Question about grounding a 208Y - 480 Delta Transformer

[hvacsolutions]

So I am a building engineer by trade and have a question on grounding a transformer. On a 208Y Wye to 480 Delta transformer do you have to ground both sides or just one. I see the XO on the 208 side and I noticed that on the Delta side there is what seems to be a leg that goes to the center of the delta. But do I have to ground both sides or just one?

[Jim Williams]

If I understand your post correctly, you are using this transformer to raise the voltage from 208 to 480. if that is the case you would need to ground the secondary side of the transformer to provide a low impedance path to ground so that in the event of a short the overcurrent devices downstream would work properly.