Quote Originally Posted by EddyCurrent View Post
I would definitely use an interposing relay.
You need to. Or any other kind of 'switch'.
You can't directly connect a breakout board / controller output to vfd FWD / DCOM.
It simply does not work (or will break them) .

Put a single wire link between fwd an dcom and fwd will come on. Break that link and it will go off.
Use the relay to control the make or break link.