If thats what he did then thats not right as the others have said. Two options are to change out the transformer to a 208->24V version or pull a neutral. If the transformer is small which it usually is for control circuits, this might be the cheapest correction.

If he pulled a ground in the conduit (which he probably didnt since he is doing the stunt jumpering the neutral and the ground) and if the ground wire is large enough (#4 or larger) and insulated and it is a metal conduit run, e.g. EMT, IMC, Rigid, then you may retape it white and land it on the neutral strip in the panel. The conduit, per code, is an acceptable EGC. However, the machine specs might require the conductor.

People here are going to hang me for suggesting the last solution [Linked Image]