Could someone give me a quick overview of what to be on the lookout for when a transformer is used as a wye-delta step up transformer?

Background: I am a customer of a PCB fabrication house that has a large solder reflow oven. While I was there the oven kept tripping out seemingly do to power quality issues, and the owner said that this happens frequently. I was not there as an electrician, and it would be inappropriate for me to attempt to do any work on this equipment or in this facility. But as a favor to the owner, I would like to understand what to be on the lookout for, so that I can explain it to him and he can ask the right questions of his EC.

I noticed that the feed to this oven was supplied by a dry type transformer (didn't catch the KVA rating, looked to be at least 100KVA) of the sort normally used as a step down transformer. However the transformer is being used step-up, to supply 480V to the oven. The primary is thus wye connected and the secondary is delta connected. I do not know if the primary neutral is connected to the supply neutral or ground.

Given this state of affairs, what are the issues?

My short list:
The ungrounded secondary can cause problems for neutral connected transient voltage suppression, especially if there is capacitive neutral current from an adjustable speed drive.
If there are ungrounded control transformers internal to the apparatus, they may require a grounded supply for safety (there is what seems to be a 120V computer system running the oven...possibly from a separate supply?)

I don't believe that ground fault detection is required for 480V ungrounded delta supplies...but would it be a good idea? (Duh.)

(Note: I posted this question to electrialmatters...silence [Linked Image] )

-Jon