Wiring help

Mike one more question. Do you use the (ground/common) on the accessory side of the Z4000 or do you run all the (grounds/commons)  of the track side. Thanks Paul

On a Z4000 the (4) black terminals (commons) are all tied together. An ohm meter should show this to be true.  The pictures, above, show both accessory and track commons together, which works for some track(wheel linked) common activation of devises like crossing gates. For an extensive electric detail layout, like mine, it works best to have both track and accessory commons hooked together.

The OP wants to tie the two transformers together with a common ground.  Is it necessary to put the two in phase with each other?

The question would be:  Do you need to have an accessory transformer and track transformer on the same phase, if the common terminals are connected?? 

My answer: All transformers on a layout need to be on the same phase.

Well I thought that would be my last question but now I am a bit lost. Off the Z4000's I have run my wires from each handle on the transformer to the front side of the two TIU's. Two wires from each track. The back side would go to each track and all the commons to a universal combination of all the commons. Too much??? Am I over thinking. Thanks Paul 

Paul, I would say yes.  But I'm going to defer this answer to Barry Broskowitz. who is the resident expert on DCS wiring.