where should I connect ground on dual secondary of transformer

Hello gentlemen,

I am trying to use the transformer with dual secondary voltages which are 120VAC and 220VAC out of the transformer. I am not 100% sure if I am connecting ground wire on the right spot.
Please see the attached picture.
I connected the ground at neutral.
Can somebody tell me if that is right?
And what if I connect the ground to X4 instead of Neutral? What can happen?

http://forums.mikeholt.com/showthread.php?t=158756&highlight=dual+transformer+grounding

The above thread may help you out.
Regards,

For your conventional 240/120 center tapped system, your neutral is your "grounded conductor". And that is where you bond it at the source (Your transformer in this case).

If you were to ground at X4, the transformer itself would not care. But you would have 120VAC potential between your Ground and Neutral, and any devices you connect to that would possibly have some major issues. Not to mention the safety hazards with personnel servicing it in the future and potentials not being what they should.