Just to expand on the grounded neutral, it is optional in the code that if you have a isolated control transformer, that it sounds like you have, it is optional whether you setup a grounded neutral, IOW re-reference the secondary to ground.
When choosing which conductor you ground is purely optional as at that point they are totally identical.
The conductor chosen to be earth grounded should be done right at the transformer and no where else.
This terminal will be secured to chassis and a ground wire and a neutral conductor will be taken from this point and be the ONLY place where the neutral and ground conductor connection is made.
As to using it without grounded neutral it is possible but there should be fusing in both secondary conductors as opposed to just one with grounded neutral.
But if you are using the 100 and 120v tap then the '0' conductor would be the one to ground in that case.
BTW, all ground and machine bonding conductors together with shields should go to a central ground 'star' point where the service ground should also be terminated.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.