All single phase loads, line to line or line to neutral should be on the "big" transformer, the one that is center tapped. The only exception would be if there are 3 transformers on the pole and that is rare.
Usually red leg delta is done with 2 transformers and if the load is not very well balanced, you will drag that 3d leg around and upset the 240/240/240 relationship.

If your distribution looks like this, be careful with your load balance
[Linked Image from gfretwell.com]

Greg Fretwell