Schneider Altivar 320 wiring / setup help needed

[Neale]

I think that I might have found the problem. Altivar installation manual, top of p48. "If using Sink Int do not connect 0V to ground". The manual is not consistent but I think that they use "0V" and "COM" for the same connection. Unfortunately, the HDDB2 has one side of its output connected to ground, so that this connection breaks the Altivar connection rules.

I think that the easiest and safest way to connect the two devices is to use an external relay between the BOB and the VFD. You can then use the Source mode on the VFD, which allows you to connect the analogue ground on the BOB to COM on the VFD (as far as I can see - but I have not read the whole manual!). If you use 12V relays, then you already have 12V available from the BOB. Connect relay coil between 12V and BOB output pin, and connect the relay NO contacts in place of the switches shown in VFD installation manual p48, first diagram. This is an example of the kind of relay that you could use although I do not know what is easily available in your country.