I have never tackeled that one but I thought that each transformer needs to be treated as a stand alone installation, meaning you could not use a common electrode. Building steel is one good option a few points to ponder as codewarrior said. I have multipal transformers in my facilities each treated as a stand alone unit. They put off a lot! of heat so keep that in mind when you do your install and future expansion options. I have several electrical rooms that I am looking hard at adding some form of additional ventilation to cool the area. Also if there is a load factor noise is a consideration as well. Put them on a load and they will hummmm right along and drive clients nuts.
