if the mains was momentarily disconnected. So I have replaced mine about 10 years ago with a normal RCD, which does not trip in the same way. Hope that helps.
regards
Angus
The membership association for owners of Dufour Yachts