FEET,
As several said above, you probably only need to power the track (or each power district) with just one PowerHouse 180. With a maximum of 18 volts/10 amps you should not harm any engines. New PH180s should become available soon. If you want to run conventional, it can be done through the TIU although it is less convenient than having a transformer with handles. Here is how I would do it, which requires cutting off the plug of the PH180 (or get the adapter wire). Some may want to add a fast blow fuse between the TIU and track, but as GR John stated the PH180 already has a fast CB.
If you really want more than 10 amps to the track, it becomes a lot more complicated. The best way is to use two PH180s through the soon (hopefully) to arrive Legacy PowerMaster 360 (or the old TMCC TPC400). This setup by itself will provide 18 volts/20 amps to the track. First off, you do not want to run this much power through the TIU, so the TIU must be setup in passive mode. Second, I do not know how fast the PM360's CB is, and with this much power going to the tracks I don't want to take any chances. So I would add the very fast, multi setting electronic CB called a PSX-AC. In the drawing I have it set at 15.8 amps because I know my most power hunger train only pulls around 12-13 amps. The 22uH choke is there because the PSX can degrade the TIU signal somewhat.
In both setups I have TVSs. Most of the knowledgeable folks here recommend them, although in the first drawing the TIU's TVS could suffice. For various reasons, I have multiple TVSs on each power run.
I'm positive I'll get some grief on the 20 amp setup but that is my recommendation if you want more than 10 amps.
